The secondary box adopts an inner and outer door design, with a spray painted exterior. It is safe and aesthetically pleasing, and the rainproof top of the box is suitable for outdoor work. The wiring color codes are the standard safety language of electricity. They make it easy to identify immediately which wires are live, neutral, or grounded (avoiding costly mistakes and hazardous accidents). Proper identification prevents hazards, streamlines maintenance, and ensures. With secondary selective service, each distribution transformer must be able to supply the entire load for maximum reliability benefits. 8 & 33 KV Metered Ring Main Unit SF6 Room Sub-station.