V11 · Market Operator

1. The market in one picture

The participant volume (V9) teaches what a Balance Responsible Party does with a bid after it leaves the book. This volume is the other chair: the Market Operator. You accept declarations, run the auction, publish one price for the country, write the chalkboard, and later raise the invoice. You do not write a participant’s prices. You do not throw a switch.

Think of SAWEM as a produce market that opens the day before.

Farmers (generators) write sealed notes: “I can sell this many crates, and I will not go below this price.” Buyers (loads) write sealed notes: “I will take this many crates if the price is at most this.” You open every note, fill demand from cheapest supply upward, and announce one crate price for that hour. Every accepted crate trades at that price — not at the number on the farmer’s note. The note only got them into the market.

That auction is the Day-Ahead Market (DAM). It runs once, the day before delivery. Its price is the System Marginal Price (SMP) — one number per hour for the whole country, not one number per zone.

The next morning the weather changes. A solar farm that promised 75 crates can now only deliver 20. The market does not reopen the whole auction. It runs five smaller Intra-Day Market (IDM) auctions that only move the hours still left. The original crate price (the SMP) stays. The intraday auction has its own price, used only for the megawatt-hours that actually moved.

%%{init: {"themeVariables": {"fontSize": "18px"}, "flowchart": {"nodeSpacing": 36, "rankSpacing": 40, "padding": 16}}}%%
flowchart LR
  subgraph yesterday ["Yesterday (D−1)"]
    A["BRPs submit DAM bids<br/>by 10:00"] --> B["MO clears<br/>and publishes by 14:00"]
    B --> C["One SMP per hour<br/>+ two schedules"]
  end
  subgraph today ["Trading Day D"]
    C --> D["Five IDM auctions<br/>revise remaining hours"]
    D --> E["Meters and instructions"]
  end
  subgraph later ["After delivery"]
    E --> F["Indicative statement"]
    F --> G["Initial statement<br/>+ invoice"]
    G --> H["Money moves"]
  end

Three facts that stop most confusion:

1. The DAM price is not per zone. Zones belong to the System Operator. They limit how much can actually flow. They do not set a local energy price. See §6.6.
2. Clearing is not paying. You publish schedules and prices at 14:00 on D−1. The cash leaves bank accounts weeks later, on the Settlement Calendar. See §8.
3. The IDM does not rewrite the DAM bid. It re-uses the day-ahead price curve and changes volume for hours that have not yet started. See §9.

1.1 How to read this volume

If you have twenty minutes, read this chapter, §3, and §11. That is the story: one auction yesterday, five smaller auctions as the day unfolds, money that is calculated immediately and paid later.

If you are answering a participant who says “why was I charged this?”, start at §7 and §8, then walk the same hour in §11.

The current /mo console — panels, queues, Bidding tabs — is §12–§26. Chapter 12 is the map; Market Desk and Bidding share §13; each later chapter is one sidebar room.

Where this is taught. The BRP primer is V9 §1. The System Operator seat is V12. The authority for the numbers in this volume is Market Code Rev 2.3 §§9–10, §14 and §15, written for this chair in docs/references/market/spec/market-dam.md. Nothing here invents a rule. Where the platform has had to interpret a silent clause, the interpretation is named ([D-nn]) and pointed at V9 §17.

1.2 Time and money

Every clock in this volume is SAST, a fixed UTC+02:00 with no daylight saving. D is the Trading Day — the calendar day the energy is actually produced or consumed. D−1 is the day before. A Trading Period is one hour, written as its start: 2026-07-15T18:00:00+02:00 means the hour from 18:00 to 19:00.

Money sign. Positive means the Market Operator pays the participant. Negative means the participant pays the Market Operator. Energy sign: positive means produced, negative means consumed.

The numeric worked day is the same golden fixture every other document uses: Trading Day 2026-07-15, hour 18:00.

2. The people and the things they own

Before a single number, the seats. Confusing them is the fastest way to misread a statement.

Metaphor. The BRP is the stallholder. The Trading Unit is the stall. You are the market master who rings the bell and writes the day’s price on the board. The System Operator is the traffic police who decide which trucks may use which road. The MGC is the town council that set the stall fees and the closing time.

Where this is taught. What a BRP does with those objects is V9. What the System Operator does with the wires is V12 §1. This chapter only names the seats so the rest of the volume can use them without repeating the job descriptions.

3. The clock — when things happen

One table. Times are SAST. D is the Trading Day the energy is delivered.

The DAM bid itself is not settled at 14:00 on D−1. What is published then is the arithmetic of the day — volumes × prices, already visible on the schedule report. The cash waits for the Billing Period. Treat 14:00 as the chalkboard and the invoice date as the till.

Where this is taught. The participant’s day is V1 §4 and V9 §4. Cadence on /mo/cadence is §14 — due / ran / missed for every callable on this table.

4. How DAM bids are submitted

Your problem at intake is simple: every registered Trading Unit must have a declaration at the gate, and none of those declarations may be ones you wrote.

4.1 Who submits

The Balance Responsible Party submits, for each of its Trading Units. You do not write a participant’s prices. You accept, validate, store, and — if the participant is silent at the gate — roll over the last valid declaration.

A bid is not “the company’s bid for Tuesday”. It is “Trading Unit TU-COAL1’s declaration for Trading Day 2026-07-15 and the six days after it”. One company with five units sends five submissions.

4.2 Three doors into the same room

From your side, every accepted declaration is a WB.Sawem.Submission. How it got there is one of three doors.

%%{init: {"themeVariables": {"fontSize": "16px"}, "flowchart": {"nodeSpacing": 28, "rankSpacing": 36, "padding": 12, "subGraphTitleMargin": {"top": 8, "bottom": 26}}}}%%
flowchart TB
  subgraph door1 ["Door 1 — automatic, this platform as BRP"]
    S["Nightly strategy run"] --> W["SubmitDamBids · 03:00 D−1"]
    W --> G["MO Gateway"]
  end
  subgraph door2 ["Door 2 — the participant's own systems"]
    API["PUT /v1/dam/submissions/{date}/{tuid}"] --> I["Intake"]
  end
  subgraph door3 ["Door 3 — your act, not theirs"]
    MISS["Unit silent at 10:00"] --> R["Rollover: yesterday's day 2<br/>becomes today's day 1"]
  end
  G --> SUB["WB.Sawem.Submission<br/>168 periods, stored forever"]
  API --> I
  I --> SUB
  R --> SUB
  SUB --> V["Validation"]
  V -->|accepted| GATE["Counts at the gate"]
  V -->|rejected| ERR["Nothing stored"]

Door 1 — automatic. The organisation using this application has strategy books. Each night those books compute a net position. WB.Brp.BidBuilder turns that into a price curve. An Oban worker runs at 03:00 on D−1 and submits through the same gateway a third-party BRP would use. Those are still the BRP’s bids. You did not choose the volumes.

Door 2 — the Code path. Any BRP may PUT a conformant body to /v1/dam/submissions/{trading_date}/{tuid} as many times as it likes until the gate. Each replace is a new submission_seq. The newest valid version at the gate is the one that clears. The automatic door is just a client of this door.

Door 3 — rollover. If a Trading Unit has no accepted submission at 10:00, you must generate one (§9.3(2)). You do not invent prices. You take the unit’s previous submission and slide the horizon forward one day: previous day 2 becomes new day 1, …, previous day 7 is repeated as the new day 7. The new row is stored with source: :ROLLED_OVER, a pointer at the submission it was copied from, and a staleness_days counter. A unit that misses seven gates in a row is still offering its original day-7 profile. That is legal. It is also how a forgotten outage becomes a live schedule.

Rollover is not a bid the BRP made. It is the market’s rule for silence. The participant can still correct the day in the IDM.

Where this is taught. How a book chooses those reservation prices is V9 §4. The API contract is V13.

4.3 What “submit” actually does

WB.Sawem.Submission.Intake.put/1 is the only write path. It is a single database transaction: all 168 periods, or none; energy limits, or none; a new submission_seq, or a replay of the same seq with the same body.

A late submission (after 10:00, no extension in force) is not stored. The API returns 409 gate_closed and the identifier of the rolled-over submission that was generated instead, plus the next IDM gate as the next opportunity.

A rejected submission is not stored. Validation errors come back with the Market Code clause, a JSON pointer at the offending field, the value, the constraint, and where useful a remedy.

4.4 Blind, binding, replaceable until the bell

• Blind. Nobody sees anyone else’s curve before the gate.
• Binding. An accepted submission is a financial commitment.
• Replaceable until the gate. PUT of the whole 168-period series. Partial patches are refused: a half-applied week is unrecoverable.
• Every version is kept. The operative submission is the highest submission_seq that has not been invalidated. The losers stay, because a dispute about “what did we declare at 09:12?” reads the losers.

4.5 What you do not do at intake

You do not fill in a missing price curve, “fix” an elbow that does not match the registry, accept a 24-period body and pad the other six days, accept a bid for a suspended party, or publish anyone’s curve to anyone else.

You do validate against the registry and the Code, stamp received_at (that instant decides the gate, even if the gate is later extended), keep every version, roll over silence, and tell the participant which rule broke and what to change.

5. The DAM bid, field by field

A DAM “bid” in conversation is three nested things. Name them or the screens will lie.

The rest of this chapter is the Submission. That is what the market determines prices from. The BRP Bid is how this platform produced one — V9 §4.

5.1 The envelope

PUT /v1/dam/submissions/2026-07-15/TU-COAL1

Headers the participant must send: Authorization (own Trading Units only), Idempotency-Key (retries are one submission), X-Sawem-Signature (a financially binding body without a signature is not a submission).

What you store in addition, which they do not send: submission_id, tuid, trading_date, submission_seq, source (:PARTICIPANT or :ROLLED_OVER), received_at (the instant that decides the gate), signature, the rollover chain (rolled_over_from_submission_id, staleness_days), supersession and invalidation stamps, gate_id, and provenance (strategy_run_id, market_rules_id, bid_id) when this platform built the body.

Invalidation is not supersession. A registry change can break an already-accepted future submission. The participant must be told before the next gate. There may be no replacement.

5.2 One period

Each of the 168 rows is one Trading Period.

Idle is legal. A period with no capacity, no consumption and no reserve offer is a declaration of absence. “The unit submitted nothing” and “the unit submitted 168 declarations of zero” look the same on a summary and are different compliance positions. The desk must be able to name both.

5.3 The production price curve — a staircase

A generator does not say “my price is R900”. It says “the first 200 MW cost me R350, the next 100 cost R420, …” — a staircase. The market walks up the stairs until demand is filled. The last step it stood on is the SMP.

Zero-width blocks are dropped, not rejected. A solar farm submits Mingen = E1 = E2 = 0 and E3 = MCR — one step, often at R0/MWh. That is the ordinary renewable bid.

The curve is clamped to the hour’s Declared Available Capacity before it enters the stack.

Price-taker. A registration that has chosen to be a price-taker emits a floor-priced curve. It still has to send a legal staircase; the stairs just sit on the floor.

5.4 The consumption price curve

A generator’s curve answers one question: what does it cost me to make the next megawatt? (§5.3). A buyer’s curve answers the mirror question: what is the next megawatt worth to me?

The market needs that answer for a blunt reason. When there is not enough generation to go round, somebody has to stop drawing. Without prices on the demand side the only tool left is a blackout, which takes power away from the people who need it most and the people who barely notice, in equal measure. A consumption price curve lets a site say, in advance and in Rands: this much I will drop readily, this much only at real cost, this much only at severe cost, and this much I cannot drop at all. The market then sheds in that order, cheapest first, and pays for what it sheds.

The four numbers. One Declared Consumption and three cut lines beneath it.

Why it looks upside down. A production curve climbs: the elbows run from Mingen up to MCR, and the prices climb with them. A consumption curve does the opposite — the elbows descend from DC, and the prices rise as they descend. Both shapes obey the same single rule: the market always takes the cheapest option next. Read from the buyer’s side, the slice nearest DC is the last megawatt you added and the one you would miss least, so it is the cheapest to shed. The deeper the cut, the more it hurts, so the price goes up. Written as the Code writes it: E1 ≤ DC, E2 ≤ E1, 0 ≤ E3 ≤ E2, and CI3 ≥ CI2 ≥ CI1 ≥ 0.

So four slices come out of four numbers:

A worked ladder — TU-IND1, the 90 MW factory.

Data. full_demo · seed 42 · Trading Day 2026-07-15 · hour 18:00 · SAWEM-SPEC §10. The same factory the worked example clears in §11.

The factory sends DC 90, E1 70, E2 50, E3 40, and three prices:

The widths must account for the whole declared draw: 20 + 20 + 10 + 40 = 90 = DC ✓. If they did not, the market would be shedding megawatts the factory never said it would take.

Now walk the price up and watch the factory shrink. Each slice keeps drawing while it is worth more than the clearing price, and stops once the price climbs past it:

That is the whole mechanism. The elastic slices behave as bids in the same auction the generators offer into — a generator bids to supply the next megawatt, a consumer bids to keep it — and the clearing price decides which bids stand.

Must-serve comes from E3 itself, not from the priced slices. That distinction matters when a curve has no priced slices at all: the floor is still E3, so a site that declares no flexibility has its entire draw protected.

The fully inelastic declaration is E1 = E2 = E3 = DC. Every slice collapses to zero width, so there are no priced blocks — nothing to shed, nothing to price. This is the correct form for most industrial sites and for a distributor, and it is a one-field declaration: give the consumption and the platform builds the rest. TU-DIST1 in the worked example is exactly this: 440 MW, no stairs. Zero-width slices are dropped, not rejected — the mirror image of the solar farm’s single-step production curve in §5.3.

