Dry HV insulation

A dry type HV insulation system for extreme environments   Abstract The aim of this article is to make readers aware of a dry type,...

byRobert L. MIDDLETON and Eric EUVRARD


A dry type HV insulation system for extreme environments

 

Abstract

The aim of this article is to make readers aware of a dry type, paperless insulation technology that offers a safer and cost-effective alternative to traditional oil-filled current transformers. The design concepts and advantages of this unique HV dry type current transformer technology have been delivering verifiable improvements to the power grid over the past 20 years from 35 kV to 600 kV. The example of the implementation of this technology in Canada is a good case in point. Multiple evolutions of the technology have been continuously expanding its application from HV to UHV operation. Furthermore, the addition of a built-in insulation condition monitoring system completes the safety and sturdiness of the platform.

Keywords: Cascade construction, current transformer, dry type insulation, embedded monitoring, paperless

 

1 Introduction

The HV DryShield® current transformer, which uses no oil or gas and no paper, offers an upgraded safety and reliability solution for utilities faced with the need to replace end of life and/or failing oil-filled current transformers. This article discusses the advantages of this unique current transformer technology and its implementation into the grid. The later introduction of a smart HV dry type current transformer with its built-in real-time monitoring of its primary insulation condition and secondary accuracy errors is also discussed. This article then describes the design evolution of this technology into the cascade construction which offers significant cost savings and reliability benefits for EHV or UHV applications.

2 Development of this HV dry type insulation technology

A totally original dry insulation structure for current transformers using PTFE (PolyTetraFluoroEthylene) was developed in China throughout the 1980’s, patented in the 1990’s, and later trademarked as HV DryShield®. This technology has a proven service record with over 20,000 current transformers with ratings ranging from 35 kV – 600 kV in operation in all types of operating environments on T&D systems in many parts of the world [1]. This HV dry type current transformer uses a “U” shape primary and sealed, waterproof dry-type secondary windings, making it an immediately recognizable product in a substation.

 

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