HV faults on the underground network account for a large proportion of unplanned outages, where customers may remain off-supply until the fault is found and repaired unless an alternative network arrangement is used to back feed. To help solve this problem, HV Pinpoint aims to develop a methodology for detection and precise location of pre-fault events in the HV underground network. This solution may be used in conjunction with the Pre-Fix NIA project method to provide a more precise defect location, or as an alternative pre-fault method. The intention of this is to reduce the reliance on test van methods, as well as providing a new solution to more easily retrofit sensor on to existing underground cables.
Benefits
Reduction of fault management costs through:
- Reduced operational staff time spent during the restoration and location phase of the incident when compared to test van methods.
- Accurate, prompt, validated event location requires smaller excavations and surface restatements to find events
- A reduction of CIs/CMLs resulting in a reduction of IIS penalties incurred.
Improved customer service through:
- Proactive pre-fault management will reduce unplanned outages and customers can be adequately prepared and supported throughout necessary planned works
- A systematic reduction in network operation costs may ultimately be reflected in lower bills for customers.
Reducing our need for PD Mapping
An analysis of the potential financial benefits of using the method developed in this project as an alternative to Partial Discharge (PD) mapping was undertaken – this is mainly linked to operational cost savings.
To quantify this, an estimate for the amount of PD mapping required per year if Pre-Fix was rolled out across the business was derived. This was derived as both a lowball estimate and a highball estimate, to get an idea of the range of benefits this project could deliver.
- For the lower estimate, we have assumed that 376 circuit sections need to be PD mapped per year. This was estimated using data from Pre-Fix to suggest 6% have pre-fault activity.
- For the higher estimate, we have assumed that 1000 circuit sections will need to be PD mapped. This is based on historic fault data from 2021 to 2023.
The project will inform us on the equipment cost, and the operational savings when compared to PD mapping.
Learnings
Outcomes
As this project is still ongoing it would be too soon to provide comprehensive details of the project outcomes at this stage. These will be documented in the next annual progress report. Progress so far is described above.
Reports are being produced as the project proceeds and, so far, four have been completed as follows:
· Inception Report (May 2024)
· Report on detecting pecking events at typical depths with a “mat” of field sensors (September 2024)
· Report on tests on HV cable circuit with created events at Sundridge and related work (January 2025)
· Summary of work carried out during the proof-of-concept stage of the project, including the results from location validation testing (February 2025)
Further reports will be produced as the work of the project progresses.
Lessons Learnt
As the project is still ongoing learnings are still being generated. These will be documented in the next annual progress report. Nevertheless, a learnings log is being maintained, and this already contains items in respect of the tests undertaken at the UKPN Sundridge Training Centre in August and September 2024 and those done at the National Grid Deeside Innovation Centre in December 2024. These learnings included that:
· a broad range of live data could be collected using an updated Klikpower sensor, other equipment, and the Kestrel website but refinements were needed.
· pulse injection from the PETU pulse generator via the Klikpower sensor was demonstrated and pulses observed at other network locations.
· a proof-of-concept pulse injection and mobile reception system can be used to detect injected signals at a depth of 750mm or more for at least 300m along a cable using a simple battery powered injector pulsing at approximately 1Hz. The distance at any point along the route can be established by time of flight compared to a reference timing signal. The features and systems necessary to achieve the necessary measurement accuracy were identified.
· a proof-of-concept sensor mat system can detect fractional cycle type events of 50 Amperes when located 750mm above known event locations.
Further learnings relating to the sensor mat planned to be used for pinpointing events, issues resulting from the use of the HV Pinpoint approach with triplex cables, experience gained from installing KlikPower sensors and PETU’s on live networks, and other aspects of the project are expected to be documented.
As well as updated learnings the next annual report will also cover recommendations on next steps including what further development and trialling (if any) needs to be undertaken, what barriers need to be overcome, and how commercialisation of the approach can be pursued.
