National Grid gathers generation availability information from Generators over a variety of timescales via information provision mechanisms established under OC2 of the Grid Code. In accordance with the BSC, this information is reflected back to the market in aggregate format predominantly via the Balancing Mechanism Reporting Service (BMRS).
When assessing and publishing generation availability information against system requirements, National Grid includes an Operational Planning Margin Requirement (OPMR) over above demand forecast. This OPMR is the amount of generation, in excess of demand forecast, that is required to meet National Grid’s Day-Ahead Reserve Requirement.
The relevant provisions within the BSC do not provide for the explicit publication of OPMR, but rather describe the publication of a “Surplus”, being the difference between the overall system requirement (demand forecast + OPMR) and the aggregate available generation.
In response to feedback from Market Participants, and in line with recommendations from National Grid’s Reserve Review, National Grid has undertaken to publish OPMR, and its constituent parts, in a manner which complements the information currently on the BMRS. The intention is to assist Market Participants in understanding and interpreting the generation availability information thereby assisting participants to balance their own positions ahead of Gate Closure. The remainder of this note sets out explanation and definition of the data and the arrangements for publication.
2. Data to be published
National Grid will, on a reasonable endeavours basis, publish the data described below by approximately 15:00 each business day. This information will be published immediately after the publication of Surplus [SPLD] information on BMRS. OPMR data will be published in a standard comma separated value (CSV) format. The data will be available from the following link: www.nationalgrid.com/uk/electricity/data/reserve
2.1 Components of OPMR
OPMR is used as part of the calculation of surplus as published on BMRS and is published in two different planning timescales: 2-14 days ahead and 2-52 weeks ahead.
OPMR comprises the following elements:
(a) Reserve Requirements
- Short-Term Operating Reserve Requirement (STORR)
- Short Term Reserve Requirement
- Reserve for Frequency Response Requirement
- Day ahead Contingency Reserve Requirement
A breakdown of Reserve Requirements can be found in Figure 1. This is the total level of generation required by National Grid for reserve purposes.
(b) Infeasible Generation declared as available
This is an adjustment for generation declaring available via the OC2 process but which will not to be able to export on the day. The reasons for this are split into two separate categories:
(b) (i) Unavailable to the market (or National Grid):
This is Generation that is unavailable for use by the market (also inaccessible to National Grid) due to insufficient secured transmission access rights (e.g. TEC).
In OPMR, an adjustment is made to ensure the declared availability at station level is capped by the secured transmission access rights for that station.
For the avoidance of doubt, the transmission access rights assumed does not include submitted applications which are unapproved.
(b) (ii) Unavailable to National Grid
This is the level of available generation that is constrained from exporting onto the GB system transmission system. This calculated figure will assume the system is intact; exceptions to this are system outages which will result in Health and Safety implications given the return of these circuits to service or cannot be returned to service in reasonable timescales.
(b) (iii) Available only to National Grid in exceptional circumstances
This is the level of available generation that is only available to National Grid in specific circumstances such as specific locational issues or at certain times of system stress, for example when a system warning is in force. This restriction could be related to environmental constraints.
OPMR figure adjusters:
(c) Reduction from Additional Availability (Not declared via OC2)
The level of embedded generation or non-BM availability contracted to National Grid, not notified as part of the OC2 notification process. These volumes are form part of National Grid’s Day-Ahead Reserve Requirements and are included to be consistent. This increases the level of availability. This does not include contracted volume within the Maximum Generation (MaxGen) service.
(d) Reduction in Frequency Response Requirement (Contracted Response)
National Grid contracts for Response provision and these services offset the level of Response to be instructed within the Balancing Mechanism. This offsets the underlying Short Term Operating Reserve Requirement, i.e. a negative adjustment.
Items that are included within this total are:
- Firm Frequency Response
- Other Response Provision Services
2.2 Other relevant information
Further information which is already provided on BMRS will be reproduced with the OPMR information to assist market participants in using the data:
Generator Availability
This is the total generator availability (summed at generating unit level) as notified to National Grid (via Grid Code OC2).
Demand Forecast
This is the National Demand Forecast Day (NDFD) as reported on the BMRS website.
Surplus
This is the Surplus (SPLD) as reported on the BMRS website.
SPLD* = Generator Availability – (Demand Forecast + OPMR)
(Demand Forecast includes Station Load)
Maximum Interconnector Import/Export
This is the declared availability of the French & Moyle Interconnectors.
2.3 Pre-contracted reserve
In addition to the information described above, the amount of generation which is declared available via the OC2 process but which is already contracted by National Grid to meet its short term operating reserve requirement will be published as this is “unavailable” to the market
* Assumes French and Moyle interconnectors are at zero