Who can participate?
External Transmission (interconnected) System Operators.
Service Description
SO to SO services are provided mutually with other Transmission System Operators connected to the GB Transmission System via interconnectors. The inter-connector agreements set out the commercial arrangements and operational circumstances under which the flow on the inter-connector can be managed post interconnector gate closure. It also establishes the arrangements by which reciprocal emergency assistance can be requested and delivered.
The agreement allows for the submission of a buy and sell price by each SO. When services are requested by National Grid they are cleared at the prices submitted by the other SO and vice versa for the services requested by other SOs. At present each SO submit a single pair of prices that cover the price of utilisation (for volume) for the subsequent calendar day.
The SO to SO service covers two balancing services, Constraint Management and Balancing (CMB) and Emergency Assistance.
CMB provides a commercial means for each SO to vary the transfer from the scheduled flow. It is available (unless declared unavailable) up to a pre-defined level. SO’s can however withdraw availability or re-declare limits, if necessary, to safeguard system security. Service terms for CMB are reciprocal.
Emergency Assistance is used as a last resort. When a SO is suffering from a shortfall of generation then, it can call for Emergency Assistance from the other SO either up to a pre-defined level, or the Maximum Capability of the Interconnector (whichever is reached first). The service is assumed to be available from the other SO unless the other has withdrawn its availability. (Availability can only be withdrawn under circumstances of a critical condition on the other Providers system). The service terms of Emergency Assistance are entirely reciprocal.
Why is it needed?
The CMB arrangement provides access for both SO’s to any residual capacity in both directions, to be used in the event of a system requirement (either transmission related or to maintain operating reserve). Emergency Assistance service is important in maintaining security of supply.
Major Technical Requirements
Intraday Limits: Users must comply with pre specified Intraday Limits. Upper and lower limits encompass the sum of Users’ Nominations for all Settlement Periods. Each SO must also specify their price to increase/decrease the transfer.
Reference Programmes: The transfer schedule is produced from the Sum of Nominations, including transfer volumes for CMB and Emergency Assistance that can actually be technically delivered by the equipment. Any interchange is superimposed on the energy trades already agreed by Interconnector Users and therefore has no effect on any interconnector user.
Procurement Process
National Grid has contractual arrangements in place with RTE (France) and SONI (Northern Ireland). National Grid utilises the balancing services available through this agreement in a similar manner to all other balancing services available. The merit order cost of energy, the required lead time for activation (and associated certainty of use) and the implications for levels of system availability are all considered in the determination of whether or not to procure cross border balancing services.
Payment
Payment Structure:
Constraint Management and Balancing: CMB price (£/MWh) is notified daily. The interconnector prices submitted by RTE, SONI and National Grid are published on the “system warnings and other messages” page of the Balancing Services Reporting Service web site. The prices are published on a daily basis at approximately 18:00 and cover the subsequent 23:00 to 23:00, 24 hour period.
Emergency Assistance
EA price (£/MWh) is the higher of the agreed contracted price or the previously notified Constraint Management and Balancing price.
BSAD: Not Applicable
ABSVD: Not Applicable
Summary of Further Information
Grid Code BC2.9.6