Respond trials

Respond trials

Respond’s Fault Level Assessment Tool assesses fault level in near real time and enables or disables one of three fault level mitigation techniques.

Adaptive Protection

Also known as sequential tripping, this technique re-sequences the operation of circuit breakers and is retrofitted into existing substation equipment.

As part of the Respond trials Adaptive Protection is installed at five 11kV or 6.6kV high voltage (HV) substations and two 33kV extra high voltage (EHV) substations.


This current-limiting fuse detects the rapid rise in current when a fault occurs and responds within 1/200th of a second to break the current. The IS-limiter is an existing technology used on private networks in Great Britain and extensively on public networks in Europe, USA and Australia as a fault current mitigation technique.

This will be the first installation of an IS-limiter on a distribution network in Great Britain. As part of the Respond project we are aiming to demonstrate how these devices can be deployed safely and legally and unlock the benefits this technology can provide for customers.

IS-limiters are installed at two high voltage substations. Outram fault level monitors are installed at seven sites to validate our network model and the Fault Level Assessment Tool.

During the project trials we need to validate every fault that occurs and ensure that the Respond installations have operated correctly. The map below shows where the various technologies are installed on our network and the number of times the technology has operated after a fault.

Reports on each of the faults that have occurred can be found on the 'Respond trials key documents' page of our website.

Respond trial sites

Map showing locations of respond trial sites

Fault Current Limiting service (FCL service)

This commercial solution provides a unique opportunity for industrial and commercial demand or generation customers to benefit from selling an FCL service to us through a managed service agreement.

When a fault occurs, all synchronous rotating equipment, from sources of generation and load connected to the electricity network, contribute to fault current. Using new technology, being trialled as part of the Respond project, a customer’s generator or motor can be turned off remotely for a few minutes, so that it no longer contributes to the fault current.

Before we could purchase FCL services, we carried out a customer survey with industrial and commercial (I&C) demand and generation customers.

Find out more about our customer engagement activities on the Respond customer engagement page.