Introduction: Live Line working was initially introduced in the 1960s and actively utilised in the 1990s on the Overhead Lines (OHL). The project will enable National Grid use to use innovative techniques to deliver benefits to the system operator. These benefits are primarily around minimising system outages to carry out work and reducing system operator costs. The transmission system is likely to become increasingly constrained over the next 5-10 years, based on forecast constraint costs, new access arrangements, continued asset investment requirements and new generation connections. Live Working in substations offers significant opportunities in enabling certain maintenance and defect work to be carried out against this background, however to provide assurance that the long term investment and commitment is workable on the existing network, a more in depth assessment of the substations is required in order to establish the criteria for live working can be met. This assessment would be undertaken by the French Electricity Company RTE who are one of the worlds experts on live working at High Voltage (HV).

The re-establishment of Live Line Working on OHLs within National Grid has already been approved by governance groups within National Grid and discussions with Ofgem on this matter have already taken place. Substation live working is the next logical step to undertake.

Historically the HV equipment maintenance work in substations has been undertaken on circuits which have been de-energised, isolated and earthed. This requires longer return to service times of circuits and limited access availability. Because of the way the network is being developed and enhanced to facilitate the build of new generation and asset replacement etc it will become increasingly more constrained and hence even more difficult to get system access for essential maintenance and defect repairs.

To fully undertake live working in substations, further investment in staff training and specialist equipment is required and hence, to justify this investment, the existing substations will need to be assessed to see if the configurations used will be compatible with the established criteria for live working.

Objectives: The project will monitor the feasibility of live substation working in support of improved, more efficient system access in critical system areas.