The results from these projects are delivered in ways that can easily be applied to improve system performance while managing costs. Many results can be applied immediately while other research may yield benefits over a longer time frame. This approach is expected to offer UK Power Networks and the GB consumer both short- and long-term value. Specific research activities include:
· Development of component specific information to assist in the selection, application and inspection processes;
· Assessment the effectiveness of inspection tools;
· Development of maintenance, inspection and assessment guidelines;
· Reference books, guidelines, and technology transfer workshops and
· Collaborative environments for sharing lessons learned and best practices.
Objectives
To further knowledge, guidance and gather tools in managing overhead transmission lines (P35) and efficient lifecycle management of electrical assets (P37).
Learnings
Outcomes
Below are the accomplishments and deliverables with associated report links produced in 2021/22 and 2022/23:
P35.002 – Conductor, Shield Wire and Hardware Corrosion Management
In 2020, the geometry factor for 17 conductor types were completed for service life modelling using the atmospheric corrosivity maps. Conductor movement has been identified as the cause of the most severe type of conductor corrosion. In 2021, the team correlated vibration sensor data and weather data to categorize severity levels of fretting corrosion and development of field repair methods. An understanding of the corrosion initiation mechanism in AAAC and Alumoweld conductors was developed. Deliverables produced in 2021/22 include:
• Corrosion Management Reference Book
• Conductor Corrosion Management Guidelines
• Vibration-Induced Corrosion and Its Subsets
Deliverables produced in 2022/23 were:
• Corrosion Management Reference Book
• Guidelines For Evaluation of Conductor Failures Due to Corrosion
• Impact of Vibration on Conductor Corrosion and Degradation
P35.003 – Structure and Sub-Grade Corrosion Management
During 2020, reference guides were published on Wood Pole Management and Concrete Management. The resolution of the soil corrosivity maps have been increased and metrics were developed for stray and circulating current corrosion. In 2021/22, field validation and refinement of stray current corrosion metrics and an evaluation of the effects of AC circulating currents coupled with DC stray currents was developed. Evaluation of engineered backfills was added to the concrete management reference guide. Deliverables produced in 2021/22 include:
· Corrosion Management Reference Book: Chapters 1, 2 and 3
· Fleet Management Environmental Model Development
· Electric Structure Corrosion due to Pipelines, Subways and Other Commercial Activities
Deliverables produced in 2022/23 plans were:
• Quick Break Whips: Continued Testing – Technical Update
• Practical Maintenance Guide Additions – Technical Update
35.005 – Composite Structure Management
During 2020, the knowledge of composite material mechanical performance when operating under temperature extremes, and after exposure to wildfire conditions increased. The team tested lightning and switching impulse flashover distances for typical 230 kV composite structures. During 2021/22, a performance evaluation of composite structure attachment hardware was performed. Development of composite structures application guide. Increase knowledge of HV impulse performance, and effect of puncture testing on wet pole composite material. Deliverables produced in 2021/22 include:
· Evaluation of Attachment Strengths of Composite Structure Hardware Report:
· Comparison of Ultimate Strength of Aged vs New Composite Poles
· Composite Structure Application Guide
Deliverables produced in 2022/23 plans were:
• Effect of wildfire temperatures on composite structure properties
• Accelerated aging of composite poles – full scale testing to failure
• Composite structure performance – pole and crossarm hardware testing
P37.102 – Circuit Breaker Life Management
During 2020, SF6 leak sealing technique development continued to advance through full scale laboratory tests and utility field trials. The EPRI Circuit Breaker Guidebook was enhanced. A test plan was developed to evaluate online circuit breaker monitors.
