C57.13.3-1983 - IEEE Guide for the Grounding of Instrument Transformer Secondary Circuits and Cases
Description: The primary emphasis of this guide is personnel safety and proper performance of relays at powerline frequencies. Historically, it has been common practice in the US to connect some part of the secondary circuit of voltage and current transformers to the station ground system. The present preferred practice is to locate this safety ground with suitable ground isolation test facilities at the first point of application (switchboard or relay panel) of the instrument transformer secondary circuit. The circuit ground isolation facilities will permit convenient testing of circuit insulation to ground. Previous publications have made significant contributions to consistency in some areas of grounding practices. The guide will include those contributions that are generally practiced today, make revisions where present experience and practice indicate them to be desirable, and make recommendations in new areas of interest not previously addressed. Diagrams are included to illustrate the recommendations.