There is a need to utilise High Temperature Low Sag (HTLS) conductors within our network as it increases the capacity of overhead line (OHL) conductors with no need for further reinforcement. Due to the composite nature of the core of HTLS conductors, traditional non-invasive inspection methods are not applicable and there is currently no method to inspect or monitor the condition of the conductor post installation. The proposed solution is to use guided wave inspection, by means of a prototype device, which works through a single transmitter/receiver where an energy wave reflection is analysed to detect defects. The prototype device will be demonstrated and aims to provide a definitive answer as to whether the inspection methodology is applicable to HTLS conductors.
Benefits
The potential benefits identified are listed below.
• Offers a non-intrusive means of assessing the condition of the existing carbon cored, HTLS conductor on the Transmission network. A capability that is not known to exist within the UK or globally.
• Improve estimates on the end-of-life of conductors and the ability to assess the level of damage to the conductor following incidents, such as tree strike. This could reduce repair time and avoid unnecessary repair work.
• Enables the future use of carbon cored, HTLS conductors on the transmission system due to addressing the current concern that these conductors cannot be assessed.
• Carbon cored conductors have been installed in over sixty countries in over 1,100 different projects. With no current diagnostic tool on the market, there would be high potential for commercialisation/licence of the tool.
• If testing is successful, the new method will reduce lengthy outages following unplanned disruptive events and full section replacement costs as conductors will be non-destructively inspected and repaired, if needed, rather than replaced.
• Less conductor replacements could also reduce their environmental impact by minimising manufacturing and procurement of new conductors as well as mobilisation of equipment and staff required for their replacement.
• Developing this prototype will enable learnings to be shared so all HTLS conductors can benefit from this innovation.
Note, to achieve the above benefits a second project would be required to convert the lab-based prototype into a conductor mounted field unit.
Cost-Benefit Analysis (CBA)
Assumptions
Our CBA model and methodology was used to estimate the benefit value of this project. The model is based on the following assumptions:
• The operational cost (OPEX) was distributed over 45 years, which is the standard transmission asset life, to mitigate cost fluctuations.
• Annualised the capital expenditure (CAPEX) because of the uncertainty around the timings of conductor replacements during their lifetime.
• All values are expressed in 2018 real as per previous Ofgem models’ base year.
• Planned maintenance cost was assumed to be one third of the cost of unplanned outages. Both the costs of outages and minor conductors’ replacements were factored in to cover any issues identified during planned inspection.
• Assumed the device cost for commercial stage is £3960 (discounted by 10%) and used this to estimate the scaled benefit.
• The successful device development involves three stages: lab testing (current stage), demo (live SSENT site testing), and wider deployment to our network (60 km scaled benefit analysed). The lab testing is planned to be carried out at an 8m - 12m conductor to improve knowledge on the design, so no financial benefits are expected at this stage.
• Assumed the cost of the demonstration on live SSENT site testing is twice that of the lab testing, factoring in resourcing, contingency and a 50% probability of success. This is a highly conservative approach to reflect as the benefit value estimated considers all the development risks from prototype until final deployment.
• Assumed the efficiency of the device is 70%, potentially reducing 70% of unplanned issues.
Results
This analysis focuses on the assessment of the scaled benefits of EMAT transmitter device (60km conductor length).
• If the lab testing is successful, further demonstration will be required to validate the outcomes. The innovation will be tested in a live SSENT site to assess its capabilities. The scaled benefit of this project was estimated to approximately £280k over lifetime.
• However, due to the low TRL and high uncertainty, a risk assessment was conducted to account for the potential costs and risks of applying this technology to the eligible part of our network. The minimum risk-adjusted scaled benefits estimated to £91k over lifetime (approximately £1,530 per km).
• The Benefit-Cost ratio (BCR) was estimated then to 3.6, which means that for every £1 of project development spend, this innovation has the potential to return £3.6 by the end of the asset lifetime.
The scaled benefit will be revised once (and if) this project is successful at the demonstration testing and before progressing to the next stage of deployment.
Sensitivity analysis:
• Due to the high uncertainty of the device's efficiency, a sensitivity analysis was carried out assessing its impact on the potential scaled benefits. The minimum efficiency level of the device is 34% for this project to be considered as viable.
• The inspection duration and frequency have high impact on the potential benefits of this project. It is assumed that the conductors will be inspected once every 7 years, as such, the estimated benefit values reduced by 23%. If inspection lasts 2 days every 7 years, the project still results in financial benefits, but the benefit value will be reduced significantly by 91%.
Key Risks:
• The project requires further development to be used widely to inspect conductors in the whole SSEN Transmission Network.
• Due to the unknown period of time from development until becoming BAU, the costs of producing an actual final device could increase or be adversely affected by any future market fluctuations.
