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Embedded Distributed Generation Electronic Fault Current Limiting interrupter

Funding mechanismNetwork Innovation Allowance
DurationSep 2018 - Mar 2022
Estimated expenditure£3.016M
Research areaNew Technologies and Commercial Evolution
  • South West
  • South Wales
  • West Midlands
  • East Midlands
  • September 2021

    The project team’s ongoing work through this phase of the project is to understand and record the performance of the device in the field. Unfortunately, the …


  • Design an 11kV FCLi for a <=5MW generator.
  • Manufacture the FCLi.
  • Perform detailed testing on the manufactured FCLi including Factory Acceptance Testing, external lab testing and ‘soak’ testing.
  • Complete Internal Arc Testing of a prototype device.
  • Provide learning and recommendations for the suitability of such a device for implementation in the distribution network.


The ever increasing penetration of embedded generation coupled with recent improvements in network interconnectivity, have led to rising distribution network fault levels, close to the rated capability of existing equipment which pose several challenges to both DNOs and Independent Power Producers (IPPs). More specifically, new connections are made possible through conventional resource-intensive and often disruptive network reinforcement, with substantial cost and delays to the IPPs which can make these connections unviable. This leaves available generation capacity underutilised, inhibiting the further decarbonisation of the network. In order to enable a scalable and long term path for such connections, the fault current contribution from new generators needs to be reduced to near zero. While some generation sources contribute little fault current (inverter based generation like solar), synchronous ones (such as combined heat and power, CHP) contribute significant fault current.


The project aims to design and test a newly developed solid state Fault Current Limiting Interrupter (FCLi), that can limit the fault current contribution of distributed generators and therefore overcome fault level issues that can limit the network capacity and prevent future connections. The three phase FCLi will be designed for 11kV generator connections ≤5 MW and will be robustly tested to provide learning on the suitability of the technology for implementation in distribution networks. If the complete testing of the device is successful, it will then be trialled within WPD’s 11kV network.

The project is to be delivered collaboratively between WPD and UKPN to ensure that a device is developed to suitably be deployed throughout GB. The project scope is described in more detail below but will consist of collaborative working on the design of the FCLi device as well as factory and laboratory testing to ensure that it is suitable for longer-term testing and site trial.