Two more mechanical facts, then the judgement call:

• The ladder is clamped to the hour’s DC before it enters the stack, exactly as a production curve is clamped to Declared Available Capacity.
• A consumer marked I is fixed at its whole DC, whatever the ladder says. Flexibility on the period (§5.2) and flexibility in the curve have to agree; I wins.

Choosing the numbers is a commercial decision, not a calculation. The shape above is settled by the Code. What a megawatt-hour is actually worth to a factory is not, and no amount of engineering will tell you. There are three defensible ways to answer it, plus the answer that declines the question — and which one was used is recorded on every curve, as curve_basis on the site’s demand-side profile (WB.Sawem.DemandSideProfile):

The platform implements the shape and leaves the numbers to a configured policy per off-taker category. Recording the basis is what makes a curve auditable: two sites with identical ladders and different bases are not making the same claim, and if a curtailment is ever disputed, which question was answered is the first thing anybody will ask. The safe direction to be wrong in is inflexible — which is why it is the default.

Careful. Both ways of getting this wrong cost the participant, and they are not symmetrical. A site published as inflexible when it could in fact shed load forgoes demand-response revenue — quietly, forever. A site that publishes flexibility it does not have is worse: it gets shed, and it cannot comply.

What you check at intake. The consumption codes in §5.6 are all shape checks — CON_ELBOW1_GT_DC (you priced a slice you never said you would take), CON_ELBOW2_GT_ELBOW1 / CON_ELBOW3_GT_ELBOW2 / CON_ELBOW3_NEGATIVE (the elbows do not descend), and CON_CI1_NEGATIVE / CON_CI2_LT_CI1 / CON_CI3_LT_CI2 (the prices go the wrong way). You cannot check whether R 1,500 is the right number for that factory. Nobody at this desk can.

Where this is taught. The ladder turning into money — curtailment paid at max(own block price, IDP) — is §11.4. On screen, a submitted ladder is the Consumption curtailment order staircase in the declaration drawer (§13.8).

5.5 Energy limits — the reservoir, not the sum

Only energy-constrained units send this: hydro, a battery, a fuel-limited OCGT. For those units the block is mandatory.

The weekly figure is not the sum of the dailies. It is allowed to be less, and for a reservoir it usually is. Σ daily > weekly is rejected (EC_DAY_EXCEEDS_TOTAL). Rollover shifts the array by position: yesterday’s day 2 becomes today’s day 1.

5.6 Validation — every code you will fire

A rejection is a list of these, never a shrug. Each carries its clause, a JSON pointer, the offending value, the constraint, and where useful a remedy.

Two rules you must not add, even though they look tidy:

1. CI1 ≥ CI0. The Code never requires it. Must-run may be priced above the first flexible block.
2. A 24-period submission is “close enough”. It is not. The horizon is seven days.

6. How the market determines the prices

6.1 Who sets the price

Nobody picks a number. You run an auction. The last megawatt-hour needed sets the System Marginal Price. The Market Governance Committee published the cap and the reserve floors months ago; those bound the auction, they do not replace it.

The market master does not decide that tomatoes are R20. The master stacks every seller’s crates from cheapest to dearest, serves every buyer who will pay at least that, and the last crate that was needed is today’s price. A farmer who offered R8 still receives R20 if that is where the last crate sat. How those two piles are actually stacked — crate by crate, for one hour — is §6.3.

6.2 Two schedules, one price

The architecture is the order of the runs. Swap them and somebody is paid twice or not at all.

%%{init: {"themeVariables": {"fontSize": "16px"}, "flowchart": {"nodeSpacing": 28, "rankSpacing": 36, "padding": 12}}}%%
flowchart TB
  SUB["Accepted submissions<br/>+ SO interconnect + SO reserve"] --> UC["Unconstrained run<br/>ignores the wires"]
  UC --> SMP["SMP and the four<br/>reserve system prices"]
  UC --> CS["Constrained run<br/>respects corridor limits"]
  CS --> UNIT["Per-unit reserve costs<br/>and constrained volumes"]
  SMP --> PUB["You review"]
  UNIT --> PUB
  PUB --> BOARD["Publish by 14:00 D−1"]

Solving and publishing are two buttons. An operator who has just re-run a day must be able to look at it first. A pipeline that published as a side-effect of solving would make “let me check that” impossible.

6.3 Building the stacks

This section answers one question: who runs and who draws in each hour. It does not yet produce the published number — reading the price off the result is §6.4.

The whole job is four moves, repeated for each of the 24 hours:

1. Collect the offers. Take every generator’s price staircase (§5.3) and cut it down to what the unit said it could actually do this hour. Add the interconnection import as one free block.
2. Collect the needs. Take every consumer’s protected must-serve load, then the slices it put a price on (§5.4).
3. Match them, cheapest first. Keep taking the cheapest offered megawatt until every remaining need is met. The result is the unconstrained schedule — the plan the country would run if every cable were infinite.
4. Solve it again with the wires on. Where a cable cannot carry the cheap plan, cut the trapped unit back and lift the next-cheapest machine that can get through. The result is the constrained schedule — the plan that actually runs.

Two players do not obey “cheapest first”, and both are deliberate:

• A unit that declared I (inflexible) is placed first, whatever it costs. It promised an exact figure, and the auction does not re-negotiate a promise.
• Must-serve load is never cut. It has no price because it is not for sale. Nothing in this auction is allowed to switch it off.

Two piles of crates

Keep the produce-market picture from §6.1, and make it specific to the stacks.

Imagine the trading floor as a warehouse with two piles, rebuilt every hour.

The supply pile is every crate a farmer will sell, stacked cheap on the floor, dear on top. A coal set does not send one crate labelled “R 900”. It sends a staircase of crates — a cheap bottom shelf, then dearer shelves above (§5.3). A solar farm usually sends one shelf of free crates. The interconnector sends a fixed bundle that costs nothing. You always lift from the floor.

The demand pile is every buyer standing in a queue. At the front: people who must eat — a distributor’s must-serve load, a factory’s protected floor. They have no walk-away price. Behind them: buyers who will pay a lot, then buyers who will pay less (§5.4). If crates run short you do not thin everyone equally. You send home the buyer who values the crate least — the top of the demand pile — and you keep feeding the people who must eat.

You keep lifting supply crates until every remaining buyer is fed. The last crate you actually lifted is that hour’s price. A farmer whose floor crate was R 350 still receives that last-crate price. A peaker whose crate stayed on the floor sells nothing.

%%{init: {"themeVariables": {"fontSize": "16px"}, "flowchart": {"nodeSpacing": 28, "rankSpacing": 32, "padding": 12}}}%%
flowchart LR
  subgraph recipe ["Each hour"]
    A["Clamp every staircase<br/>to that hour's declaration"] --> B["Stack supply<br/>cheap → dear"]
    A --> C["Stack demand<br/>must-serve, then willing"]
    B --> D["Lift from the floor<br/>until the queue is fed"]
    C --> D
    D --> E["Meeting =<br/>unconstrained schedule"]
    E --> F["Re-solve with the wires on<br/>= constrained schedule"]
  end

Three stacking rules that stop most mistakes:

1. Clamp first, then stack. A solar farm whose registry MCR is 75 MW but whose Declared Available Capacity this hour is 60 MW contributes a 60 MW crate, not 75. The emergency shelf above MCR only enters if the hour’s declaration reaches it.
2. A promise sits in the pile even when it is expensive. An inflexible (I) unit is a must-take lump. You do not leave its crates on the floor because a flexible neighbour is cheaper. It promised.
3. Must-serve has no price, and is never shed. The factory’s protected floor is not “a very high bid”. It is not a bid. Nothing in the auction is allowed to take it away.

Worked hour — stack the golden 18:00

Data. full_demo · seed 42 · Trading Day 2026-07-15 · hour 18:00 · SAWEM-SPEC §10. The same cast §11 takes from the door to the chalkboard. Here we only build the piles.

Step 1 — lay every staircase on the bench.

Step 2 — stack supply, cheap on the floor.

Read the pile from the floor upward. Row 1 is the floor — the cheapest crate, and the first you lift. Cumulative is how high the pile has grown after that crate is placed.

Offered supply 655 MW. 20 + 75 + 200 + 100 + 100 + 100 + 60 = 655 ✓.

Step 3 — stack demand, must-eat at the front.

Most willing first. Must-serve has no Rand number. Priced crates follow from dearest to cheapest — that is willingness. Shed order is the mirror: the cheapest priced crate leaves first. Row 1 is the floor of the queue — must-serve, never shed. Row 5 is the top — first to walk away.

Must-serve 480 MW (440 + 40). Elastic 50 MW (10 + 20 + 20). Total demand 530 MW. 440 + 40 + 10 + 20 + 20 = 530 ✓.

Step 4 — lift from the floor until the queue is fed.

Every remaining buyer this hour will pay at least R 1,500. That is above every coal shelf and far above the free crates, so nobody walks away. You only stop when 530 MW have been lifted.

Taken: 20 + 75 + 200 + 100 + 100 + 35 = 530 ✓. Left on the floor: 65 MW of the R 900 coal shelf, and the whole 60 MW peaker. 530 + 65 + 60 = 655 ✓.

The last crate you needed came from coal’s R 900 shelf, 35 MW into a 100 MW step — not on an elbow. That volume (TU-COAL1 at 435 MW) is what §6.4 will read. The meeting itself is 530 MW served.

%%{init: {"themeVariables": {"fontSize": "16px"}, "flowchart": {"nodeSpacing": 20, "rankSpacing": 28, "padding": 12}}}%%
flowchart TB
  subgraph supply ["Supply pile — cheap on the floor"]
    direction TB
    S1["Import 20 MW @ R 0 — taken"]
    S2["TU-PV1 75 MW @ R 0 — taken"]
    S3["Coal 200 MW @ R 350 — taken"]
    S4["Coal 100 MW @ R 420 — taken"]
    S5["Coal 100 MW @ R 640 — taken"]
    S6["Coal 35 of 100 MW @ R 900 — last crate"]
    S7["Coal 65 MW leftover + OCGT 60 MW — still on the floor"]
    S1 --> S2 --> S3 --> S4 --> S5 --> S6 --> S7
  end
  subgraph demand ["Demand pile — must-eat at the front"]
    direction TB
    D1["TU-DIST1 440 MW must-serve — fed"]
    D2["TU-IND1 40 MW must-serve — fed"]
    D3["Factory 10 MW @ R 4,800 — fed"]
    D4["Factory 20 MW @ R 2,600 — fed"]
    D5["Factory 20 MW @ R 1,500 — fed"]
    D1 --> D2 --> D3 --> D4 --> D5
  end
  S6 -->|"piles meet · 530 MW"| D5

Step 5 — write the unconstrained schedule from the meeting.

The piles do not publish a price. They publish volumes.

Energy payments in §7 are struck on these volumes, at the SMP §6.4 reads from the last flexible crate. In this hour that reading is R 900.00 — the walk to the chalkboard is §11.2.

Step 6 — the same piles, a narrower door.

The constrained run does not rebuild different crates. It walks the same warehouse with the wires on. This hour the System Operator says zone Z1 may not export more than 60 MW. TU-PV1’s 75 free crates cannot all fit through that door. Fifteen stay in the warehouse; coal lifts fifteen extra crates from the same R 900 shelf (435 → 450).

That is a different volume, not a different SMP. Energy is still paid on the unconstrained meeting. The fifteen megawatt-hours the wire moved are a separate money line (§6.2, §6.6).

Where this is taught. The full hour — reserve floors, the R 0 constrained-off charge, publish — is §11. The staircases themselves are §5.3 and §5.4.

What you will not see on a public board. This chapter names TUIDs so you can learn the stacking. A published stack — the IDM increment board, the balancing sold/bought piles — shows price and volume only. A TUID on a public stack would publish another participant’s curve.

6.4 The System Marginal Price

§6.3 decided who runs. This section reads the number.

The idea fits in three sentences. Find the machines that had a real choice this hour: they ran, and they could have run a little more or a little less. Among those, find the most expensive one. What that machine charges for the megawatts it was actually given — read off its own staircase, nobody else’s — is the hour’s price, and everyone trades at it.

Said the way Market Code §9.7.2 says it: the System Marginal Price is the incremental price, at the scheduled unconstrained volume, of the most expensive flexible Trading Unit scheduled to run.

Why is the cheap solar farm paid the same number? Because the SMP is not a reward for what you offered. It is the market’s measure of what one more megawatt-hour would have cost. Solar offered R 0 and is paid the SMP; the distributor pays the SMP; the farmer in §6.1 who offered R 8 still received R 20.

Three words in the Code sentence do all the work.

The SMP is one number for the country, for that hour. It is not per zone, not per Trading Unit, not per BRP.

%%{init: {"themeVariables": {"fontSize": "16px"}, "flowchart": {"nodeSpacing": 24, "rankSpacing": 30, "padding": 12}}}%%
flowchart TB
  A["Unconstrained volumes<br/>from the two piles"] --> B["Keep units that actually ran<br/>volume not zero"]
  B --> C["Throw out anyone stuck<br/>I · at Mingen · ramp · reg-down"]
  C --> D["Read each leftover unit's<br/>own shelf at its volume"]
  D --> E["Take the highest of those<br/>shelf prices"]
  E --> F{"Above the cap?"}
  F -->|no| G["That number is the SMP"]
  F -->|yes| H["SMP = cap<br/>and raise the capped flag"]
  C --> I{"Nobody leftover?"}
  I -->|yes| J["SMP = R 0.00<br/>all-inflexible flag"]

The six checks

Do these in order. Do not skip to “last crate on the pile = price” — that shortcut fails at a bend, and it fails when the last crate sat on a machine that was not allowed to set the price.

