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Degradation of composite insulators at material interfaces

Bastidas Erazo, Pablo Daniel

[Thesis]. Manchester, UK: The University of Manchester; 2018.

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Abstract

High-voltage (HV) outdoor composite insulators used in transmission lines are made of two polymers, comprising the core and housing, bonded together with metallic end-connections. The interface between these polymers is parallel to the electric field, which makes the insulators more prone to interfacial problems at these common points [1]. If interfacial ageing occurs, degradation and catastrophic breakdown can result [2]. Therefore, the design reliability of outdoor composite insulators depends on the high-strength bond between the core and the housing [3],[4]. Research findings by Kutil and Froshlic [5] indicate that delaminated areas, cavities and/or micro cracks in the medium are enough to initiate streamer discharges along the interface that are capable of degrading both insulating materials. The heat, UV radiation, and high-energy electrons produced from such discharge activity resulted in the growth of carbon paths along the interface, known as ‘tracking’, ultimately causing failure [6]. This investigation focuses on the development of tracking between silicone rubber and epoxy resin, with a view to replicating the tracking phenomena seen within composite insulators in service. A fine wire is placed between the dielectrics materials to enhance the local electric field magnitude and initiate discharge processes. The resulting partial discharge (PD) activity has been monitored. This Information has been used to understand the inception and propagation of the interfacial tracking. A strong relationship was found between maximum PD magnitude and track length. PD patterns and unique detailed images of the interfacial tracking development, allowed identification of the growth characteristics of interfacial channels and phases of tracking growth. Furthermore, a correlation in the mechanisms of interfacial degradation was found between the lab-fabricated samples and commercial composite rods. Finally, a growth model of interfacial ageing has been developed with the information from FEA models, PD patterns and the detailed images of tracking growth. The physical structure and chemical analysis of interfacial tracking is also disclosed to provide an insight into interfacial ageing mechanisms that occur in the composite insulators under electrical stress.

Bibliographic metadata

Type of resource:
Content type:
Administered thesis
Form of thesis:
Traditional
Type of submission:
Doctoral level ETD - final
Thesis title:
Degradation of composite insulators at material interfaces
Degree type:
Doctor of Philosophy
Degree programme:
PhD Electrical & Electronic Engineering (42 month)
Publication date:
2018-08-14T22:59:32
Institution:
The University of Manchester
Location:
Manchester, UK
Total pages:
268
Abstract:
High-voltage (HV) outdoor composite insulators used in transmission lines are made of two polymers, comprising the core and housing, bonded together with metallic end-connections. The interface between these polymers is parallel to the electric field, which makes the insulators more prone to interfacial problems at these common points [1]. If interfacial ageing occurs, degradation and catastrophic breakdown can result [2]. Therefore, the design reliability of outdoor composite insulators depends on the high-strength bond between the core and the housing [3],[4]. Research findings by Kutil and Froshlic [5] indicate that delaminated areas, cavities and/or micro cracks in the medium are enough to initiate streamer discharges along the interface that are capable of degrading both insulating materials. The heat, UV radiation, and high-energy electrons produced from such discharge activity resulted in the growth of carbon paths along the interface, known as ‘tracking’, ultimately causing failure [6]. This investigation focuses on the development of tracking between silicone rubber and epoxy resin, with a view to replicating the tracking phenomena seen within composite insulators in service. A fine wire is placed between the dielectrics materials to enhance the local electric field magnitude and initiate discharge processes. The resulting partial discharge (PD) activity has been monitored. This Information has been used to understand the inception and propagation of the interfacial tracking. A strong relationship was found between maximum PD magnitude and track length. PD patterns and unique detailed images of the interfacial tracking development, allowed identification of the growth characteristics of interfacial channels and phases of tracking growth. Furthermore, a correlation in the mechanisms of interfacial degradation was found between the lab-fabricated samples and commercial composite rods. Finally, a growth model of interfacial ageing has been developed with the information from FEA models, PD patterns and the detailed images of tracking growth. The physical structure and chemical analysis of interfacial tracking is also disclosed to provide an insight into interfacial ageing mechanisms that occur in the composite insulators under electrical stress.
Additional digital content not deposited electronically:
N/A
Non-digital content not deposited electronically:
N/A
Keyword(s):
Thesis main supervisor(s):
Thesis co-supervisor(s):
Funder(s):
Degree grantor:
Language:
en

Record metadata

Manchester eScholar ID:
uk-ac-man-scw:315542
Created by:
Bastidas Erazo, Pablo Daniel
Created:
14th August, 2018, 21:59:32
Last modified by:
Bastidas Erazo, Pablo Daniel
Last modified:
13th September, 2018, 13:51:21

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