Minimum distance between any part of MV ground system and nearest LV neutral ground shall be 4 meters. Before deciding to install ground wire in place of ground rods it should be investigated if normal (non rocky soil) soil is available with in a reasonable distance (up to 50 meters) from the installation and along the cable trench. Generally, distribution boxes can be divided into three levels of secondary protection, that is, three levels of distribution boxes: general. The distance between the distribution box and the switch box should not exceed 30 meters, and the horizontal distance between the switch box and the fixed electrical equipment it controls should not exceed 3 meters. This proximity principle reduces line losses and improves power supply efficiency. This document represents the minimum requirements and specifications for the installation of the electrical underground distribution systems fed from padmounted transformation, serving Secondary Service Accounts, to be transferred to Oncor Electric Delivery Company ownership. REFERENCES This. secondary unit substation is a close-coupled assembly consisting of enclosed primary high voltage equipment, three-phase power transformers, and enclosed secondary low-voltage equipment. The following electrical ratings are typical: As a result of locating power transformers and their close-coupled. In this guide, we'll break down everything you need to know to install a distribution box correctly and confidently. Choose the right box based on environment (indoor/outdoor), load capacity, and durability. Ensure safe placement: install in.