The insulation coordination standard and guide apply to three-phase ac systems above 1 kV and are divided into two parts. IEEE Std 1313.1-1996 (Part 1) specifies the procedure for selection of the withstand voltages [basic lightning impulse insulation level (BIL) and basic switching impulse insulation level (BSL)] for equipment phase-ground and phase-phase insulation systems. It also identifies a list of standard insulation levels. Although he principles of this standard also apply to transmission line insulation systems, the insulation levels may be different from those identified as standard insulation levels. This guide (Part 2) 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. The guide is intended for air-insulated ac systems; caution should be exercised in the case of gas-insulated systems (GIS).