According to the different requirements of electrical equipment for power supply reliability, the power supply load is divided into three grades.
1. Main load
The load that will cause great political and economic losses or casualties due to power supply interruption is called Class I load. Such as important railway hubs, communication hubs, important international venues, important hotels, operating rooms in hospitals, and important biological laboratories.
In addition to two independent grid power supplies, the power supply mode of primary load should also be equipped with standby power supply. The standby power supply is generally a diesel generator set or a DC battery set.
2. Secondary load
The load that power supply interruption will cause great political and economic losses or cause disorder in public places is called secondary load. For example, office buildings of local municipal governments, three-star hotels, first-class cinemas, libraries, museums, cultural relics and treasures at the prefecture level.
Except for two independent lines, the secondary load should provide standby power supply according to the actual situation.
3. Tertiary load
Except for the primary load and the secondary load, the rest belong to the tertiary load. The third-class load has no special requirements for power supply mode, and generally adopts single-loop power supply.
With the development of China's economy, the first-class load power supply mode can no longer meet the needs of some particularly important places, such as local telephone offices, telecommunications hubs, satellite ground stations, civil airports, bank securities trading centers and so on. These loads are particularly important first-class loads, which are generally called special first-class loads. At the same time, due to the development of economy and the increase of primary load and secondary load, the power supply mode of tertiary load will be gradually reduced or cancelled.