scope:

This application guide was developed to identify instrumentation and control (I & C) equipment grounding methods to achieve both a suitable level of protection for personnel and equipment, and to provide suitable electric noise immunity for signal ground references in generating stations. Both ideal theoretical methods and accepted practices in the electric utility industry are presented. Special applications relating to advanced energy storage and conversion technologies (photovoltaics, fuel cells, etc.) have not been considered.

This guide is intended to provide information about grounding methods for generating station I & C equipment. Grounding design is normally based on the concept of two separate grounding systems: the equipment ground and the signal reference ground. The grounding of instrument chassis, racks, cable sheaths, or cable shields and signal pairs requires special care to ensure that personnel working on equipment are adequately protected against electrical shock hazards during both normal and abnormal conditions, as well as to ensure that interference signals are not inadvertently coupled into signal circuits.

The basic theory and guidelines to be understood before designing I & C grounding are presented in clause 4. Clause 5 provides guidance for grounding of equipment associated with generating station I & C systems and presents various approaches to providing a signal ground system. Clause 6 presents accepted practices in grounding the shields of I & C cables, while clause 7 covers the testing of I & C grounding systems.