mains electricity meaning in Chinese

市源

The hum of mains electricity is causing this gentleman some discomfort
电流发出的嗡嗡声让这位办公室职员快崩溃了。
Should we implement measures to facilitate access for re suppliers to the main electricity power grid
我们应否制定措施，让可再生能源电厂能接上主要的电网？
Next year hainan island is expected to be linked to the main electricity network in the south of the country and at that time will also be part of a competitive market the serc said
电监会称，明年海南岛也将与华南的主供电网络相连。到时候，海南也将成为市场竞争的一部分。