Selection Guide for Overhead Distribution Transformer Protection

This guide provides detailed information on the selection and application of S&C Type SMD-20 Power Fuses for overhead distribution transformers. It outlines the fuse's role in protecting transformers rated from 5 kVA to 1500 kVA against a range of secondary-side faults and coordinating with overcurrent protective devices. The guide emphasizes the importance of selecting the appropriate fuse unit to accommodate normal loading schedules, including peak loads and inrush currents. It includes fuse-selection tables that facilitate the direct selection of fuse units based on transformer ratings and loading conditions. The tables also quantify the transformer protection level provided by the fuse units using the Transformer Protection Index. Additionally, the document discusses the factors influencing fuse selection, such as compliance with coordination requirements and the need to verify voltage ratings and interrupting ratings. This comprehensive approach ensures optimal protection and coordination within distribution systems.