In collaboration with:
Cables in general form a large part of the regulated assets and as such network owners need to know more about the condition of these assets. Due to the nature of cables, it is very difficult to determine the condition without intrusive works, which are expensive and disruptive. Therefore, the observability of cables is currently low and maintenance strategies are more reactive than proactive.
Project objective
This project has investigated a range of data sources and outlines a cable health assessment framework to help DNOs estimate remaining useful life and health assessments. Additionally, this project provides suggestions on how to develop an end life prediction model for cables considering the RIIO-ED2 price control period. The main area of concern is the potential for increased load due to further utilisation of Low Carbon Technologies (LCT) via technologies such as Electric Vehicles (EVs), heat pumps, hydrogen and Distributed Generation (DG).
Delivery & Outcomes
The project considered past projects in this area to understand what work has been completed to date. The main objective of this phase of work was to define the follow on work packages for technical board approval (via a stage gate).
The second work package considered the development of a framework to support the health assessment of cables. Within this seven alternative techniques were identified based on a ratings matrix approach with emphasis placed on the practicalities of adopting the technique and the value of the data produced. The most appropriate techniques identified were: online PD measurements, functionality testing, general visual checks, conductor resistance testing, earth resistance and temperature measurements.
In the third work package the impact of adopting the proposed framework was investigated. This considered the time and effort in gathering data and the analysis opportunities of the potential data sets. The project identified possible applications for low cost cloud based monitoring solutions and alternative online monitoring equipment.
The fourth work package considered the remaining useful life and failure rate for cables between 2020 and 2028 when considering growth trends for LCTs. Within this work package two cable topologies with representative network scenarios were investigated. In order to investigate the impact of the LCTs on cable lifetime, a thermal model was constructed whereby the applied load could be related to the cable lifetime estimation. The hypothesis of cable aging is based on the Arrhenius Inverse Power Model (IPM). The model must be constructed for the cable sample under investigation but essentially employs a cross-sectional view of the cable sample. Over the 8 year investigation period the load increases due the worst case scenario were projected to reduce lifetime by 22 years at distribution level and 11 years for the mains cable. Based on the method employed the worst case failure rate levels were projected to increase by 18.5% on the distribution cable and 24% on the mains cable.
Impact
The improvement/development of data gathering techniques related to the health assessment or end of life assessment of cable systems. DNO partners need techniques that are streamlined to minimise system downtime whilst at the same time gleaning valuable data from the electrical performance from the cable assets at that point in time. This may involve the development of new novel techniques or the refinement of existing techniques (insulation resistance) to be more cost effective, streamlined and less time sensitive to perform in a field based environment. Ultimately, the availability of techniques that meet these requirements will improve the availability of data on cable assets longer term. The availability of data will be critical in the future for uncertain/changing load conditions.
The development of modelling tools to support the decision process for asset managers for the end of life assessment of cable systems. The follow on work would consider the development of the IPM model for key cables of interest and consider time based loading on a number of key cable scenarios. The ultimate aim will be to provide a tool to support asset managers in the end of life assessment of cables and accessories. We anticipate that issues/challenges with the cable system will first be apparent at mains/service level but are open to investigating cables at higher voltage. The change in use of the network will be a key factor to ensure that impact on asset life can be modelled/accounted for before issues become apparent in the field.
Next steps
The field based measurements (work package 2 and 3) could be expanded to yield further and valuable data sets for DNO partners. Follow on work could consider the application of these techniques at PNDC or in field based measurements. There is also the option of exploring the potential of currently available data sets. This would be the use of data such as maintenance records to support the end of life assessment of cable systems and drive further value from what is currently being recorded by DNO partners.
The modelling completed in work package 4 can be expanded to cover more cables of concern for DNO partners. The objective would be to develop a tool for asset managers to assess the impact of increased/alternative loading on key cables topologies of interest.
Get in touch
PNDC project lead: Eddie Corr .
For further information on this case study or to discuss collaborative opportunities, please get in touch.
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