scope:

The insulation coordination standard and guide apply to three-phase ac systems above 15 kV and are divided into two parts. This guide, the second part, is an application guide with practical examples, intended to provide guidance in the determination of the withstand voltages and to suggest calculation methods and procedures. The insulation coordination examples for selected equipment are designed to explain the principles of Part 1, IEEE Std C62.82.1. The guide is intended for air-insulated ac systems. Caution should be exercised in the case of gas-insulated systems (GIS).

Purpose

It should be recognized that absolute protection of station equipment is theoretically impossible. Even if arresters are located at the terminals of all apparatuses, equipment failures can occur. The probabilistic method, that is, designing for a mean time between failures (MTBF) criterion, is proposed here not only to permit a realistic basis of design but also perhaps more importantly to form a consistent measure of design based on reliability.