We will approach potential service providers directly if a specific requirement is identified. Intertrip services are required as an automatic control arrangement where generation may be reduced or disconnected following a system fault event.
Technical requirements for the system to generator operational intertripping scheme will generally be defined at the time connection agreements are being established
The requirements are governed by the Grid Code (CC.6.3.17), which sets out the circumstances where we may require that an intertrip facility of this type be installed as a condition of a connection offer.
Scheme specific details are included in the relevant bilateral connection agreement between us and the connecting party.
Commercial intertrip schemes may be applied to existing and new power stations by agreement.
The service requirements are specific to the location of the intertrip and requires an instantaneous tripping mechanism.
Once a provider is contracted to provide an intertrip service they must make the service available at all times throughout the contract term.
The network conditions including generation background, planned and unplanned transmission outages will determine which provider we wish to arm and when. We then notify the provider.
Frequency of dispatch
When we issue a request to the station to arm, the station will be required to switch in the intertrip scheme to allow signals to pass from the intertrip scheme to the relevant circuit breakers. Once the scheme is armed, the station could then trip (cease output) in response to a fault on the relevant circuits.
It is difficult to forecast the likelihood of arming, as a number of factors will influence this. These are the prevalence of constraints within the relevant part of the transmission network and the effectiveness and economics associated with the operational tools available for managing these at any given time. Instances of tripping are very infrequent and should reasonably be considered to be very low risk.