Intertrips
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.
The system to generator operational intertrips service may be required as a condition of connection. This is specifically covering commercial intertrips.
Commercial Intertrips
- An additional service negotiated on an ad-hoc basis.
- Allow a higher level of generation onto the system during times of system stress and tight margin.
- Used to manage Britain's transmission system following credible unplanned faults that need to be secured against in accordance with security and quality of supply standards.
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.
Provider availability
Once a provider is contracted to provide an intertrip service they must make the service available at all times throughout the contract term.
Service dispatch
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.
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.
Commercial intertrips may be specified at the time of:
- a connection agreement being entered into; or
- negotiation on an ad-hoc basis.
This service can be delivered from any generation connected to the transmission system.
For the system to generator operational intertripping schemes, section 4 (Balancing Services) of the Connection and Use of System Code (CUSC) specifies the commercial arrangements for the arming and operation and describes the mechanism for the administration of associated payments.
The payment terms for the commercial intertrip service are determined bilaterally between us and the generator.
Payments are made up of:
Arming payment (£/settlement period) – paid for each settlement period where the generator (at National Energy System Operator's request) allows signals to pass from the intertripping scheme to the relevant circuit breaker; and
Tripping fee (£/unit/trip) – paid when a signal is sent to the relevant circuit breaker of a generator causing the generator to cease output to the transmission system.
If an intertripping scheme is installed by a generator, we may also offer a capability payment (£/settlement period) – paid for each settlement period in which the scheme is declared available. This payment might typically be structured to recover any associated installation, maintenance and training cost.