Connection outage scheduling

What are connection outages, and how are they scheduled?

As the Transmission Owner for England and Wales, we are key to connecting a variety of assets to the high voltage network. Before a customer is ready to connect, certain processes must be followed to ensure the safe operation of the network and surrounding equipment.

Asset Health
Circuit breaker detail

Significant work, such as a new connection- requires outages to be scheduled. This might mean taking individual assets and/or circuits offline.  The outages are part of ensuring critical 'Safety from the System', as without an outage, engineers cannot commence connection works.

How are outages planned?

Outages are planned with full utilisation of resource in mind and scheduled to preserve network resilience. The work required to deliver a new connection is complex and there are a variety of tasks that must be completed.

First, the Connection Engineer from National Grid Electricity Transmission (NGET) will request the new outage date which is assessed by System Access within Network Development and the Electricity System Operator (ESO). These outages are scheduled up to 6 years in advance and are subject to operational assessments whilst liaising with the ESO, in conjunction with projected demand requirements to ensure the system balance can be maintained. This approval is conditional, and its confirmation depends on the planning in the Year Ahead process, when the ESO will confirm the dates. Once this is complete, the outage is then managed actively as part of the Current Year plan. A planned outage may be impacted by factors like network faults, third party issues, weather, and other security of supply issues.

This careful scheduling means that punctual project delivery timescales are critical. Customer connection dates for prospective projects should be provided based on detailed system modelling studies and network planning requirements to ensure the network remains safe and reliable. These considerations include an assessment of other connections and other non-customer driven work.

Once an offer date has been given, and all necessary studies have been completed, preparations will begin to build the connection. Key equipment is ordered, contractors are booked, and outage requirements are confirmed. Works are planned to avoid conflicts of resource and to ensure minimal impact on the operational networks.

New shunt reactor placement

Outages secured for connections can also have a dual purpose. Whilst a particular asset is offline, NGET can ensure the most efficient use of resources to both deliver the necessary connection works, but also to deliver important maintenance and refurbishment. This helps to ensure the system is reliable, effective, and safe.

Once the outage has been scheduled, changes are challenging to make. Since resources are so carefully aligned, and system access must be agreed in conjunction with network security requirements, outage dates should be adhered to wherever possible. If the request is urgent and cannot be avoided, at least 12 weeks’ notice must be provided to the responsible NGET parties. However, this will often have other impacts on project delivery timelines, or other connection works. This enables our teams to account for other impacts, whilst working with the ESO to ensure the system security can be maintained. This amount of notice is required for all types of outages, to ensure our teams can conduct their work safely and securely, whilst ensuring security of supply for the end consumer.

Our future network strategies consider all present and future connections to ensure that the network will be as efficient and reliable as it can possibly be- whilst moving towards net zero. These strategies are modelled on the expected network conditions at a given date, and future projects can be scoped accordingly. Our long-term plans rely on consistent and effective delivery of current projects in the pipeline to ensure the accuracy of future plans, and to ensure new customer connection points can be planned in the network.