Smart Cable Guard will trial a method of identifying faults by detecting the partial discharge, or PD (a momentary arc/spark). It will help our field staff find the fault faster and help restore power to our customers sooner. It also aims to pick up issues with the underground cables before they become permanent, thereby preventing power cuts to our customers.
This project is trialling the use of the smart cable guard (SCG) devices from DNV to detect faults on our underground network. We will be doing this by deploying 20 sets of SCG devices on 20 different sections of underground cables. SCG aims to detect and locates PD that occur because of weak spots in the cable insulation and joints. Weak spots in the cable generating PD are, in most cases, an indication of an eventual failure.
This project will be carried out in three phases:
Phase 1 – Site selection and survey. This phase involves selecting circuits to monitor and contacting DNVGL to confirm whether monitoring those circuits will be possible.
Phase 2 – Installation of the units. This phase will involve installing the units at the substations within the SPN network. This will be a combination of operational teams and DNVGL staff working together. During the installation, there will be training for UK Power Networks’ (UKPN) engineers regarding installing the equipment.
Phase 3 – Monitoring phase. This phase will be carried out over 18 months. This will see DNVGL monitor the outputs of the units in conjunction with UKPN asset engineers to establish where weak points are. When weak points are identified, a decision may be made whether to actively repair the circuit or not. If it is chosen to proactively act, then operational staff will proactively highlight the weak spots and send samples for forensic analysis.
At present UKPN are observing 1,400 underground high voltage HV (HV) cable failures per year across 45,000 km of HV cables. This requires large expenditure on unscheduled repairs. There is currently no solution in the UK that allows online monitoring of Partial Discharge (PD) of HV cables and locating a fault or incipient faults further than the first leg of the feeder. There are several solutions which look at PD from the primary substation. However, these only measure the first leg out of a feeder, and they also require a further location to find the exact location of the fault or PD.
SCG may detect such PD activity or weak spots and pinpoint their location with an accuracy of 1% of the cable length being monitored by the system. This may be of great value to Distribution Network Operators (DNOs) in making the optimal financial decisions about the proactive repair and replacement work of cables at a reduced cost.
We would learn if this technology can be used on UKPN’s network and how it may be used to plan for repairs proactively. The project will entail trialling the equipment and testing its capability to identify weak spots and fault locations. Cable samples will then be taken from the weak spots and analysed. There will also be an element of leaving the weak spots on the network and seeing how the PD behaves between the time it is picked up to the point of failure.