The operations for connecting to the electricity mains must be carried out by a qualified electrical installer.

所有的安装及连接须由合资格的电子装配员操作。

youdao

The electricity supply has been cut off at the mains.

电的供应在电源处被切断。

《牛津词典》

The house is far from water mains and electricity and relies on its own generators.

这座房子远离自来水总管和供电网，依靠自备的发电机。

《柯林斯英汉双解大词典》

In the 70s when I was away from a mains electricity supply, a 12-volt battery would keep my respirator operating for just 20 minutes.

CNN: 'I lived in an iron lung for seven years'

But it is a particularly good idea for an electric car because mains electricity can be used if the car is still plugged in, thus conserving battery power.

ECONOMIST: Vehicle telemetry

The city's police are largely untrained and corrupt, only eight of 120 stipulated judges are doing their jobs, and mains electricity and water are, for many Kandaharis, a rare treat.

ECONOMIST: Afghanistan