1. Use the before-the-wires volumes. Read from the unconstrained schedule, never the constrained one. A jammed cable must not leak into the country’s price.
2. Keep only machines that ran. Volume not zero. The idle peaker is out, however expensive its first shelf is.
3. Throw out every machine that had no choice. There are four ways to have no choice:
   • it sits at or below Minimum Stable Generation — on its must-run floor, unable to come down;
   • it declared I for the hour — it promised a fixed figure;
   • it is ramp-bound — it physically cannot move any faster (a fact of the solution, not of the bid);
   • it is held up for Regulation downwards — kept high so it can drop if the grid surges.
4. Ask each survivor one question: what does your own staircase say at the volume you were given? Do not average its cheaper shelves. Do not look at anyone else’s stairs. If the volume lands exactly on a bend, use the bend rule below.
5. Take the highest answer. That is the uncapped SMP. If two units tie to the Rand, the lower Trading Unit identifier is named as the setter — the name must be stable; the price is the same either way.
6. Cap it. Never publish above the Market Price Cap (Annexure 2; this worked day R 5,396.40/MWh). If the raw number was higher, publish the cap and the flag smp_capped — a capped price without the flag is a scarcity signal that has been switched off.

If step 3 emptied the list, stop. The SMP is R 0.00, not the dearest stuck machine, and not “no price” (§9.7.2(5)). Publish all_units_inflexible. An hour in which nothing flexible ran has no marginal cost to show.

Worked hour — read 18:00

Data. full_demo · seed 42 · Trading Day 2026-07-15 · hour 18:00 · SAWEM-SPEC §10.2. The piles that produced these volumes are §6.3.

Step 1 — the volumes the piles already wrote.

Step 2 — throw out anyone who may not set the price.

One candidate remains.

Step 3 — read coal’s own shelves at 435 MW.

TU-COAL1 does not have “a” price. It has four energy shelves (§5.3):

435 is not a bend. It is inside the top energy shelf. The incremental price is R 900.

Step 4 — the highest leftover shelf is the uncapped SMP.

One reading: R 900. Highest of a list of one is R 900. No tie to break.

Step 5 — the cap.

R 900 is below R 5,396.40. The cap does not bind. smp_capped is false.

Step 6 — write the public number.

The chalkboard in §11.2 now multiplies every unconstrained megawatt-hour by this R 900. Cheap solar is paid R 900. The distributor pays R 900. Coal is paid R 900 on all 435 MWh, including the cheap shelves.

Do not re-read the price on the constrained volumes. This hour coal moved 435 → 450 and would still sit on the R 900 shelf — same number, wrong reason. Another hour the wire would change the shelf. The Code keeps that out of the SMP on purpose.

The bend on the stairs

A bend (an elbow) is where one shelf stops and the next starts: 200, 300, 400, and nameplate 500 on this coal set. The Code needs a rule for “exactly on the corner”, because two shelves touch there.

Think of the corner of a staircase. You have just finished a tread. The rule for the SMP is: price the tread you are standing on, not the riser you have not climbed. That is “take the step below” — the platform’s :below elbow convention.

The must-run block (0 → Mingen, R 350 here) never sets the SMP. That is why Mingen is the one bend that is treated the other way, and why a unit sitting there is thrown out in check 3 before the ruler comes out.

When a factory can set the price

The Code sentence is written about generators. It never says whether a factory that was asked to use less may be the dearest leftover unit.

[D-08]. The platform’s shipped default (smp_demand_setting: true) says yes — but only if some of its priced load was actually shed. Then the factory was the last decision. A factory that got every megawatt it asked for is not at the edge, and must not set the price. That is why TU-IND1 was out at 18:00: it drew the full 90 MW.

Every clearing also stores the other reading. The Market Governance Committee can see how often the two disagree, instead of arguing after the fact.

The disagreement is large on the next hour of the same fixture.

Data. Same day, hour 19:00 — SAWEM-SPEC §10.6, the tight hour. Sun down. TU-PV1 is 0. TU-DIST1 declares 520. TU-COAL1 is pushed to nameplate 500. TU-OCGT1 is on at its minimum 60. Import 20. The factory is cut from 90 to 60. Balance: 500 + 60 + 20 = 580 = 520 + 60 ✓.

Who is leftover at 19:00:

%%{init: {"themeVariables": {"fontSize": "16px"}, "flowchart": {"nodeSpacing": 22, "rankSpacing": 28, "padding": 12}}}%%
flowchart LR
  subgraph on ["Shipped default — factory may set"]
    A1["Coal shelf R 900"] --> M1["highest = R 2,600"]
    A2["Factory shed slice R 2,600"] --> M1
  end
  subgraph off ["Literal — generators only"]
    B1["Coal shelf R 900"] --> M2["highest = R 900"]
    B2["Factory ignored"] --> M2
  end

The gap is R 1,700/MWh. Both numbers are stored. The default is the one that makes scarcity visible.

When nobody flexible ran

If every unit that ran is stuck — all I, or all sitting on Mingen — there is no leftover shelf to read. The SMP is R 0.00. You do not take the dearest stuck machine. You do not leave the hour blank. You publish zero and the all-inflexible flag.

That is rare. It is also the rule. An hour with no flexible machine has no last decision to price.

Where this is taught. The 18:00 chalkboard that uses this R 900 is §11.2. The four reserve prices that sit on their floors when the last energy unit still has headroom are §6.5.

6.5 The four reserve system prices

Reserve is a standby promise. The System Operator tells a unit: “stand ready to move at short notice — and because you are standing ready, do not sell that part of yourself as energy.”

Standing ready is work, so it is paid. The only question is how much.

The standby taxi. You ask a taxi driver to wait outside your door all evening, engine running, taking no fares. What do you owe him? At the very least, what the fares he turned away would have paid him. And if the street was empty — there were no fares to be had anyway — he gave up nothing, and you owe him the agreed minimum call-out fee.

That is the whole formula. Per category, per hour:

system price = the dearest unit’s lost earnings, or the floor — whichever is higher.

Four standby promises, four prices:

%%{init: {"themeVariables": {"fontSize": "16px"}, "flowchart": {"nodeSpacing": 26, "rankSpacing": 34, "padding": 12}}}%%
flowchart TB
  REQ["SO reserve requirement<br/>for the hour"] --> Q{"Did anyone give up an<br/>energy sale to stand ready?"}
  Q -->|"no — spare capacity covered it"| FLOOR["Price = the MGC floor<br/>flag reserve_prices_at_floor"]
  Q -->|"yes"| LOSS["Price = the dearest unit's loss<br/>never below the floor"]

Worked hour — 18:00 is an empty street

Data. full_demo · seed 42 · Trading Day 2026-07-15 · hour 18:00 · SAWEM-SPEC §10. The same hour whose piles are §6.3.

The SO wants held ready: Regulating Up 15 MW, Regulating Down 10 MW, Instantaneous 20 MW, Ten-Minute 25 MW. The MGC floors are R 50, R 50, R 50 and R 0 per MW.

Now look back at the meeting. Coal was taken to 435 of its 500 MW, so 65 MW of it stayed on the floor, unsold. The peaker never started at all. Every standby megawatt the SO wants can come out of capacity that was not going to earn anything anyway. Nobody gives up a sale. The street is empty.

So the lost-earnings number is R 0 in every category, and every price lands on its floor:

The board also raises the flag reserve_prices_at_floor (§6.7), so a participant reading R 50 knows it is a quiet hour, not a computed scarcity.

When the street is busy. In a tight hour — think 19:00, when coal is pushed to nameplate and the factory is being cut — every megawatt would have sold. Holding a machine back then costs it real money: the SMP it would have been paid, less what those megawatts would have cost it to make. The dearest such loss in each category becomes the system price, and the floor stops mattering.

Who sees which number. The four system prices are public. Each unit’s own lost-earnings figures are computed on the constrained schedule and go only to that unit’s BRP — publishing them would hand the unit’s cost curve to its competitors.

6.6 Zones do not set the price

A Network Zone is a patch of the grid with a name (Z1 Northern Corridor, Z6 Highveld Load, …). The System Operator may say “this zone may not export more than 60 MW this hour”. That changes the constrained schedule. It does not produce a “Z1 SMP”.

Energy is still paid at the system SMP on the unconstrained volume. Being constrained off is a separate line, settled at the unit’s own offer, not at a local price. In the worked hour a solar farm cut from 75 to 60 MW keeps 75 × R 900 and pays back 15 × R 0 = R 0. That is the Code, not a bug.

Where this is taught. What a zone is, and why the map is provisional, is V12 §2.

6.7 What is published at 14:00 D−1

Events on the stream: prices.published, schedule.published. A BRP that is listening does not need to poll.

6.8 Residual clearing — registered schedules are constants

From stage 11 the day-ahead market clears the residual. A registered forward schedule is a C16-style constant on the energy balance (C1) and is subtracted from each zonal export limit (C17) before spot terms compete for the headroom that is left. It is not a decision variable, and it is not a tie-break: priority over spot is a consequence of the arithmetic.

The published formulation version moves when those expressions change (MO-SPEC-4.3/2026-08). That is a §9.5(7) amendment — the comment window is one month from the publication date, and the formulation may not take effect inside it.

Do not expect the System Marginal Price to stay still when a schedule is registered. Taking volume off both sides of the pool moves the residual merit order. What must stay still is the identity, per Trading Period: registered + residual spot = what the unit cleared with no register. On a binding corridor the schedule is delivered in full and the spot trade is cut to the remaining headroom. If the register alone exceeds the limit, the constrained run is infeasible on C17 — a loud failure, never a silent curtailment of a firm bilateral.

The day-ahead Solution reports residual spot only. Contracted Energy adds the forward base back, which is how §13 still measures deviations against the physical position. The balancing engine is not touched.

7. How the market settles the day-ahead

“Settle the bids” is two clocks sharing one word. Separate them.

This chapter is the chalkboard. §8 is the till.

7.1 The three pots

Every line lands in exactly one account. The kind of the line decides the pot; a caller cannot file an energy payment on the fee account.

A fourth pot, Bad Debt, is for unpaid invoices and default interest. It is not a DAM calculation.

Where this is taught. The participant’s reading of the same three pots is V9 §13. This chapter is the operator’s invariant: the energy pot must print R 0.00 or the day must not publish.

7.2 Energy payment — EPM

EPM = SG × SMP

SG is the unconstrained scheduled volume, signed: plus means produced (you are paid), minus means consumed (you pay). SMP is that hour’s one system price (§6.4).

In crate language: every accepted crate trades at the last-crate price. The note on the farmer’s crate got them into the pile. It does not set what they are paid.

Two things that catch people:

1. Use the unconstrained volume. If the System Operator later cut you from 75 to 60, you are still paid 75 × SMP. The cut is a different line (§7.3).
2. The same price for everyone. A coal plant that offered R 350 and a gas plant that offered R 880 are both paid R 900 if that is where the market cleared. The offer decided whether they cleared, not what they are paid.

%%{init: {"themeVariables": {"fontSize": "16px"}, "flowchart": {"nodeSpacing": 24, "rankSpacing": 30, "padding": 12}}}%%
flowchart LR
  SG["SG<br/>unconstrained MWh<br/>+ produced · − consumed"] --> MUL["×"]
  SMP["SMP<br/>one number<br/>for the country"] --> MUL
  MUL --> EPM["EPM<br/>one signed Rand line<br/>on the Energy pot"]

Worked hour — six lines at 18:00

Data. full_demo · seed 42 · Trading Day 2026-07-15 · hour 18:00 · SAWEM-SPEC §10. Volumes from §6.3. Price from §6.4: SMP = R 900.00/MWh.

Write one line per name. Same multiplication every time.

1. Coal — the last crate, paid like everyone else.

TU-COAL1 was scheduled +435 MWh unconstrained. Its cheap shelves were R 350, R 420, R 640. The last 35 MW sat on the R 900 shelf, so it set the SMP. It is still paid the SMP on all 435 MWh, not only the dear ones.

EPM = +435 × 900 = +R 391,500.00

The Market Operator pays the coal BRP.

2. Solar — offered R 0, paid R 900.

TU-PV1 offered one free crate. That got it into the pile. The payment is still the system price.

EPM = +75 × 900 = +R 67,500.00

The offer decided whether the 75 MWh cleared (it did — it was free). It did not decide the Rand number.

3. The peaker that did not run.

TU-OCGT1 stayed on the floor. Volume is zero.

EPM = 0 × 900 = R 0.00

An expensive unused crate is not a line you pay. It is a blank.

4. The import — not a Trading Unit, still a line.

The System Operator owns the interconnector. The 20 MWh still has to be paid, or the Energy pot would be short by 20 × 900.

EPM = +20 × 900 = +R 18,000.00

Without this row the account holes by −R 18,000.00. Imports are a settlement subject. They are not a TUID.

5. The distributor — a load pays the same R 900.

TU-DIST1 drew 440 MWh of must-serve. Sign is negative: the participant pays the Market Operator.

EPM = −440 × 900 = −R 396,000.00

6. The factory — fully served, still pays the SMP.

TU-IND1 asked for 90 MWh and got 90. Its own priced slices were worth R 1,500, R 2,600, R 4,800. Those numbers decided it would stay in the queue. They are not what it pays.

EPM = −90 × 900 = −R 81,000.00

7. Add them up — the Energy pot must print R 0.00.

Paid out (plus): 391,500 + 67,500 + 18,000 = R 477,000.00

Taken in (minus): 396,000 + 81,000 = R 477,000.00

Volumes: 435 + 75 + 20 = 530 and 440 + 90 = 530. Σ SG = 0. Then Σ EPM = 900 × 0 = R 0.00. ✓

That is the operator’s invariant. The platform checks it on the exact products, before rounding. If it fails, the market cleared wrongly and you must not publish.

