The purpose of this guide is to provide guidance to the substation engineer in established practices for the application and installation of metallic and optical cables in electric power transmission and distribution substations with the objective of helping to minimize cable failures and their consequences. This guide emphasizes reliable electrical service and safety during the design life of the substation. Regarding cable performance, no single cable characteristic should be emphasized to the exclusion of others. In addition to good installation, design, and construction practices, an evaluation of cable characteristics is necessary to provide a reliable cable system. Solutions presented in this guide may not represent the only acceptable practices for resolving problems. This guide should not be referred to or used as an industry standard or compliance standard. This document is presented as a guide to aid in the design of insulated wire and cable system installations in substations.