Research in 2021/22 focused on advancing SF6 leak sealing, evaluation of online circuit breaker monitors and developing interactive guides to assist field personnel in troubleshooting circuit breakers. Deliverables produced in 2021/22 include:
• Novel SF6 Leak-Sealing Techniques reports
• Effectiveness Assessment of Circuit Breaker Online Monitoring and Diagnostic Testing
• Circuit Breaker Reference Guide
• Circuit Breaker Maintenance Field Guides
• Circuit Breaker Mechanism Maintenance Guides
• Circuit Breaker Troubleshooting and Corrective Maintenance Guidance
Deliverables produced in 2022/23 were:
• Circuit Breaker Reference Guide Update
• Circuit Breaker Contact Condition Assessment – Dynamic Resistance Measurement
• Circuit Breaker & Maintenance Guide – Update
• Circuit Breaker Monitoring Algorithms – Update
• Develop innovation algorithms for Dielectric Condition Assessment – Update
• The planned SF6 Leak Sealing Field Trial at UK Power Networks has not taken place due to the impossibility of finding a suitable l site location among investigated UKPN substations.
P37.108 – Gas Insulated Substations and Lines
SF6 replacements is the first of the two important tasks in the project. During 2020, EPRI performed HV tests and tracking and reporting on SF6 replacement deployments worldwide. The second topic is GIS/GIL diagnostics using the newly commissioned GIS laboratory in Charlotte, NC, USA to generate valuable insights.
During 2021/22, High Voltage testing of SF6 replacements continued at differing pressures and mixtures. The EPRI GIS laboratory in Charlotte (United States) will have defects intentionally introduced to evaluate a wide range of diagnostic techniques. Deliverables produced in 2021/22 include:
• SF6 Alternatives for GIS/GIL: Laboratory testing and worldwide experience report
• Technical Webinars on SF6 Alternatives, GIS and GIL
• SF6 Computer-Based Training Modules
Deliverables produced in 2022/23 were:
• SF6 Alternatives for GIS/GIL: Design additional tests and share lessons at workshops/conferences
• SF6 Computer-Based Training Modules – Update
• Advance GIS/GIL Testing and Diagnostics – Laboratory Investigation and Update
• GIS/GIL Decision Framework – Literature Search, Update Video Publication
P37.113 – Bushing Monitoring & Diagnostics
Before 2021, three polymer bushings in the 138 kV yard had been energised for almost two years with various voltages, over voltages, currents, and extreme weather conditions. The bushings have been monitored with off-line testing and on-line bushing monitoring system. To better assist utilities on specifying polymer bushings, a polymer bushing guide has been initiated in 2020.
In 2021/22, the polymer bushings in the 138 kV yard continued to be subjected to harsh electrical and environment conditions. The bushings were subjected to impulse testing. To understand the most common failure modes of polymer bushings, a study was performed. Accelerated bushing testing to replicate the common failure modes was designed. Deliverables produced in 2021/22 include:
• Performance of polymer bushings under extreme environmental and loading conditions
• Guidelines on specification, maintenance of polymer bushings
• Analysis of worldwide reliability and performance experience of polymer bushings
Deliverables produced in 2022/23 were:
• Develop Bushing Failure Guide – Collect Performance/Failure Data and Update
• Bushing Forensic Studies – Update with latest investigative results
• Performance of dry type bushings under extreme environmental conditions – Design test, evaluate product/technology and update with latest investigative results
• Develop Bushing Reference Guide – Literature Search, update with investigative results and update reference guide
• Develop Radio Frequency Acoustic Emission Sensor – Design test and conduct field test.
• Bushing Diagnostic Test Effectiveness Assessment – Design test, assess product/technology effectiveness and update with latest investigative results
The following dissemination activities took place during the project duration:
Several meetings with EPRI held virtually due to COVID-19 (2021-2022)
Physical meeting: EPRI Spring Task Force Meeting, Charlotte, North Carolina, United States, March 2022
Lessons Learnt
The planned SF6 Leak Sealing Field Trial at UK Power Networks has not taken place due to the inability to identify a suitable location. When planning similar future trials, it is important to know that suitable leaks have to be located at a Ground potential equipment- that can be easily accessed, and leak needs to be quite evident.