%%{init: {"themeVariables": {"fontSize": "16px"}, "flowchart": {"nodeSpacing": 22, "rankSpacing": 28, "padding": 12}}}%%
flowchart LR
  DIST["TU-DIST1 pays<br/>R 396,000"] --> POT["Energy pot<br/>R 0.00"]
  IND["TU-IND1 pays<br/>R 81,000"] --> POT
  POT --> COAL["TU-COAL1 is paid<br/>R 391,500"]
  POT --> PV["TU-PV1 is paid<br/>R 67,500"]
  POT --> IMP["Import is paid<br/>R 18,000"]

8. The wire does not rewrite this chalkboard.

After the piles met, the System Operator said zone Z1 may export only 60 MW. TU-PV1 is cut 75 → 60. Coal rises 435 → 450.

Solar’s EPM stays +R 67,500.00 — still 75 × 900. The 15 MWh the wire moved is §7.3, at solar’s own offer of R 0, and it lands on the Market Balancing pot, not here.

That is catch 1 with numbers. The Energy pot is the unconstrained meeting × the SMP. Nothing else.

Rounding is applied once, to the Rand amount. You do not round 435 or 900 first. Each line also keeps the exact product, because rounding twenty lines on their own can leave a one-cent residual on a set whose exact products sum to zero.

Where this is taught. The same six lines sit on the door-to- chalkboard walk in §11.2. The participant’s reading of the Energy pot is V9 §13.

7.3 Constrained-schedule adjustment — CPP / CSC

§7.2 already paid the plan. This section pays the move.

The Energy pot used unconstrained volumes × the SMP. Then the wires spoke. Some units cannot do what the plan said. Other units have to do more. That difference is not rewritten on the Energy pot. It is a new line, on the Market Balancing pot, at the unit’s own stairs — not at the SMP.

In crate language: you already paid the solar farm for 75 crates at R 900. The door only lets 60 through. You buy 15 crates back. The buy-back price is the number on the farmer’s own note, not today’s crate price. The note said R 0. Buying them back costs R 0. The farm keeps the R 900 on those 15. Coal has to send 15 extra crates. You pay coal’s own shelf for just those 15.

%%{init: {"themeVariables": {"fontSize": "16px"}, "flowchart": {"nodeSpacing": 22, "rankSpacing": 28, "padding": 12}}}%%
flowchart TB
  A["Energy pot already written<br/>SG × SMP"] --> B["Wires move a unit<br/>SG ≠ CG"]
  B --> C["Walk that unit's own stairs<br/>between the two volumes"]
  C --> D{"Moved up on its own axis?"}
  D -->|yes| E["CPP — Market Balancing<br/>pays the integral"]
  D -->|no| F["CSC — participant<br/>pays the integral"]
  B --> G{"SG = CG?"}
  G -->|yes| H["No line at all"]

“Own axis” means megawatts produced for a generator and megawatts consumed for a load. A factory cut from 90 to 70 has a signed volume that rose (−90 → −70) but it lost 20 MW it wanted. That is a CPP — it is compensated — not a CSC.

If nobody moved, there is no line. Do not write R 0.00 for a unit that stayed put. A R 0.00 CSC means “they moved, and their own stairs were worth nothing.”

How to walk one unit

Do these in order.

1. Write SG (unconstrained) and CG (constrained). Same sign convention as §7.2.
2. If they are equal, stop. No line.
3. Face the unit’s own axis. For a generator, compare the two positive megawatts. For a load, compare how much it draws.
4. Walk that unit’s own staircase from one volume to the other. Each shelf: width × that shelf’s price. Add the shelves. That sum is the integral. It is not ΔMW × SMP.
5. Name the kind from the direction (table above). Put the Rand on Market Balancing.

A unit that sent no day-ahead price is walked on a flat R 0 curve (§9.8.2(2)). The integral is still R 0. The sentence on the board is different: no day-ahead price submitted, not own offer was zero.

Worked hour — the wire moves 15 MWh

Data. full_demo · seed 42 · Trading Day 2026-07-15 · hour 18:00 · SAWEM-SPEC §10. Energy lines from §7.2. Zone Z1 may export at most 60 MW.

1. Who moved?

Fifteen megawatt-hours left the solar farm and landed on coal. That is the whole constrained adjustment for this hour. Two lines.

2. Solar — walk 75 down to 60 on its own stairs.

TU-PV1 has one shelf: 0–75 MW at R 0. From 75 to 60 is 15 MW on that shelf.

15 × 0 = R 0.00 → CSC, because a generator was cut.

The board must show the sentence own offer was zero, not a blank. A blank looks like “we forgot the line.”

3. That R 0.00 is the curtailment windfall.

The Energy pot already paid 75 × 900 = R 67,500. The buy-back is R 0. Net for the hour, before IDM:

67,500 − 0 = 67,500 ✓. The fifteen megawatt-hours it will not make are still worth R 13,500 at the SMP (15 × 900). The Code keeps that with the farm (§9.8.2). It is not a bug.

4. Coal — walk 435 up to 450 on its own stairs.

TU-COAL1 stairs (§5.3, §6.3):

Both 435 and 450 are inside the R 900 shelf. One shelf, no bend.

15 × 900 = +R 13,500.00 → CPP, because a generator was lifted.

Not 15 × SMP as a separate idea — it happens to be R 900 because that is coal’s own shelf here. If the extra megawatts had sat on the R 640 shelf, the CPP would be 15 × 640.

5. What if the walk crossed a bend?

This hour it does not. Same coal stairs, two other volumes, to show the ruler — not another auction.

Walk 390 → 410:

20 × 900 would be wrong. You add the shelves you actually cross. That is all “integral” means here.

6. Who has no line?

TU-DIST1, TU-IND1, TU-OCGT1, the import: SG = CG. Nothing to walk. Leave them off this pot.

7. A load, on its own axis — same factory stairs, not this hour.

This hour the factory was not moved. The axis still matters, so walk the fixture curve as if the wires had said “draw 70, not 90.”

TU-IND1 draws 90, with a top slice 70→90 at R 1,500 (§5.4). Forced down to 70:

• On its own axis it is taking less. That is a CPP.
• Walk 90 → 70: 20 × 1,500 = +R 30,000.00.
• Signed energy went −90 → −70. If you keyed the kind off that rise you would label a compensation a charge. Do not.

The factory would be paid for the 20 MWh it was not allowed to use, at what those megawatts were worth to it, not at the SMP.

8. Write the two lines, then look at the pots.

%%{init: {"themeVariables": {"fontSize": "16px"}, "flowchart": {"nodeSpacing": 22, "rankSpacing": 28, "padding": 12}}}%%
flowchart LR
  MBA["Market Balancing"] -->|"CPP R 13,500"| COAL["TU-COAL1<br/>made 15 extra"]
  PV["TU-PV1<br/>cut 15"] -->|"CSC R 0"| MBA
  SO["System Operator"] -->|"recovers R 13,500<br/>as ancillary"| MBA

Solar keeps R 13,500 of SMP on energy it will not generate. Coal is paid R 13,500 for energy it will generate extra. The windfall and the CPP are the same Rand amount this hour because solar’s own offer was zero and coal’s extra shelf was R 900. They are still two lines, two reasons.

9. The System Operator cut is free. Cutting yourself is not.

If TU-PV1 later re-declares 60 → 20 in the IDM, those 40 MWh are priced at the Intra-Day Price, not at its own R 0. In the golden hour that charge is −R 37,800. Walked in §11.4.

That is the commercial fact this section exists to teach: the DAM pays you for the plan; the wire taking it away at your own R 0 costs you nothing; you taking it away yourself does.

Where this is taught. The same two lines sit in §11.2 step 4. The participant’s reading of the windfall is V9 §13.4.

7.4 Additional energy payment — AEPM

The Energy pot pays everyone the capped SMP (§7.2). A machine that offered above the Market Price Cap, and was still told to run, would otherwise be short the difference. AEPM makes that machine whole for the excess of its own stairs over a reference price. It lands on Market Balancing, not on Energy.

AEPM = Σ  width × max(shelf − reference, 0)
       over every scheduled shelf, from 0 to SG

The shipped reference is the SMP ([D-02]). The SMP itself cannot go above the cap (§6.4), so when that unit set the price the two readings agree. They only split when a unit above the cap ran as a cheaper neighbour set the SMP.

Three gates. Fail any one and there is no line — not a R 0.00.

1. It must be a production staircase. A factory’s willingness to pay is not an offer. Paying a load the excess of what it would have paid is a different deal the Code does not have.
2. The unit must be flexible (F). An I unit promised a figure. It is not made whole for a high note.
3. Some scheduled shelf must sit above the cap. Walk only the megawatts that were actually scheduled (SG, unconstrained).

%%{init: {"themeVariables": {"fontSize": "16px"}, "flowchart": {"nodeSpacing": 22, "rankSpacing": 28, "padding": 12}}}%%
flowchart TB
  A["Unconstrained SG"] --> B{"Production · flexible ·<br/>a scheduled shelf above the cap?"}
  B -->|no| N["No AEPM line"]
  B -->|yes| C["Walk 0 → SG<br/>keep only shelf − reference"]
  C --> D["AEPM on Market Balancing"]

Worked hour — nobody is above the cap

Data. full_demo · seed 42 · Trading Day 2026-07-15 · hour 18:00. Cap R 5,396.40/MWh. SMP R 900.00.

1. Who could even be a candidate?

This hour AEPM is absent. That is the ordinary uncongested day. Do not write six R 0.00 lines.

2. Same coal stairs, if emergency had run — not this hour.

TU-COAL1 has an emergency shelf 500–530 MW at R 6,000 (§5.3). This hour’s declaration stopped at 500, so that shelf was clamped off. If 20 MW of it had been scheduled (SG = 520), the shipped walk is against the SMP of R 900:

520 × 900 on the Energy pot would still be the EPM. The extra R 102,000 is only the excess of that machine’s own note over the SMP. The Energy pot does not move.

The other [D-02] reading uses the cap instead of the SMP. Same 20 MW: 20 × (6,000 − 5,396.40) = R 12,072.00. The two readings agree only when the SMP itself is sitting on the cap.

3. A factory must not be paid this.

If you walked TU-IND1’s R 4,800 slice against the SMP you would “owe” a served load tens of thousands of Rand. The first gate stops that. Consumption is out.

Where this is taught. [D-02] is on §25.4. This hour’s empty line sits on the schedule report in §7.6.

7.5 Reserve capacity payments

Reserve is the standby promise from §6.5. This section is the pay cheque: each megawatt that actually qualified, times that hour’s system price, times a performance factor.

PAYRURC = SMPRURC × qualifying MW × PerfAdj
PAYRDRC = SMPRDRC × qualifying MW × PerfAdj
PAYIRC  = SMPIRC  × qualifying MW × PerfAdj
PAYMRC  = SMPMRC  × qualifying MW

Ten-Minute has no performance factor in the Code. The other three use PerfAdj = 1.0 when the System Operator has not said otherwise.

Qualifying megawatts are read on the constrained schedule. A failed band (sitting outside the window the category needs) qualifies zero, not the contracted amount. They land on Market Balancing. The System Operator recovers them.

Worked hour — four hold-backs, one cheque

Data. Same 18:00. Requirements: RU 15, RD 10, IR 20, TM 25. Floors R 50 / R 50 / R 50 / R 0. Street empty (§6.5) → every system price is on its floor.

1. Who was asked to stand ready?

Coal energy + up-reserves: 435 + 15 + 20 = 470 of 500. Feasible.

2. Coal’s three payments.

PerfAdj = 1.0. Prices are the floors.

750 + 500 + 1,000 = 2,250 ✓. That is the R 2,250 on coal’s chalkboard in §11.2.

3. The peaker’s Ten-Minute line.

TU-OCGT1 holds 25 MW offline. The system price is R 0 (floor).

PAYMRC = 25 × 0 = R 0.00

The hold is real. The cheque is zero because this hour’s Ten-Minute floor is zero and nobody gave up a sale. Write the allocation on the schedule. Do not invent a R 50.

4. Who is not paid.

TU-PV1 declared reserve U. TU-DIST1 likewise. TU-IND1 offered some reserve but was not allocated this hour. No contracted megawatts → no line.

5. The pot.

Reserve this hour: +R 2,250.00 on Market Balancing (all coal). Add the §7.3 CPP of R 13,500. MBA energy-side net before IDM: 13,500 + 2,250 = R 15,750. The Energy pot is still R 0.00.

Where this is taught. How the four prices are found is §6.5. The same R 2,250 sits in §11.2 step 4 and on the schedule report in §7.6.

7.6 When the chalkboard is written — the schedule report

The day-ahead lines travel inside the schedule report (§9.10(2)). They are computed when the day is solved. You review them. Then you publish. A pipeline that published as a side-effect of solving would make “let me check that” impossible (§6.2).

They are not an invoice. They are the ingredients of next month’s invoice (§8). A BRP that fetches its schedule already has the chalkboard for that day. The till comes later.

What the report is

One Trading Day. Twenty-four hours. Two audiences:

Events after publish: prices.published, schedule.published.

Worked report — 18:00, as you review it

Data. full_demo · seed 42 · Trading Day 2026-07-15 · hour 18:00 · SAWEM-SPEC §10. Numbers from §7.2–§7.5.

1. Public strip — what the country is told.

2. Own hours — volumes and why.

Σ SG = 0 ✓. The Z1 door is the only binding constraint.

3. DAM lines on the same report — Energy pot.

If that last cell is not R 0.00, do not publish.

4. DAM lines — Market Balancing.

13,500 + 2,250 = 15,750 ✓. This pot does not have to be zero.

5. What each seat is allowed to see after you publish.

They must not see another unit’s stairs or another unit’s lost-opportunity prices.

6. What you check, in this order, before publish.

1. Energy pot R 0.00 on the exact products.
2. Every CSC of zero has a sentence, not a blank.
3. Flags match the hour (smp_capped, all_units_inflexible, reserve_prices_at_floor).
4. The Z1 door is named on solar’s own hour.
5. Reserve megawatts match the SO requirement (15+10+20+25).
6. Then publish. Events fire. Participants fetch.

