Mains Electricity - Mains Power Systems

Mains Power Systems

For a list of voltages, frequencies, and wall plugs by country, see Mains electricity by country

Worldwide, many different mains power systems are found for the operation of household and light commercial electrical appliances and lighting. The different systems are primarily characterized by their

• Voltage
• Frequency
• Plugs and sockets (receptacles or outlets)
• Earthing system (grounding)
• Protection against overcurrent damage (e.g., due to short circuit), electric shock, and fire hazards
• Parameter tolerances
• Single-phase or Three-phase electric power
• Alternating current (AC) or Direct current (DC) (DC has been almost completely converted to AC since the mid 20th century, but DC was the general rule in the past)
• The general characteristics of the general power distribution network (problems with computers in 230V nets)

All these parameters vary among regions. The voltages are generally in the range 100–240 V (always expressed as root-mean-square voltage). The two commonly used frequencies are 50 Hz and 60 Hz.

Foreign enclaves, such as large industrial plants or overseas military bases, may have a different standard voltage and frequency from the surrounding areas. Some city areas may use standards different from that of the surrounding countryside (e.g. in Libya). Regions in an effective state of anarchy may have no central electrical authority, with electric power provided by incompatible private sources.

Many other combinations of voltage and utility frequency, including direct current, were formerly used, with frequencies between 25 Hz and 133 Hz and voltages from 100 to 250 V. The modern standard combinations of 230 V/50 Hz and 120 V/60 Hz did not apply in the first few decades of the 20th century and are still not universal.

Industrial plants with polyphase power systems will have different, higher voltages installed for large equipment (and different sockets and plugs), but the common voltages listed here would still be found for lighting and portable equipment.