GB 50052-2009 第3.2.8条
| The power supply system for Grade II loads should preferably be supplied by two circuits. When the load is small or the regional power supply conditions are difficult, Grade II loads may be supplied by a single dedicated overhead line or cable of 6kV or above. When cable circuits are used, the supply should consist of two cables, each of which should be capable of carrying 100% of the Grade II load.