14th July
2016
Ex Ante
Reference Price –
Initial Draft Legal
Rules
1
Release Date
14/07/2016
Version No.
1.0
Summary of Changes
Initial legal draft for publication to market rules working group.
INITIAL DRAFT LEGAL RULES
The purpose of this Initial Legal Draft is to describe the proposed rules for the calculation of
the Market Back Up Price and the Curtailment Price. The Market Back Up Price is used in
Imbalance Pricing on occasions where the QNIV is zero and may also be used for Administered
Settlement. The Curtailment Price is used to settle curtailed quantities at the price that they
traded in the ex-ante markets.
In the Plain English Document on this topic, an index price approach was being adopted for
both the Market Back Up Price and the Curtailment Price. Based on comments received, we
have now split the approach. For the Market Back Up Price, we still calculate an index price
based on a reference quantity of the most recent trades. This reference quantity is
parameterised and set from time to time by the RAs. For the Curtailment Price, we now
calculate a price for each Generator Unit based on all its ex-ante trade volumes.
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I-SEM Rules
Trading and Settlement Code
Calculation of Ex-Ante Reference Prices
Initial Legal Draft
14/07/2016
1
A. CALCULATION OF EX-ANTE REFERENCE PRICES
A.1.1
Market Back Up Price
Note to Rules Working Group
The below calculation of the Market Back Up Price is based around the following steps:
1. Setting of the Reference Quantity over which the Market Back Up Price is to be
calculated.
2. Taking the ex-ante trades, converting any q quantities (MW) to Q quantities (MWh) by
applying the lesser of the Imbalance Settlement Period Duration and the trade duration.
3. Taking the weighted average of the reference quantity of most recently traded quantities
applicable to that Imbalance Settlement Period.
A.1.1.1
The Market Back Up Price Average Reference Quantity (QMBUPAR) is a
value determined by the Regulatory Authorities from time to time. The Market
Operator shall publish the approved values within 5 Working Days of the
Regulatory Authorities’ determination or four months before the start of the
Year or other period to which the value is intended to apply, whichever is
later.
A.1.1.2
For each Imbalance Settlement Period γ, the Market Operator shall calculate
the Market Back Up Price (PMBUγ) as the volume-weighted average price of
the QMBUPAR of the most recently traded Intraday Trade Quantities
(qTDAxuh) and Day-Ahead Trade Quantities (qTIDxuh) for the Imbalance
Settlement Period γ, where QMBUPAR is the Market Back Up Price Average
Reference Quantity.
A.1.1.3
For the purposes of the calculation set out in A.1.1.2, the Market Operator
shall multiply the Intraday Trade Quantities (qTIDxuh) by the lesser of the
Imbalance Settlement Period Duration (DISP) and the relevant Intraday
Trade Duration (DTIDx) and Day-ahead Trade Quantities (qTDAxuh) by the
lesser of the Imbalance Settlement Period Duration (DISP) and the Dayahead Trade Duration (DTDAx).
A.1.1.4
For the purposes of the calculation set out in A.1.1.2, where the Intraday
Trade Quantities (qTIDxuh) and Day-Ahead Trade Quantities (qTDAxuh) for the
Imbalance Settlement Period γ are not available, the Market Operator shall
use values from the most recent Imbalance Settlement Period for which
those quantities are available.
A.1.2
Curtailment Price
Note to Rules Working Group
The below calculation of the Curtailment Price is based around the following steps:
1. Taking the ex-ante trades, converting any q quantities (MW) to Q quantities (MWh) by
applying the lesser of the Imbalance Settlement Period Duration and the trade duration.
2. Taking the weighted average of price for all quantities applicable to that Generator Unit u
for the Imbalance Settlement Period.
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A.1.2.1
For each Imbalance Settlement Period γ, the Market Operator shall calculate
the Curtailment Price (PCURLuγ) for each Generator Unit u as the volumeweighted average price of the Intraday Trade Quantities (qTIDxuh) and DayAhead Trade Quantities (qTDAxuh) for the Generator Unit u for the Imbalance
Settlement Period γ.
A.1.2.2
For the purposes of the calculation set out in A.1.2.1, the Market Operator
shall multiply the Intraday Trade Quantities (qTIDxuh) by the lesser of the
Imbalance Settlement Period Duration (DISP) and the relevant Intraday
Trade Duration (DTIDx) and Day-ahead Trade Quantities (qTDAxuh) by the
lesser of the Imbalance Settlement Period Duration (DISP) and the Dayahead Trade Duration (DTDAx).
A.1.2.3
For the purposes of the calculation set out in A.1.2.1, where the Intraday
Trade Quantities (qTIDxuh) and Day-Ahead Trade Quantities (qTDAxuh) for the
Imbalance Settlement Period γ for Generator Unit u are not available, the
Market Operator shall use values from the most recent Imbalance Settlement
Period for which those quantities are available.
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