This project investigates the methodology required to develop Underground Cable Health Index Tool to enable better decision making on whether to replace or maintain underground cables.
Underground cables in the distribution network system offer improved security of supply compared to overhead line systems. However a large portion of underground solid HV cables are nearing the end of their useful life which may require significant investments in order to maintain system reliability. UK Power Networks run approximately 44,422km of HV underground solid cables within its three licence area. This equates to approximately 28% of national population of HV underground cables.
There are various factors that may have an impact on the life expectancy of underground cables. These factors are related to thermal, electrical and mechanical issues which need to be identified. A proactive and methodical approach is required for prioritising investment on the basis of worst performing circuits. In order to achieve this it is vital to understand the condition of HV underground cables and to develop a HV cable prioritisation model. This project will develop a HV Undergound Cable health tool to give a rating to cables for their replacement at the right time before it fails.
The project will collect a number of HV cable samples from the field following a cable failure due to deterioration for forensic analysis. A one-meter cable sample half of which is faulty and half in good health will be collected from the field following a fault. Condition assessment will be carried out on these samples through forensic analysis in order to understand degradation mechanism of the cable and condition of cable sheath. Historic fault data will be reviewed for all the HV underground cables within UK Power Networks and asset information (including cable type, year of manufacturer, manufacturer, location etc.) will be collated from various UK Power Networks systems for analysis
A HV cable prioritisation tool will be developed based on the above information and a methodology to give a health index score to HV solid cables for their maintaince and replacement before their failure.
Currently, within GB DNOs, the current practice of maintaining HV faults is reactive as there is no mechanism in place to understand the condition of HV solid cables for their reactive replacements before failure. This project will understand cable deterioration mechanism and will develop a methodology to rank HV solid cables and replace them before their failure to improve network reliability. This is an innovative approach which has not been trialled before.
The project aims to learn the degradation mechanism of HV solid cables within DNO network to develop a strategy for HV solid cable replacements. An improved understanding of HV solid cables and their deterioration mechanism. This will allow to prioritise high risk underground HV cables for intervention before the occurance of fault.