Optical Instrument Transformers Research Articles

HVDC pollution testing of insulation: experience from service, laboratory and test station

The need for testing at HVDC and UHVDC levels has increased dramatically over the last few years. Typically test objects include valves, cables, line insulators, cable accessories, optical instrument transformers and station post insulators. Some of these tests are dielectric tests and in many cases the tests include also pollution testing, which is a main dimensioning parameter for outdoor insulation in DC. This publication focuses on the experience that STRI has gained throughout years of investigating and testing insulators under HVDC in polluted conditions. Examples from service and field stations and laboratory investigations of artificially and naturally polluted ceramic and polymeric insulators are presented. Examples of practical implementation of laboratory results in design practice are also given.

Development of an optical instrument transformer for DC voltage measurement

This paper deals with the principles, design, assembly, testing results and practical application of a new type of optical voltage instrument transformer based on the Pockels effect, developed for the measurement of DC voltage, with a view to the protection and control of DC power transmission systems including frequency changer power equipment. In order to develop more accurate devices, the authors conceived a new scheme capable of overcoming the particular problems of DC voltage measurement which cause measurement errors. In this scheme, the DC voltage to be measured is chopped and applied to the Pockels crystal. An optical DC voltage instrument transformer was developed and tested using this scheme. The results of the factory tests showed that the characteristics of the new device conform with the required specifications of DC voltage instrument transformers for the protection and control of frequency changer power equipment. The results of field tests conducted for 1 year at an operating frequency conversion substation confirmed that the device is of adequate reliability. >

Development of optical instrument transformers

The authors describe the design(, assembly(, and testing results for prototypes of an optical current transformer (CT) and a voltage-dividing-type voltage transformer (PD). The optical CT and PD were developed to be applicable to three-phase enclosed-type 300 kV gas-insulated switchgear (GIS) and air-insulated 168 kV substation systems. Test results for the newly developed optical CT and PD showed that their basic properties conform with JEC 1201, the Japanese standard for electric-power instrument transformers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>