The same hour, as a follow-along on the Settlement tab, is §13.10 and §11.2 step 5.

Where this is taught. Who may see which artefact is §6.7. The till that later uses these lines is §8.

8. After settlement — charges and notices

8.1 From chalkboard to till

%%{init: {"themeVariables": {"fontSize": "16px"}, "flowchart": {"nodeSpacing": 28, "rankSpacing": 36, "padding": 12}}}%%
flowchart TB
  P["14:00 D−1<br/>schedule + DAM lines published"] --> IDM["IDM lines accrue<br/>through the five auctions"]
  IDM --> M["Meters + instructions<br/>after delivery"]
  M --> BAL["Balancing lines<br/>17:00 D+1 / official D+7"]
  BAL --> IND["Indicative statement<br/>17:00, SD+1 WD"]
  IND --> VER["Data Verification<br/>closes SD+7 WD 17:00"]
  VER --> INI["Initial statement<br/>12:00, BP+5 WD"]
  INI --> INV["Invoice if participant owes<br/>Self-Billing Invoice if MO owes"]
  INV --> PAY["EFT only<br/>participant +3 BD 12:00<br/>MO +4 BD 17:00"]

A statement whose net is exactly zero produces neither document. There is nothing to collect and nothing to pay.

Pay now, argue later. A Settlement Query or a dispute does not hold the invoice. The invoice engine never waits. If the query is later upheld, a correcting document follows. A participant who pays less than the invoice has not made a smaller payment — they have created a Shortfall, whatever they believe they are owed.

Where this is taught. The BRP query journey is V9 §8. The inbox on /mo/dispute is §20. The issued register is §19. The party tax document, the Debit Note Excess, and supply-only refusal: V15 §14. A rerun or a validated dispute arrives as a note, not a replacement invoice: V15 §17.

8.2 How a party is charged — the sign on the statement

Walk one hour for one unit, then zoom out to the month.

1. Energy (EPM). Generator: positive (you pay). Load: negative (they pay). Same SMP.
2. Constrained adjustment. Own-offer integral. Often R 0 for a renewable that was cut.
3. Reserve. Positive if the unit was held for reserve.
4. IDM legs. Accrue through the day; see §9.
5. Balancing. After meters. Not this volume’s subject, but they land on the same statement.
6. MO Charge. Your fee, on its own pot.
7. Net the month. Negative → Invoice. Positive → Self-Billing Invoice.

VAT is applied on the document, not on each line.

8.3 How parties are notified

You do not rely on a person remembering to phone.

The schedule report itself is a notification: §9.10(2) requires the settlement in it, so a BRP that fetched its schedule already has the chalkboard for that day.

8.4 What you must be able to answer

A participant will ask, in this order:

1. Did you receive my bid? Which version counted?
2. What was the SMP, and who set it? Was it capped?
3. What was I scheduled unconstrained vs constrained, and why (which constraint)?
4. Show me the EPM, the CPP/CSC, the reserve lines.
5. What did the IDM then do to me?
6. Where is that hour on my statement, and which invoice did it ride on?
7. When is the money due, and has it been paid?

Every panel in §12–§26 exists so those seven questions have a clickable answer.

9. How the IDM touches the DAM

The Intra-Day Market does not change the DAM bid, does not change the DAM price curve, and does not change the SMP. It changes how much of the remaining day is scheduled, using the same stairs the BRP already sent, and it prices only the megawatt-hours that actually moved.

Yesterday you booked a 75-seat coach at a fare of R 900 a seat. This morning only 20 passengers can travel. The original booking is not torn up. A smaller auction reallocates the 55 empty seats. You still have a 75-seat booking on yesterday’s ticket (that is the EPM). What you do about the 55 empties depends on who cancelled. If the traffic police closed the road, you keep the fare and pay back nothing (constrained sales at your own offer of R 0). If you cancelled, you buy the seats back at this morning’s price (against-instruction, Intra-Day Price flat).

Where this is taught. The BRP Intraday Desk is V9 §5. This chapter is what that desk does to your chalkboard.

9.1 What the IDM is allowed to move

Five fixed auctions, not a rolling “one hour before delivery” window.

A re-declaration for an hour whose delivery has started is refused. It is not a late submission; it is a re-declaration of the past.

The IDM re-clears the remaining hours from the last standing schedule (DAM constrained, or the previous iteration), with updated availability and any new SO constraints. Instantaneous Reserve scheduled day-ahead is not re-optimised, except to replace what a unit has actually lost; replacements earn the day-ahead category price, not a new intraday one.

9.2 What a participant sends — not a new bid

The participant does not send a new staircase. The DAM curve stands. What they send is a new Declared Available Capacity and/or Declared Consumption for remaining hours, optionally a change to the day’s rescheduling-consent flag, and a reason. That is a re-declaration, not a re-bid. See §10.

9.3 The consent flag — the DAM bid that reaches into the IDM

idm_rescheduling_consent on the DAM submission is the standing answer to “may the intraday auction move me?”

The volumes look the same either way. The reason must travel with the movement: “not moved because you asked” and “moved anyway because the SO imposed a constraint” are two different facts.

The flag can also be updated for the day via PUT /idm/rescheduling-consent/{date}/{tuid} without sending a new DAM week.

9.4 On instruction versus against instruction

This is the most misread part of §10. The test is not what happened to the schedule. The test is whether the participant changed its own declaration.

A single hour can carry both legs. A unit that raises capacity by 10 MW and is then scheduled up by 15 has 10 against (it asked) and 5 on (the market took more). Returning one tag for the hour silently overcharges the 5.

Raising capacity is against-instruction only while declared inflexible. A flexible unit that raises capacity and is scheduled up offered the market a choice; the market took it — on instruction.

Ramping spillover counts. A re-declaration at 18:00 that forces a ramp change at 17:00 makes 17:00 against-instruction too, even though nothing was declared for 17:00.

9.5 The Intra-Day Price

Volume-weighted average of the on-instruction increments only, then collared at SMP ± 5 %.

Against-instruction volumes do not enter the stack. A unit that re-declared itself down does not get to drag the price it will then be charged at.

If nothing on-instruction moved, or the signed on-instruction volumes cancel to zero, the Intra-Day Price is the SMP.

The collar is implemented symmetrically ([D-03]): [0.95 × SMP, 1.05 × SMP]. Both the indicative (un-collared) and the applied (collared) prices are published, plus a flag if the collar bound.

9.6 What the IDM does to DAM money

New money is new lines on the Market Balancing Account (IDPM_ON, IDC_ON, IDPM_AGAINST, IDC_AGAINST, IDM_REVERSAL). They do not rewrite the DAM energy account.

9.7 Should a BRP even use the IDM?

Not automatically. Re-declaring a zero-priced renewable converts a deviation that would have been free (SO instruction, or inside the Metering Accuracy Band) into one that costs the Intra-Day Price. The platform’s WB.Sawem.Participant.IdmDecision answers, in this order:

1. If an SO instruction is already expected — carry. Instructed deviation settles at own offer (often R 0).
2. If the deviation is inside the Metering Accuracy Band — carry. It settles at the SMP with no penalty.
3. Past the band, compare magnitude × IDP against magnitude × max(balancing price, SMP) and take the cheaper.

The desk should show that recommendation beside a lodged re-declaration, because the participant will ask “should I have?”.

10. The IDM input, field by field

Two shapes share one lodgement table (WB.Sawem.Mo.IdmLodgement). They are one decision seen twice: what may this iteration do with my unit?

10.1 Re-declaration

PUT /v1/idm/redeclarations/2026-07-15/TU-PV1

What is not on a re-declaration, and must not be added:

The API’s most useful response field is estimated_classification: before the gate, it tells the participant that this reduction will be charged at the Intra-Day Price rather than compensated at their own offer. The price is not known yet; the classification is deterministic from §10(6)–(9).

Last lodgement for the same (unit, date, iteration, period, kind) wins. Two rows for one hour would leave the clearing choosing between them.

10.2 Rescheduling consent

PUT /v1/idm/rescheduling-consent/2026-07-15/TU-PV1

A consent has no Trading Period. It is a statement about the day.

10.3 What you add after the auction

The participant does not send these. The desk must still show them against the lodgement.

11. Worked example — Trading Day 2026-07-15, hour 18:00

Every number below is the golden fixture in SAWEM-SPEC §10. Same day, same hour, same units. If a screen or a test disagrees with this chapter, the screen or the test is wrong.

Data. full_demo · seed 42 · Trading Day 2026-07-15 · hour 18:00 · SAWEM-SPEC §10 / docs/references/market/spec/market-dam.md §11.

11.1 The cast, and what they sent

Five Trading Units, plus a 20 MWh import.

SO reserve requirements for 18:00: Regulating Up 15 MW, Regulating Down 10 MW, Instantaneous 20 MW, Ten-Minute 25 MW. Market Price Cap R 5,396.40. Reserve floors R 50 / R 50 / R 50 / R 0.

11.2 Door-to-chalkboard, step by step

%%{init: {"themeVariables": {"fontSize": "16px"}}}%%
sequenceDiagram
  participant BRP as BRPs
  participant MO as Market Operator
  participant SO as System Operator
  participant PUB as Public / BRP APIs
  Note over BRP,SO: D−1 (14 July)
  BRP->>MO: PUT DAM submissions (by 10:00)
  SO->>MO: Demand, reserves (10:00)
  SO->>MO: Interconnect +20 MWh (13:30)
  MO->>MO: Unconstrained solve
  MO->>MO: Constrained solve (Z1 export 60 MW)
  MO->>MO: SMP = R 900 (TU-COAL1 at 435 MW)
  MO->>PUB: Publish schedules + prices (14:00)
  Note over BRP,SO: D (15 July) 12:00 — IDM iteration 4
  BRP->>MO: TU-PV1 re-declares 18:00 DAC 60 → 20
  MO->>MO: Re-clear remaining hours
  MO->>MO: IDP indicative R 1,412.50, collared R 945
  MO->>PUB: Revised schedule + IDM prices

Step 1 — intake. Each BRP’s body is validated. TU-PV1’s single-block R 0 curve is legal. TU-DIST1’s collapsed consumption curve is legal. Nothing is published yet.

Step 2 — unconstrained stack, 18:00.

How the two piles are stacked, crate by crate, is §6.3. The roll-up for this hour:

Supply, cheapest first:

Demand: 440 (TU-DIST1) + 40 (TU-IND1 must-serve) = 480 must-serve, then every elastic block of TU-IND1 (all worth more than R 900). Total demand 530. Generation needed 530 − 20 = 510: TU-PV1 75 + TU-COAL1 435.

TU-COAL1 at 435 MW is not an elbow, and the unit is flexible → it sets the price. How that reading is done — who is thrown out, which shelf, the cap — is §6.4.

SMP(18:00) = R 900.00/MWh. Not capped. Not all-inflexible. Marginal unit: TU-COAL1.

Reserve: the coal set has headroom, so every lost-opportunity cost is zero. All four system reserve prices sit on their floors: R 50, R 50, R 50, R 0. Ten-Minute (25 MW) is held on the offline OCGT.

Step 3 — energy chalkboard.

How each line is written — SG × SMP, the import, the R 0.00 invariant — is §7.2. The roll-up:

Step 4 — constrained run. The SO flags Z1 exports. TU-PV1 may inject at most 60 MW. 15 MWh moves onto TU-COAL1 (435 → 450). How those two lines are walked — own stairs, not the SMP — is §7.3.

TU-PV1 keeps R 67,500 on 75 MWh it will not all generate. That is the R 13,500 windfall. The Market Balancing Account pays the coal set R 13,500; the SO recovers it as an ancillary service.

Reserve capacity: TU-COAL1 (15+10+20) × R 50 = R 2,250 → Market Balancing Account. How those four cheques are walked is §7.5. AEPM is absent this hour — nobody scheduled a shelf above the cap (§7.4).

Step 5 — publish. You review both schedules, the R 0 CSC (rendered with the sentence “own offer was zero”, not as a blank), the SMP flags, and press publish. Events fire. Participants fetch. The full hour as it sits on the schedule report is §7.6.

11.3 What each party sees at 14:00 D−1

11.4 Intraday iteration 4 — the cost of changing your own mind

Heavy cloud. At 11:47 on D, TU-PV1 lodges:

• iteration 4
• 18:00 declared available capacity 20.000 (was 60 on the constrained DAM)
• 19:00 declared available capacity 0.000
• reason FORECAST_REVISION / “Convective cloud, 11:30 nowcast”

The API’s estimated classification for 18:00: PURCHASE_AGAINST_INSTRUCTION, pricing basis intra_day_price, clause 10(6)(i). The participant is told, before 12:00, that this will not be free.

The re-clear must replace 40 MWh. Coal can rise 15 (to 465, leaving room for the up-reserve it still holds). The other 25 come from curtailing TU-IND1 (90 → 65) — cheaper than starting the OCGT.

On-instruction stack (only):

Indicative IDP = 56,500 / 40 = R 1,412.50. Collar around SMP 900 is [855.00, 945.00]. Applied IDP = R 945.00. collared? is true. Both numbers are published.

11.5 TU-PV1’s running position for 18:00

Effective R 1,485/MWh against an SMP of R 900. Still favourable — because the SO’s 15 MWh cut was free. Had they re-declared the first 15 themselves as well, those 15 would also have cost R 945.

That is the whole DAM–IDM relationship in one unit: the DAM pays you for the plan; the IDM charges you for changing your own mind; the SO changing it for you does not.

11.6 What happens to that hour on the till

The +29,700 does not leave a bank on 15 July. It sits on the chalkboard with every other hour of the Billing Period. On the Initial Settlement Statement it appears as three lines (EPM, CSC, IDC_AGAINST) on two pots (Energy, Market Balancing). If TU-PV1’s BRP is a net creditor for the month, those lines ride a Self-Billing Invoice you pay four business days after issue. If the BRP is a net debtor, they ride an Invoice due in three.

