Fault passage indicators (FPIs) are used as a means of identifying the faulted section of network in long and branched distribution network overhead lines or interconnected cable circuits. This is a vital enabling technology for automated fault isolation and restoration, minimising the disruption of customers’ supplied following faults. Testing FPIs at the PNDC helps distribution network operators (DNOs) make informed decisions when deploying these devices on their network.


  • Share key learning outcomes in the form of best practices when installing FPIs, configuring them and interpreting their indications.
  • Understand the network operating conditions or external factors (e.g. electromagnetic field interference) that may adversely impact the performance of the FPIs or their indication reliability.


A complementary set of network and laboratory tests were performed to reflect realistic operating conditions the FPIs will be subjected to. The PNDC high voltage (HV) fault thrower was heavily utilised during testing, while fault current measurements and FPI indications were recorded to evaluate the FPI performance under these conditions.


Empirical evaluation of the performance of commercially available FPIs under varied fault, network operation and installation conditions. The performance data obtained enables an improved understanding of FPI reliability and how their indications should be integrated into network automation and post-fault recovery schemes.

  • Comprehensive performance evaluation of different FPI technologies
  • Identification of communications related issues associated with FPI indications
  • Learning outcomes delivered to DNO IFI (innovation funding incentive) projects


  • 3 Fault Passage Indicators evaluated
  • 50 HV faults thrown
  • 450A Typical fault current
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Case Studies