Described in this guide are protective relay applications involving electric service to consumers that requires a transformation between the utility’s supply voltage and the consumer’s utilization voltage. It describes the factors that need to be considered in the design of adequate protection facilities, outlines modern relay practices, and provides several examples of the protection of typical utility-consumer interconnections.

This guide contains information on a number of different protective relaying practices for the utility-consumer interconnection. It is intended to cover applications involving service to a consumer that normally requires a transformation between the utility’s supply voltage and the consumer’s utilization voltage. Interconnections supplied at the utilization voltage are not covered. This guide is not intended to supplant specific utility or consumer practices, procedures, requirements, or any contractual agreement between the utility and consumer. The examples of interconnection protection of varying complexities that have been provided are used for illustrat...

The primary purpose of this guide is to help those who are responsible for the application of protective relaying for the electrical interconnection between utility and consumer systems. It is anticipated that representatives of the utility, the consumer, and their consultants who are responsible for the specification, design, and operation of the interconnection will use this guide. Recognizing the diverse audience being addressed, background information is included in a bibliography to direct the reader to more complete treatment of the material.