A Settlement Query about the R 37,800 does not stop that invoice. Pay now, argue later. If the query is upheld, a correcting document follows.

Follow along. Seat: mo@webill.net / supersecret. Path: §13.13 walks the same hour on the current Bidding tabs.

12. The sidebar — four operating groups

§§1–11 are the market from this seat — who bids, when the bell rings, how a price is found, and how money is written. This chapter is the current /mo console: the map of fourteen rooms. Market Desk and Bidding are two sidebar items and one chapter (§13); every other later chapter is one sidebar item, tab by tab and field by field.

The Market Operator console is one application with fourteen rooms. They share a left-hand sidebar, branded SAWEM MO. Every room is a first-class route. Nothing important hides behind a second kitchen write. From here on the pages are the thing you press.

Screen: Market Operator (/mo) lands on Bidding → Daily for the current Trading Day. Registry, pairing and standing-data review live one click away at /mo/registry. Fourth landing card when you sign in as MO. This is the other side of every BRP screen in V9 §§2–8.

Follow along. Seat: mo@webill.net with password supersecret. Path: / → Market Operator. You land on Bidding → Daily. You should see four group headings: Market day, Settlement, Eligibility, Reference. Only the group you are working in is open — landing on Daily opens Market day and folds the other three away.

12.1 Why the menu is grouped this way

The sidebar is not an alphabet. It follows the operating clock.

1. Market day — what you do before and during delivery: land, run the cadence, clear the auctions, tell the market.
2. Settlement — what you do after 14:00 and at month-end: meters, stacks, the three bank accounts, queries.
3. Eligibility — who may trade and where they sit: registrations, the register, generator plants, zones.
4. Reference — what the arithmetic is allowed to assume: published parameters, and every immutable run.

Frequent desks sit at the top of each group. Each group is a module row — an icon tile, the module name and a chevron — and the row is a button: click it to open or close that module. Its desks are indented beneath it on a hairline rail, and the desk you are in is a solid amber chip (#mo-nav-metering, #mo-nav-cadence, and so on). The module holding your desk opens itself, so the chip is never hidden, and the console remembers your open/closed shape in this browser. Collapse the whole sidebar with the chevron and the module rows disappear: an 80 px rail of desk icons with hover tooltips.

The action bar sits under the brand: Switch application (the squares icon) back to the landing cards, Sign out, and the chevron that narrows the sidebar.

Quick jump is the search box under it. Type and the sidebar filters as you go — matching desks, or every desk of a module whose name matches, with the matching modules opened for you. Esc or the × clears it and hands the sidebar back to your remembered shape.

Air-traffic metaphor. Market day is the tower radio for today’s flights. Settlement is the airport accounts office after the last wheel is on the ground. Eligibility is the licensing desk — who is allowed to fly, and from which runway. Reference is the published rulebook and the black-box flight recorder: you read it; you do not rewrite yesterday.

Eligibility is drawn third because that is when you notice it on a busy day. In life it runs continuously: a plant filed on Tuesday still changes Wednesday’s solve.

12.2 Shared chrome on every page

Every room reuses the same shell. Learn it once.

A Trading Day is one calendar day in SAST for which the market sold energy. A Billing Period is a calendar month. They are not synonyms. Daily work picks a day; month work picks a month. Default trading date: before 10:00 SAST the picker offers tomorrow (you are still in D−1); from 10:00 it offers today. Default billing month: the previous calendar month.

12.3 Market day — the four items

Path prefix: /mo. Group heading: Market day.

Market Desk is not a second workbench. It is the landing pad. Press it and you are on Daily for the current Trading Day, same page as Bidding. There is no hidden Market Desk LiveView at /mo. The module named MarketDeskLive is the Registry (§22).

Cadence is the timetable. Every Market Code §1.2 callable as due, ran or missed. Run the day and Run the month live here. A miss is a row.

Bidding is the auction room. Six tabs share one date ribbon: Daily, Submissions, IDM, Settlement, Month, Clear.

Notices is the tannoy. GENERAL / SYSTEM_STRESS / PRICE_CAP_EVENT to every participating BRP. Not a System Operator instruction (V12 §3).

12.4 Settlement — the five items

Group heading: Settlement. After 14:00 the chalkboard is done.

Metering is pairing and the D+7 vintage gate. Empty registry is unready, not 100 % of nothing.

Balancing is anonymised stacks, BPB/BPS, the Market Balancing Account. Official is disabled while vintage is unverified.

Accounts is the till: three market bank pots, this month’s cash, who cannot pay, cover, and the cascade. Month is a Billing Period.

Billing is the issued-documents room: register, remittances, corrections, read-only run status. The register names the organisation, writes the period as 1 June 2026, and shows amounts in rands. The eye opens the stored PDF. Issuing still happens on Cadence (§14 — Run the month). The till is Accounts (§18). The walkthrough is §19.

Dispute is one inbox with the org Recon: Data Query, Settlement Query, Settlement Dispute. Pay now, argue later.

12.5 Eligibility — the five items

Group heading: Eligibility. Who may bid, what they filed, where they sit, and who may stand on the carbon venue.

Participants is two boards that are not duplicates. Registrations asks may this seat bid today? Issued Suspension Orders sit on that board as Enforcement, not as extra tabs. Accession register is the §6.2(9) publication clock. Pending Clocks (and Extension Requests, Open Default, Balancing Groups) is the joining and enforcement lifecycle.

Carbon activations is the Q3 / CTD4 queue. A PENDING_APPROVAL carbon participant profile cannot trade, file a pack, or raise a bill until you Activate it (or Refuse it with a reason). Path: /mo/carbon-activations (#mo-carbon-activations).

Registry is Trading Units in force for tomorrow, pairing, and standing-data review.

IPPs is generator sites filed through the standing-data wizard. Certify, Chase, Suspend unit. The Market Operator does not file Trading Units.

Zones is the register in force, coverage, and sites the model cannot place. The CSV goes to the System Operator.

12.6 Reference — the two items

Group heading: Reference.

Rules publishes the twenty-four market parameters and the eight defect switches. A new version is compose → review → confirm. There is no inline edit of the live table.

Runs is every clearing and settlement computation as an immutable record: inputs hash, parameter hash, supersedes, kind. Two runs that differ by one intended input are not the same run.

12.7 How to walk the sidebar on a working day

Do not hop at random. The safe order is eligibility first (is anyone allowed?), then intake, then solve/publish, then the afternoon desks.

12.8 What you will not find in the sidebar

Three rooms people look for here and that live elsewhere.

Handbook bookmarks /mo/dam, /mo/dam/submissions, /mo/dam/idm, /mo/dam/settlement and /mo/dam/month are 301 redirects onto the Bidding tabs. /mo/bid-desk is a 302 onto Daily. They are not extra rooms.

Where this is taught. The Market Code mechanics (why SMP is one price, why the energy pot nets to R 0.00, why a query never holds an invoice) stay in V9. This volume teaches the screens that operate those mechanics.

Data. full_demo · seed 42 · stage S08 (market loop). Demo seat mo@webill.net / supersecret. Worked Trading Day 2026-07-15.

13. Market Desk

The first item in the Market day group is Market Desk. The path is /mo. The icon is a signal. When you pick the Market Operator card on / and sign in as mo@webill.net, this is where you land.

There is no separate Market Desk page. /mo is a 302 onto Bidding → Daily for the current Trading Day. This chapter is the landing hop and the six tabs you land on, so you stop looking for a second room.

13.1 The operator’s problem

You open the console at 09:10 on a Tuesday. You need today’s (or tomorrow’s) pulse in one click: is the gate open, have the System Operator parcels arrived, has anyone solved? You do not want a dashboard of every queue. You want the chalkboard.

That is why Market Desk is a hop, not a home of its own.

13.2 What the hop does

Query params are preserved: date, month, tuid, seq, iteration, period. If date is omitted, the default Trading Day is used — before 10:00 SAST, tomorrow (you are still in D−1); from 10:00, today.

Handbook paths are permanent redirects, not rooms:

13.3 What you see after the hop

The browser title is Bidding. The header sentence is National day-ahead desk — gates, intake, the hourly SMP, and settlement pots. The Daily tab is active. The date ribbon shows the Trading Day the hop chose.

Read Daily as §13.7. In short: four pulse cards in two rows (Clock and gates · Intake health, then Energy and settlement · Notifications), then the Price board — status badge, Low / High / Average / Spread when a curve exists, Solve / Publish…, and the hourly SMP step chart. The energy-account pot must read R0.00 once the day is published.

13.4 Do not confuse two names

The Elixir module WB.WheelingWeb.Mo.MarketDeskLive is not this sidebar item. That module is the Registry at /mo/registry (§22). The landing card still says “Market Desk” in older copy; the sidebar item named Market Desk is the hop to Daily.

BidDeskLive is gone. /mo/bid-desk redirects like /mo. There is no second Clear-day button hiding behind that URL.

Follow along. Seat: mo@webill.net. Path: / → Market Operator, or sidebar Market Desk. You should see /mo/bidding and the Daily tab. Change the date and you stay on Daily. Open Bidding in the sidebar: same page.

Where this is taught. The six tabs, Solve vs Publish, and the 2026-07-15 hour are §13.5–§13.13.

13.5 The six tabs

Path: Market Operator → Bidding (/mo/bidding). Third item in Market day. /mo and /mo/bid-desk land here on Daily (this chapter’s hop, §13.1–§13.4).

One parent, six tabs. The date on the ribbon is shared: change it and you stay on the tab you were on. Handbook bookmarks /mo/dam* land on the matching tab.

This is the auction room. You inspect what arrived, you solve, you publish, you watch the five intraday patches, you read the chalkboard, you roll the month. You cannot type a price.

Where this is taught. Why a bid is 168 periods, why Solve is not Publish, and how the BRP Bid Desk produces the payload: V9 §4. Intraday mechanics: V9 §5. Day-ahead money: V9 §13. This chapter is the screen you press.

13.6 Shared chrome — ribbon and tabs

Browser title: Bidding. Header: Bidding — National day-ahead desk — gates, intake, the hourly SMP, and settlement pots. Icon: hero-presentation-chart-line. Tab bar: #bidding-tabs.

Active tab uses tab tab-active font-semibold. Deep links keep the date: /mo/bidding/submissions?date=2026-07-15, /mo/bidding/idm?date=2026-07-15&iteration=4, /mo/bidding/settlement?date=2026-07-15&period=18.

Ribbon (Bidding.Chrome.bar) is a rounded white bar under the header, not a second page title:

Gate chip. Future day: DAM gate (D−1) — open or closed, plus #mo-gate-countdown and {n} silent. Today: Next IDM gate (open), countdown to 10 / 12 / 14 / 16 / 18 SAST. Past: Gate closed, no countdown.

Solve is not publish. Daily, Settlement and Clear each show both buttons, and they are the same Solve — WB.Sawem.Cycles. On Daily they sit in the Price board toolbar, above the chart, to the right of the day/night key (#dam-price-board-actions). Solve is the emerald play control. Settlement and Clear keep the pair on their own card. After Solve the public noticeboard is still empty. After Publish it is not.

Confirm copy: Publishing makes this the schedule and price set every participant settles against (clause 9.10(1)). It supersedes anything already published for this Trading Day.

Status sentence (@status.sentence):

• This day has not been solved.
• Solved, not published.
• Published at HH:MM. (SAST)
• Published.

A miss on Solve: Solve recorded a miss — a prior step is un-run or an SO input is absent (or there are no accepted submissions for this Trading Day). A miss on Publish: Publish recorded a miss — prices have not been calculated.

You cannot edit a price curve from this seat. If a curve is wrong, the BRP fixes the registry or sends a new sequence.

13.7 Daily — the pulse

Path: /mo/bidding. This is what Market Desk opens.

From md the page is two rows of two pulse cards, then the Price board full-width underneath. Narrow screens stack. Card titles are the ones on the screen, not the old four-across names.

Three traffic lights. Each answers one question only: has the System Operator sent this fact yet? It is not a score of how healthy the numbers look.

Hover on a light lifts it. Each light is a row with a present / unknown / late chip on the right (check, ellipsis, or warning triangle). The lights are not links. The Clock and gates card also carries a summary badge: All present (all three green), Waiting (none late, at least one still unknown), or {n} late.

If the parcel arrives after the due time, the light flips to present. Late means still missing, not arrived late. The teaching of those lights is V12 §1.4.

Constraint note — three honest sentences, never an invented corridor:

• No security constraints have been published. Constrained and unconstrained will match because nothing bound — not because the network was clear.
• Published constraints are empty. The schedules matched because nothing bound, not because the network was clear.
• {n} published security constraint(s) will bind the constrained run.

Intake tiles: Expected, Received, Rolled over. Click any to open Submissions. Hover lifts the row. Counts are units, not MW. The card header shows Units: {n} (expected census). When expected is greater than zero, a Declarations received bar shows received / expected as a percentage. Each row is colour-coded. What a submission is, the other three tiles, and what to look for live on §13.8.

Energy account

On the pulse, inside Energy and settlement (#dam-daily-money-column) — Energy, then Intraday, then Adequacy. The inner card #dam-daily-energy-net is labelled Energy account pot, with Three pots isolated on the right and Must read R0.00 under the figure. The whole card is coloured and is a link to Settlement — hover lifts it; there is no “click through” sentence. This is only the energy pot (EPM — scheduled unconstrained MWh × SMP). It is not Market Balancing, not the MO Charge, and not the three pots added together. The invariant and the arithmetic live in §7.1. Daily asks one question: does the closed loop still close?

A chip next to the Rand figure names the state: Unpublished, Balanced, or Open.

