The protection circuit is adopted to prevent the occurrence of the external circuit fault supplied by the distribution box. For example, da88cm-ii motor phase loss protection module can be installed in the distribution box to prevent the motor from burning due to. Surge protectors (Surge Protective Devices, SPD) installed in distribution board panels are primarily used to protect electrical equipment from transient voltages (surges or spikes) caused by lightning strikes, power grid fluctuations, or other factors. Depending on the application and protection. Primary distribution systems consist of feeders that deliver power from distribution substations to distribution transformers. Many feeders leave substation in a concrete ducts and are routed to a nearby pole. At this. Abstract: To protect personnel, equipment, and maintain continuity of service for an electrical system, protection or fault interrupting devices are required. 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.