National Grid Gas purchases OM annually, in line with both the requirements of TPD Section K of the UNC and obligations described in the National Grid Gas Safety Case in respect of the National Transmission System. The Safety Case places an obligation on us to maintain OM at levels and locations determined throughout the year.
The OM service is used to maintain system pressures in the period before other system management services become effective (e.g. national or locational balancing actions). Primarily, OM will be used in the immediate period following the occurrence of any of the following, if all other system operator actions are insufficient:
supply loss: terminal, sub-terminal, interconnector, LNG importation terminal;
pipe break (including loss of infrastructure that renders pipe unusable)
compressor failure; or
demand forecast error.
A further quantity of OM is also procured to manage the orderly run-down of the system in the event of a network gas supply emergency (NGSE) while firm load shedding takes place.
OM gas can be provided by a number of operators under current arrangements:
Storage facility operators
Primary capacity holders at storage facilities
LNG importation (with storage) facility operators
Primary capacity holders at LNG importation facilities with storage
Power Station operators (CCGTs) who can reduce demand from the NTS