In homes, the best height for installation is about 1. 5 meters from the floor — it's easy to reach and out of children's reach. SEC Distribution System extends from the MV (33 kV, 13. 8 kV) feeder outlets of HV / MV Substations down to SEC Customer interface including KWH-Meters and meter boxes. To provide. This document represents the minimum requirements and specifications for the installation of the electrical underground distribution systems fed from overhead transformation, serving Secondary Service Accounts, to be transferred to Oncor Electric Delivery Company ownership. REFERENCES This. 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. The Third party designs and constructs the substation.