MainS

Mains refers to the principal electrical supply that delivers electricity to buildings from the public distribution network. It is typically an alternating current (AC) supply provided at a standard voltage and frequency suitable for residential and commercial use. The term is common in the United Kingdom and other English-speaking countries; in the United States and some regions, terms like household electrical system or power grid are more often used.

Regional standards vary. Domestic mains are usually single-phase in homes, though three-phase supplies are used for larger loads. In North America, typical domestic mains are around 120 V RMS at 60 Hz, with higher voltages such as 208–277 V available on three-phase systems. In Europe, much of Asia, and many other areas, the standard is about 230 V at 50 Hz. The wiring generally includes a live (hot) conductor, a neutral conductor, and a protective earth (ground) conductor. The live conductor provides the voltage relative to neutral, while earth supports fault current for safety.

Delivery and infrastructure involve a multi-stage system. Electricity is generated at power stations, transformed to higher voltages for transmission, and then stepped down by substations for distribution. The building receives power through a service entrance, which typically includes a meter, a main protective device (fuse or circuit breaker), and a distribution board that feeds individual circuits. In some regions a single main disconnect is required.

Safety and regulation govern mains installation and usage. Electrical codes dictate proper wiring, grounding, insulation, and protection devices such as fuses, circuit breakers, and residual current devices. Safe handling and professional installation are advised for any work on mains wiring, given the risk of shock and fire. Outages or faults can disrupt or endanger the supply.