Introduction: Distributed generation (DG) is a vital enabler of the low carbon transition. However, in urban networks, fault level constraints may hinder DG deployment. We will conduct two trials to demonstrate both the feasibility and possible applications of Fault Limiting Circuit Breakers (FLCBs) for releasing additional fault level headroom to enable more DG connections.

The decarbonisation of heat is a key element of the Government’s Carbon Plan. A key enabler of this decarbonisation is the growth of district heating and DG in the form of combined heat and power (CHP). However, fault level constraints are becoming a barrier to connecting new DG in urban areas. With plans for increased local generation, especially CHP, the already limited headroom in substations will be quickly exhausted. In one scenario, London will see a greater than six-fold increase in connecting CHP by 2031, with 73% of LPN substations requiring fault-level reinforcement. Traditional reinforcement as a connection solution will make new DG financially unattractive to customers.

Objectives: The result of the trials will be that two new technology applications to address fault levels will be proven on a live network, accelerating the development of these devices towards being an option for customers and DNOs in the near and medium term. The learning disseminated will provide existing and new DG customers clear information of the options available to connect more quickly and cheaply than before.