scope:

Foreword 

(This Foreword is not a part of ANSI/IEEE C57.13.3-1983, IEEE Guide for the Grounding Instrument Transformer Secondary Circuits and Cases.)

The Guide for the Grounding of Instrument Transformer Secondary Circuits and Cases was originally published in March, 1951, as AIEE Application Guide No. 52. This original guide went out of print in 1976. The proposed new guide, ANSI/IEEE C57.13.3-1983, is intended to replace the original AIEE No. 52 and to update its content to include present practices. The primary emphasis of the new guide is personnel safety.

A number of diagrams have been included in the new guide to help illustrate recommended practices. The recommendations of the current National Electrical Code and the practices of various public utilities and manufacturers were taken into consideration. Hence, this guide recognizes the more commonly accepted practices and incorporates them into a general set of rules, with permissible exceptions.

This guide was prepared by the Grounding of Instrument Transformer Secondary Circuits and Cases Working Group of the Relaying Practices Subcommittee of the Power System Relaying Committee of the IEEE Power Engineering Society.

Scope 

This guide contains general and specific recommendations for grounding current and voltage transformer secondary circuits and cases of connected equipment. The practices recommended apply to all transformers of this type, including capacitive voltage transformers and linear couplers, irrespective of primary voltage or whether the primary windings are connected to, or are in, power circuits or are connected in the secondary circuits of other transformers as auxiliary cts or vts. Although most diagrams included in this guide show relaying applications, the recommended practices apply equally to metering and other areas where instrument transformers are used.

Exceptions to grounding are permissible or sometimes required where advantages obtained by not grounding, in certain instances or in certain types of installations, are considered to outweigh the safety or other advantages obtained by grounding. Such exceptions should comply with the recommendations of ANSI C1-1987 [1]¹, even though utilities are presently exempt from the requirements of this code.

¹The number in square brackets corresponds to that of the reference listed in 1.3 of this standard; bracketed numbers preceded by B correspond to Section 5, Bibliography.