IEEE C57.13.1-1981

In the application of protective relays, the most widely used input quantity is current. A multiplicity of different protective relays either utilizes current directly, combines it with other currents as in differential schemes, or combines it with voltage to make impedance or power measurements. The source of relay input current is from current transformers which may be located on the bushings of power circuit breakers and power transformers, on the bus bars of metal clad switchgear, or installed as separate items of equipment located as required.

The purpose of this guide is to describe field test methods that will assure that the current transformers are connected properly, are of marked ratio and polarity, and are in condition to perform as designed both initially and after a period of service

New IEEE Standard - Superseded. A description is given of field-test methods that will ensure that the current transformers used as a source of relay input current are connected properly, are of marked ratio and polarity, and are in condition to perform as designed both initially and after a period of service. The standard covers safety considerations; current transformer types and construction and the effect of these on test methods; insulation resistance tests; ratio tests; polarity check; winding and lead resistance (internal resistance); excitation tests; burden measurements; and specialized situations.