Recent standardization developments and test-experiences in switching inductive load current

Abstract

In recent years, the demand for testing of inductive load current switching duties has significantly increased. Parallel to this, a range of changes to the IEC standard 62271-110 have become effective. This contribution is intended to give an overview on some recent test experiences in inductive load switching with circuit breakers in a voltage range 12–550 kV, showing practical examples, changes and interpretations of the latest IEC standard. In the first part, an introduction will be given on the inductive switching duty, its typical features and its standard, IEC 62271-110. In the second part, vacuum circuit breakers are considered. Compared to SF6 circuit breakers, the re-ignition pattern differs significantly, given the inherent capability of vacuum circuit breakers to interrupt high-frequency current. This was identified by CIGRE WG A3.27 on high-voltage vacuum circuit breakers. Test-examples of vacuum breakers up to 84 kV regarding shunt-reactor switching are shown and explained in its Technical Brochure 589from 2014. Also, test-examples of HV motor switching, and the inherent overvoltages due to multiple reignition and virtual current chopping are highlighted and explained quantitatively. In the third part, shunt reactor switching with EHV circuit breakers is considered. Test examples will be highlighted of 550 kV circuit breakers. Recent publications have shown that more and more air-core shunt reactors are applied at EHV level. It will be demonstrated that in such cases, TRV requirements, in excess of those, as specified in the IEC standard may be met.