Each secondary unit substation is an assembled unit consisting of a transformer, an integrally connected primary fused switch, and low-voltage switchgear or switchboard. Circuits are fed to each load from circuit breakers or fused switches. 1 This document is one of a suite of documents intended for designing and installing substations for adoption, and/or for use, by Scottish and Southern Electricity Networks (SSEN) Designers and Installers, covering the following situations. However, the key to. Abstract: The electrical point of interconnection with a utility can vary in voltage level whether it be secondary, primary, or transmission voltages. Additionally. Level 1 required configuration: Main circuit isolation + main circuit breaker and main fuse Shunt isolation + shunt leakage protection switch Level II required configuration: Main circuit general isolation + main circuit fuse and circuit breaker Shunt isolation + shunt fuse and circuit breaker.
