IEEE 1050-1996 Historical

The typical environment in a generating station provides many sources of electrical noise, such as the switching of large inductive loads, high fault currents, static switching, and high-energy, high-frequency transients associated with switching at the generator or transmission voltage level. The increasing use of solid-state equipment, computer- or microprocessor-based control, and signal multiplexing systems in these applications introduces a number of specific concerns with respect to electrical noise control. This guide discusses methods for the grounding of instrumentation and control equipment and their associated circuits in generating stations. It is intended to provide guidance for the design of grounding systems for instrumentation and control equipment specific to the generating station. The low-level electrical signals transmitted from various instrumentation and control equipment in a generating station through long cables may undergo signal distortion as they travel to the receiving end. This distortion is typically caused by noise pickup either at the signal source or along the cable run. The level of noise on the received signal can cause errors in measurement and control functions (and in extreme cases, damage to equipment), which in turn may result in costly unit downtime. The use of proper grounding along with proper shielding techniques can solve a large percentage of noise problems. It should be recognized that there are numerous accepted grounding techniques and that the actual installation of a ground system should be made in consultation with instrumentation and control equipment manufacturers. The grounding methods in this guide are intended to minimize degradation of instrumentation and control signals in generating stations. By contrast, the station grounding system is mainly oriented toward meeting the requirements of various safety codes that aim to establish a grounding system that will provide a low-impedance path to ground. This low-impedance path helps to ensure that high voltages are not developed on equipment or structures as a consequence of lightning surges, electrical faults, circulating currents, or static charges. This guide is complementary to IEEE Std 665-1995 .