The amount is Chrome.money: R then the exact two-decimal figure, no thousands separator and no space (R0.00, R13500.00, R-12.50). Zero is Decimal equal to 0, so R0.00 and R0.0 do not both appear — it is always R0.00.

Daily does not show the §16(2)(g) rounding residual or the Market Balancing net. Those sit on Settlement (#dam-settlement-mba-net, the rounding residual on the legacy board). Mixing this tile with Balancing or with IDM’s MBA net is how operators invent a “total settlement” that the Code does not have.

Intraday now

In that same stack, below Energy account pot. The inner card is labelled Intraday (IDM). The whole card #dam-daily-idm-now is coloured and is a link to the IDM tab — hover lifts it. There is no Open IDM control. This is whether the intraday market has cleared at least one iteration for the selected Trading Day — not whether the DAM is solved. The DAM constrained schedule stands until an IDM iteration publishes.

The Rand format is the same as Energy account (R0.00, R-19375.00). There is no third empty state — if the board loaded, you get an MBA net, including R0.00. Click the card to open §13.9. Daily does not list lodgements, the next gate, collars, or a per-iteration stack.

Adequacy report (§9.10(4))

In that same stack, below Intraday (IDM). The card is coloured (hover lifts it). It is not a link. The public daily general adequacy report. No participant names. Publish writes it; Solve does not. Daily shows a summary, not the hour-by-hour table. The two DOM ids are exclusive: #adequacy-report or #adequacy-report-empty.

Empty (#adequacy-report-empty, amber, dashed border, warning triangle):

Published (#adequacy-report):

The first sentence is always Public. then the stamp, then a punctuality word.

Daily does not print expected demand, sent-out, consumption, capacity available, capacity allocated to reserves, or SMP from the payload. Those fields exist on the stored report (and on GET adequacy). This card is the pulse: public, when, on time or late, how many periods, contingency unpaid.

Notifications and exceptions

On the pulse, to the right of Energy and settlement. Card #dam-daily-exceptions, titled Notifications and exceptions, with a chip {n} notices (n is the ledger length, including zero). Two lists: exception bullets (risks that are true right now) and the notification ledger (who was told what). They are not the same list. A quiet day can have an empty bullet list and an empty ledger.

Exception bullets — each appears only when its condition is true. All three can show together. There is no “all clear” sentence; silence is the all-clear.

Notification ledger (#notification-ledger) — every notice stored for this Trading Date, oldest first. The Market Operator seat sees the full list, including party-scoped rows. A BRP inbox only sees public rows plus rows that name that BRP.

Empty ledger: a centred check in a green ring and No notices have been recorded for this day. Publish has not written schedule.published, and nothing else has been recorded.

Populated ledger — one row per stored notice (#notification-{id}). Four columns; every value each column can hold:

Time

Event (monospace). The stored event name. Daily does not rewrite it.

Audience

Delivery

Daily does not show channel (event_stream / api / notices / statement) or failure_reason. Failed detail lives on the event incident queue; this table is the receipt list.

Price board

Below the pulse. Card #dam-daily-price-board. Read it top to bottom, as the screen is laid out:

1. Title row. Price board plus a status badge (#dam-daily-price-board-badge): Not solved, Solved, not published, or PUBLISHED. Subtitle: 24-hour system marginal price (R/MWh) · daylight 07:00–18:00 SAST.
2. Stat cards (only when a curve exists): Low, High, Average, Spread — explained card by card below. Hidden when the chart is empty.
3. Toolbar. Sun/moon key #dam-daily-smp-day-night-legend when a curve is drawn (Daylight (07:00–18:00) · Night). Solve (emerald play) and Publish… on the right (#dam-price-board-actions).
4. Chart #dam-daily-smp-chart (380 px). Empty sentence, or the ECharts step line #dam-daily-smp-chart-line. When the run is published and the line is drawn, a green PUBLISHED pill sits on the chart (#dam-daily-smp-published-mark).
5. Footer. Status sentence #dam-daily-price-board-status on the left; Resolution: 1 hour · Currency: ZAR (R) · Timezone: SAST (UTC+2) on the right.

There is no second card repeating the status.

Think of the System Marginal Price (SMP) as yesterday’s tomato price: one number for the whole country, for one hour. Nobody types it. The auction finds the last crate that was needed, and that crate’s price is the hour’s SMP. How the stacks are built is §6. Daily does not re-run that arithmetic. It draws the 24 hourly prices as one anonymous line, and the four cards in the header summarise those same hours.

The four stat cards

The four cards sit in the Price board header, to the right of the title on a wide screen and under the title on a narrow one (grid-cols-2 then sm:grid-cols-4). They appear only when at least one hour has an SMP. If the chart is empty they are absent — not zero. Hours with no price are dropped before any of the four is calculated, so a one-hour teaching run still fills the cards from that one hour.

Every Rand figure is Chrome.money: R then two decimals, no thousands separator and no space (R900.00, R0.00). These are not named TOU bands (Peak / Standard / Off-peak). They are statistics of this Trading Day’s hourly SMPs, the same numbers the step chart draws.

What they share. All four read only the solved (or published) hours on the ribbon’s date. They do not mix yesterday. They are not energy-weighted: a cheap overnight hour and an expensive evening hour count equally, whether 50 MWh or 5,000 MWh cleared. Settlement’s hour table is where you read a single hour; these cards are the day’s envelope.

Low

Slate card. Label Low. Figure in ink. Unit line / MWh.

Low is the cheapest hour of the day — the smallest hourly SMP that was drawn. On a normal day that is a night or early-morning shelf. It is not “the off-peak tariff” and it is not a floor the auction is forced to. If every hour is the same price, Low equals High.

Read it as: the quietest the tomato stall got. A very low Low next to a very high High is a peaky day, not a data error.

High

Amber card. Label High. Figure in amber. Unit line / MWh.

High is the dearest hour of the day — the largest hourly SMP that was drawn. On the teaching day that is the evening shelf (§11 — 18:00 at R 900). It is not the Market Price Cap unless the auction actually hit the cap that hour (capped hours are badged on Settlement, not here).

Read it as: the most expensive crate that was still needed. Hover the chart’s highest shelf to see which clock hour it was; the card does not print the hour.

Average

Slate card. Label Average. Figure in emerald. Unit line / MWh.

Average is the unweighted mean of the hours that have an SMP: add those hourly prices, divide by how many hours were added. Twenty-four priced hours ⇒ sum ÷ 24. A one-hour run ⇒ that hour’s SMP. It is not the median, not a TOU “standard” band, and not MWh-weighted (a 3 000 MWh peak hour does not pull the average more than a 200 MWh night hour).

Read it as: if every hour of this day had been the same price, this is that price. Compare it to Low and High: sitting near Low means most hours were cheap; sitting near High means the expensive hours dominated the clock, not the megawatts.

Spread

Slate card. Label Spread. Figure in sky. Unit line Delta (not “/ MWh” — it is a difference of two prices).

Spread is High minus Low. A flat day is R0.00 (Low = High = Average). A peaky day is a wide Rand gap between the cheapest night shelf and the dearest evening shelf. It is not volatility, not a standard deviation, and not a TOU peak/off-peak ratio. It does not tell you how long the expensive hours lasted — only how far the top of the stairs sits above the bottom.

Read it as: how much the day’s price moved, peak to trough. Average tells you the middle; Spread tells you the height of the staircase.

On the teaching day the evening High is R 900. Low, Average and Spread follow whatever other hours that solve produced — they are not typed; they are computed from the same curve you see.

What the four cards are not. They are not a forecast. They are not the three pots. They do not change when you Publish (the numbers were already the draft SMPs). They disappear rather than show R0.00 when there is nothing to summarise.

What you are looking at. A 24-hour step chart drawn with ECharts. The x-axis is Hour (SAST) (00:00 → 23:00). The y-axis is R/MWh, from zero up. The stroke is ink #212a34, not a coloured series. The line is a step, not a slope: the price is flat for the whole hour, then it jumps (or drops) at the next hour. There are no participant names, no TUIDs, no farm labels. A public wallboard could show the same picture. The plot is washed amber for daylight (07:00–18:00 SAST) and slate for night. Settlement’s 24-hour curve uses a tighter daylight window (07:00–17:00).

What Daily does not draw. Capped hours and all-inflexible hours are not marked here — those badges live on Settlement’s hour table. The y-axis starts at R 0, so a day that is R 900 every hour is a flat line at R 900, not a line glued to the top of the box.

How to read a step. Each shelf is one Trading Period. The price holds until the next hour. If 17:00 is R 640 and 18:00 is R 900, the line runs flat, then up, then flat again. You are not looking at a smooth “demand curve”. You are looking at 24 auction results glued together.

A picture — empty, then the teaching day

Data. full_demo · seed 42 · Trading Day 2026-07-15. Demo clearing uses deterministic TOU SMP bands. Same date ⇒ same stairs.

On that teaching day the evening hour 18:00 is R 900 / MWh, set by coal’s last shelf (§11). The Price board does not write “R 900” on the line. You read shape: night lower, evening higher. Settlement’s hour table is where you read the number.

A few hours from the same teaching day, so you can match the peak on the sketch to a number:

If you Solve a second time, the line is redrawn from the new run. Until you Publish, the public (participants, the adequacy card, the energy account) still treat the previous published day — or nothing — as official.

You cannot drag the line. If an hour looks wrong, the BRP fixes the declaration or the registry and you Solve again. This seat does not edit prices.

Solve and Publish

The two buttons sit on the Price board, in the toolbar above the chart, to the right of the day/night key (#dam-solve, #dam-publish). Solve is emerald with a play icon. Settlement and Clear show the same pair (§13.6). One click here is one click there.

Solve is not Publish. Solve is you running the auction in the back room and looking at the answer. Publish is you pinning that answer on the town noticeboard. Until you pin it, nobody settles against it.

%%{init: {"themeVariables": {"fontSize": "16px"}, "flowchart": {"nodeSpacing": 22, "rankSpacing": 28, "padding": 12}}}%%
flowchart LR
  A["1. Solve<br/>run the auction"] --> B["You look<br/>Price board fills"]
  B --> C["2. Publish…<br/>confirm"]
  C --> D["Town noticeboard<br/>everyone settles"]

What Solve does

Solve (#dam-solve) is always on the Price board. It does three jobs, in order, for the Trading Date on the ribbon:

1. Unconstrained clear — “If the wires could take everything, who would run?” That schedule sets the SMP.
2. Constrained clear — “What may the wires actually carry?” That schedule is what injects. It does not rewrite the SMP.
3. Calculate prices — write the hourly SMP (and the money lines) onto a solved run. Nothing is public yet.

If a System Operator parcel is missing and the run cannot proceed, the flash is Solve recorded a miss — a prior step is un-run or an SO input is absent. The Price board stays empty.

If there are no accepted submissions for the Trading Date, Solve is also a miss (there are no accepted submissions for this Trading Day) — it does not write an empty run and it does not fill the board with a fake flat line. Publish of a run with no hourly prices is likewise a miss, so a blank solve cannot replace a curve that was already on the noticeboard.

If it works, the flash is Both schedules solved and settled. Nothing is published yet.

%%{init: {"themeVariables": {"fontSize": "16px"}, "flowchart": {"nodeSpacing": 20, "rankSpacing": 26, "padding": 12}}}%%
flowchart TB
  S["You press Solve"] --> U["Auction ignoring the wires<br/>this sets the SMP"]
  U --> C["Auction with the wires<br/>this sets who actually runs"]
  C --> P["Write a solved run<br/>still private"]
  P --> Y["Price board: ink step line<br/>Badge: Solved, not published<br/>Publish… appears"]
  P --> N["Energy account pot still —<br/>Adequacy still empty<br/>Participants not told"]

Worked example — you Solve 2026-07-15 at 13:10.

You are mo@webill.net. Date ribbon: 15 Jul’ 2026. Clock and gates shows Trading date 15 Jul’ 2026. Demand / Reserves / Interconnect are present. Badge Not solved. Chart says This day has not been solved. There is no Publish… button. Low / High / Average / Spread are hidden.

You press Solve. The three jobs run. Flash: Both schedules solved and settled. Nothing is published yet.

You have a draft. You can open Settlement and read the chalkboard. You have not yet made it the plan.

What Publish does

Publish… (#dam-publish) only appears when the latest run is solved. After a successful publish the run is published, so the button hides until you Solve again.

It never publishes on the first click. It opens the amber confirm #dam-publish-confirm:

Publishing makes this the schedule and price set every participant settles against (clause 9.10(1)). It supersedes anything already published for this Trading Day.

Publish this run then:

• Stamps the run published (SAST time on the status sentence).
• If this date already had a published run, that old run is superseded, not edited — so “why did my statement change?” still has an answer.
• Writes the public adequacy report.
• Writes schedule.published on the notification ledger (a public row plus a row per party) and tries to deliver those events.
• Makes Energy account read the published energy pot (R0.00 on a good day).

Success flash: Published. Every participant now settles against this run.

Miss flash: Publish recorded a miss — prices have not been calculated. (You pressed Publish without a solved price run.) If there is no solved run at all: There is nothing solved to publish.

%%{init: {"themeVariables": {"fontSize": "16px"}, "flowchart": {"nodeSpacing": 20, "rankSpacing": 26, "padding": 12}}}%%
flowchart TB
  P["You press Publish…"] --> Q{"Confirm?"}
  Q -->|Cancel| X["Nothing changes"]
  Q -->|Publish this run| Y["Pin this run<br/>supersede any older published run"]
  Y --> A["Adequacy card fills<br/>On time or Late"]
  Y --> E["Energy account pot gets a net<br/>R0.00 Balanced or red Open"]
  Y --> N["Ledger: schedule.published<br/>participants are told"]
  Y --> S["Status: Published at HH:MM<br/>Publish… hides"]

Worked example — you Publish the same day at 13:40.

Status still says Solved, not published. You press Publish…, read the amber warning, press Publish this run.

