How balancing offers are screened, quarter-hour by quarter-hour

Day-ahead surveillance reconstructs a merit order, because the order book is not published, and every finding there carries the reconstruction's own error. Here the regulatory feed publishes the individual balancing energy bids, so this view reads the ladder rather than estimating it. There is no model error to disclaim.

What the publication does not carry is identity. It can show that one price step carried the volume that set the price; it can never show whose step it was. Every finding attributes to a step in a ladder.

Every quarter-hour of the delivery day is screened, in both directions, whichever one was actually called. The inputs are already in memory and the screens are arithmetic, so the whole day costs no extra upstream call - and a control that chose one direction would only hide the other.

The ladder

Every offer published for the quarter-hour, cheapest first, per balancing product. Products are called in sequence and each keeps its own price axis.

The trailing band

The distribution of the SAME quarter-hour across preceding delivery days. A screen fires when a reading clears that band, so a volatile period needs a larger move than a quiet one - a period is measured against its own history rather than a fixed constant.

What is not on the ladder

Not everything that balances the zone comes off it. Activation by component splits what actually answered, and a product that supplied nothing has no settled price to be measured against, so its price-relative readings are absent rather than zero.

Nothing crosses on the ladder charts, and that is correct rather than a rendering gap: only one direction is called in a quarter-hour, and the reference lines are the settled marginal prices rather than a point where supply met demand.

What answered

The activation split by component. The products are called in sequence, and not all of what balances the zone comes off this ladder at all.

Each product's ladder, on its own terms

Offered, unavailable and priced, per balancing product. A product that supplied nothing has no settled price to be measured against, so its price-relative readings are absent rather than zero.

What fired

The findings for this direction and quarter-hour, each stating what was observed with the numbers in it.

How close every screen came

All three screens listed whether or not they fired. A screen that is silently absent is indistinguishable from one that found nothing, so none of them is ever omitted.

Depth price is read 100 MW into each product's own ladder, not 100 MW along the shared volume axis. The products are called in sequence and the second one starts a few hundred MW in, so an absolute depth would land before its first offer and describe a product that had not begun. At or better is defined only for the product the settled price is attributed to, because it is a comparison against a price the other products were not paid.

The strip is every quarter-hour of the delivery day, both directions screened, so the day can be scanned before any one period is opened. Selecting a period changes the ladder below and rides in the URL.

The price chart is the imbalance price per quarter-hour over the system imbalance that drove it. Positive imbalance is the system long, negative is short. The system imbalance is drawn as a bar strip in MW on its own scale beneath the plot: it is never read off the price axis above it, and the legend says so.

Belgium only, and individual bids only from the market platform change of 2024-05-22. Delivery days before that were published under a schema this does not read, which is not a gap in collection - nothing here ever covered that schema.

The publisher holds a rolling two years; a delivery day past that is no longer served and nothing here stored a copy. A day that carried no published bids is reported as a published answer rather than as a failure, and the default view moves back to the most recent day that does carry them, saying so and carrying that day in the link you share.

The bids are as published, so the ladder is not in doubt. The inference from it is. A unit already at minimum stable load, a network constraint, an outage not yet disclosed, a position already hedged: each produces the shapes these screens look for, and none is visible in this data. Verify against outage disclosures before drawing any inference.