If you had published at 14:10, Adequacy would say Late. The prices would still be published. Late is a fact about this chair, not a second button.

If you Solve again after publish, you get a new solved run. The Price board follows the new draft. The public still sits on the old published run until you Publish the new one (which supersedes).

Follow along. Seat: mo@webill.net / supersecret. Path: Market Operator → Bidding → Daily ?date=2026-07-15 → Solve → read the Solved, not published badge and the ink step line → Publish… → Publish this run. You should see badge PUBLISHED, a green PUBLISHED pill on the chart, Energy R0.00 / Balanced, and Adequacy Public.

The control table, ids, and flashes are listed once in §13.6. Daily is where you use them.

13.8 Submissions — silent and rejected

Path: /mo/bidding/submissions. Date on the ribbon is the Trading Day you are inspecting. Daily’s Intake health card is the three-number headline; this tab is the ledger behind it.

This is intake, not a second Bid Desk. You cannot type a price, add an increment, or “fix” a curve. If a declaration is wrong, the BRP sends a new sequence (before the gate) or corrects in the IDM (after). You accept, refuse, roll silence, and read what was stored.

Where this is taught. Who may submit, the three doors, why a late PUT is not stored, and why every version is kept: §4. The 168-period body, consent, idle hours, energy limits, and every validation code: §5. This section is the screen you press, and what to look for on it.

What a submission is

A submission is one registered Trading Unit’s financially binding declaration for this Trading Day and the following six days — exactly 168 hourly periods. It is not “the company’s bid for Tuesday”. One BRP with five units sends five submissions. The market clears from the operative body: the highest submission_seq for that unit and date that has not been invalidated.

It arrived through one of three doors (§4.2):

1. Participant — a PUT the BRP sent (this platform’s nightly worker is still a BRP client of the same door).
2. Rolled over — the unit was silent at 10:00, so you generated today’s body from yesterday’s remaining horizon (§9.3(2)). You did not invent prices.
3. Nothing stored — they never got in. A rejected or late attempt is not a submission. It lives in Rejected / late attempts below the table. Telling a BRP “we have nothing” when they have a 409 is an operational lie.

Accepted bodies are blind (nobody else sees the curve before the gate), binding, and replaceable until the bell. A 24-period body is refused as a horizon fault, not padded. A financially binding body without a signature is not a submission.

The main table shows one row per unit that has anything stored for the ribbon date — the newest sequence. Older sequences stay in the drawer under Version history. Solve reads the operative rows. If there are none, Daily’s Solve is a miss (there are no accepted submissions for this Trading Day).

What this tab is not. It is not the Price board, not Settlement, not the BRP Bid Desk, and not a place to publish. Filter Superseded is almost always empty on this table: the row is already the newest sequence, so “superseded” is a status you read in the drawer history, not a second row here.

Read the page top to bottom, as the screen is laid out:

1. Six tiles — census, who sent, who was carried, who is broken, how many versions, who is still missing. Explained tile by tile below.
2. Filters — search, source, status, CSV, and Extend (only while the DAM gate is still open). They hide rows; they do not change the tiles.
3. Main table — stored declarations. Empty sentence plus jump links when this date has none.
4. Rejected / late attempts — the intake audit. A 409 is a row.
5. Declaration drawer — one version, read-only.

The Extend the DAM gate form is not a card on this page. It opens from Extend on the filter row, and only while the DAM gate is still open.

The six tiles

Counts are units (or versions), not MW and not Rand. The six cards sit in one row (#dam-submissions-tiles). Daily’s Intake health repeats Expected, Received, and Rolled over and links here. The other three exist only on this tab.

Colours are the same traffic lights as Daily, plus indigo for versions. data-tone on each card is the authority: info sky, ok green, warn amber, incident red, accent indigo.

The tiles do not all add to Units expected. Received and Rolled over count only operative newest rows. An invalidated unit is covered (it has a stored body) so it is not silent — it sits in Invalidated awaiting resubmit. Before you Solve, the identity to hold in your head is:

expected ≈ received + rolled over + invalidated + silent

A leftover of one is worth a look (a newest row that is somehow superseded). A leftover of many means the census and the store have drifted.

Units expected

Tile #dam-submissions-expected. Always sky (info). How many registered Trading Units the market owes a declaration. This is the census, the same Units: {n} on Daily. It does not care whether they have sent yet.

If this is 0, the registry is empty for SAWEM — intake has nothing to count, and Solve has nothing to clear.

Received (participant)

Tile #dam-submissions-received. Unique units whose newest stored body is operative and Participant. They sent (or this platform sent on their behalf). Green when this equals expected; amber when some; red when none — same lights as Daily.

Replaces before the gate do not inflate this tile — five sequences for TU-COAL1 still count as one unit received. The extra sequences sit in Versions today.

Rolled over

Tile #dam-submissions-rolled. Unique units whose newest stored body is operative and Rolled over. Amber when this is greater than zero — carry-forward is a look, not an incident. Zero rolled is green: everyone who is covered sent.

A rolled row is still a real submission. Solve will use it. The BRP can still correct the day in the IDM. What you look for is staleness on the row, not the badge colour.

Invalidated awaiting resubmit

Tile #dam-submissions-invalidated. Red when the count is above zero, otherwise green. Unique units whose newest stored body was broken by a registry change after it was accepted. They thought they were done. There may be no replacement. Daily’s Notifications card repeats this as {n} unit(s) invalidated and awaiting resubmit when the count is above zero.

Invalidation is not supersession and not a 409. Filter Status → Invalidated and open the row: the Operative? cell carries the clause-7.1(5) sentence and the codes. The participant must be told before the next gate (§8.3).

Versions today

Tile #dam-submissions-versions. Always indigo (accent) — a count, not an alarm. How many submission records are stored for this Trading Date — every sequence, every unit. If Received is 40 and Versions is 40, nobody replaced. If Versions is 90, they iterated. That is ordinary before the gate. After the gate it is a look: who was still replacing, and did a late PUT bounce into the rejected table instead?

Silent at last snapshot

Tile #dam-submissions-silent. Amber when anyone is missing, otherwise green. Registered units with no stored submission at all for this date. The ribbon’s gate chip on a future day shows the same count as {n} silent.

Before 10:00 on D−1, silence is ordinary — they have not sent yet. After the gate, silence is the thing rollover is supposed to have filled. A number still above zero means either rollover has not run, or the unit had no previous valid body to roll (new registration, never submitted). Those units will not appear in the main table. They also will not appear in Rejected / late attempts unless they tried and failed. Filter will not find them. The tile is the list length; open Registry if you need the names.

What to look for

Walk the tiles first, then the rejected table, then the amber rows. Do not start in the drawer.

What you can ignore. A Participant badge. Seq 1 with no replaced note. Staleness 0. Horizon 168. Energy limits n/a on a coal or solar unit that is not energy-constrained. willing consent. Those are the ordinary healthy row.

What this tab will not show you. Capped hours, the SMP, the three pots, or who set the price — that is Daily and Settlement. Who is suspended and may not bid — that is Registry; their PUT never becomes a row here (it becomes a rejected attempt).

Filters (#dam-submissions-filters):

Main table (#dam-submissions-table):

Empty: No submissions were stored for {long date}. The table (and its column headers) and CSV are gone. When other dates have intake, #dam-submissions-intake lists them as cards grouped by weekday Monday–Sunday (#dam-submissions-intake-monday … -sunday). Each card #dam-submissions-jump-{ISO} reads {day} {Mon} '{yy} — 24 Aug ’26, not the ISO date.

CSV (#submissions-csv) sits on the right of the Search / Source / Status card, with Extend (#dam-submissions-extend) immediately after it while the ribbon date is today or the DAM gate is still open. CSV is hidden when this date has no stored submissions. CSV exports accepted and refused rows: /mo/bidding/submissions.csv?date=…. Columns: kind, tuid, brp, source, seq, status, received_at, reason, codes. Kind is submission or rejected. Use this when a BRP says they sent something you cannot see — the refused line is the receipt.

Extend is amber, same height as CSV. It is shown while the ribbon date is today (the chrome then reads the next IDM gate) or still in D−1 with the DAM gate open. Once the DAM gate chip reads closed, or the Trading Date has passed, the button is gone and there is no Extend the DAM gate card at the bottom of the page. Clicking Extend opens the modal (#gate-extension-form). Cancel, the X, the backdrop, or Escape close it.

Rejected / late attempts (#submissions-rejected): Time · TUID · Reason · Codes. These are not submissions. A 409 gate_closed is a row; so is a horizon fault and a sequence conflict. Empty: No rejected or late attempts for this Trading Date. This is the intake audit. Row ids are intake-audit-{id}. The TUID (when known) links to Registry.

Extend the DAM gate (§9.3(3)) lives in that modal, not as a card under Rejected / late. Reason, authoriser and published_at are required. An extension is judged at receipt — it cannot resurrect an earlier rejection.

Submit: Extend gate. Success: Gate extended under clause 9.3(3). A save without published_at fails.

Declaration drawer (#submission-drawer). Open from a row or ?tuid=&seq=. Branded header (#submission-drawer-header) in Webill indigo with the amber clipboard mark, sticky — the panel is long and the header stays put while the body scrolls under it, so you never lose track of which declaration you are reading. Eyebrow Declaration, then {TUID} · seq {n}, then a sub-line reading {Participant | Rolled over} · Trading Date {weekday d Mon yyyy} · {received stamp} — the Trading Date is spelled out in full, e.g. Wednesday 19 Aug 2026, because the weekday is what tells you whether the day is a business day.

Footer: Registry Mingen {mwh} · MCR {mwh}. Increments are not editable on this desk. Empty curves: No production curve. / Must-serve only — no priced blocks.

Nothing on this drawer is left as an abbreviation. Three affordances, and you need only one of them:

1. Hover a label. Every dt in Envelope and Pinned hour carries an information mark and a one-sentence definition — DAC gives you Declared Available Capacity — megawatts this unit says it can produce this hour.
2. Read the value. A coded letter is never left bare: F is followed by Flexible, I by Inflexible, A by Available, U by Unavailable, each in a badge tinted by what it means (I amber, A green, U grey). Staleness reads 0 — current or 3 gates missed rather than a naked integer.
3. Open the legend. What these labels and letters mean (#submission-drawer-legend) sits under the pinned hour, collapsed. It spells out DAC, DC, F, I, A, U, the three reserve categories, Consent, Staleness, and Mingen / MCR in full — including that I is a commitment and not a ceiling, and that an A against a category the System Operator certified at 0 MW is refused at intake. Use this one on a touch screen, where hovering is not available.

The F / I sentences are the same text the BRP’s own submission desk shows, so a dispute about what was declared cannot turn on the two seats having been told different things.

Hour-band colours. A block is one Trading Period, addressable as #submission-hour-{h} where h is the SAST start hour. Declared hours are split by the sun: amber for daylight (06:00–18:00) and indigo for night. State outranks the clock — an inflexible :I hour stays dark grey and an idle hour stays light grey whatever the time, so a solar unit reads as grey night shoulders around an amber day. The pinned hour carries an indigo ring. The legend under the band names all four. Hovering gives {HH:MM} · {day | night | idle | inflexible}.

Follow along. Seat: mo@webill.net / supersecret. Path: Market Operator → Bidding → Submissions ?date=2026-07-15. Read the six tiles, then find TU-PV1. Horizon 168, Source Participant, no increment form. Open View declaration. You should see seven horizon-day buttons and a 24-block hour band. Golden units: TU-COAL1, TU-PV1, TU-OCGT1, TU-DIST1, TU-IND1. Then open Rejected / late attempts — on a clean teaching day it is empty; that emptiness is the receipt that nobody bounced.

13.9 IDM — five patches, no names

Path: /mo/bidding/idm. Optional ?iteration=4. Optional &period=18:00 opens the auction drawer.

The DAM has locked tomorrow’s (or today’s) schedule. Weather and load still move. The Intra-Day Market is five short auctions that patch the remaining hours — they do not tear up yesterday’s ticket. You do not type a price here. You do not lodge a re-declaration. You watch whether the five bells rang, who asked to move, what the market actually moved, and whether the Market Balancing Account paid out or took in.

That is a different job from Daily. Daily’s Solve / Publish are the day-ahead pair. This tab has neither. The five auctions fire from the clock. Your chair is to see them, explain them, and chase a miss.

Where this is taught. What a BRP sends, why re-declaring your own capacity costs money, the ±5 % collar, and carry-versus-re-declare: V9 §5. What the IDM is allowed to move, consent, on- versus against-instruction, and why EPM and SMP do not change: §9. Daily’s pulse card is §13.7 Intraday now. This section is the screen you press, what the clock already did, and what — if anything — you still have to do by hand.

What the IDM is

The IDM is not a second day-ahead market. It is not a rolling “one hour before delivery” window. It is five fixed auctions on the Trading Day (the first of them the evening before), each of which may still move only the hours whose delivery has not started.

A re-declaration for an hour whose delivery has started is refused. It is not a late DAM submission; it is a re-declaration of the past.

What a participant sends is a patch, never a new staircase. The DAM price curve stands. They change Declared Available Capacity and/or Declared Consumption for remaining hours, optionally the day’s rescheduling-consent flag, and a reason. You cannot re-price mid-day. If you could, you could watch the stack form and then move the price you are about to be paid at.

The IDM re-clears the remaining hours from the last standing schedule (the DAM constrained schedule, or the previous iteration), with updated availability and any new System Operator constraints. Instantaneous Reserve scheduled day-ahead is not re-optimised except to replace what a unit has actually lost; replacements keep the day-ahead category price.

What the IDM does not change. The DAM bid. The DAM price curve. The SMP. The energy-account pot (EPM). New money is new lines on the Market Balancing Account. A unit walked all the way back to its DAM constrained schedule has a net IDM position of R 0.00.