Terminology and Power Systems
– Mains electricity is referred to by different names in different countries.
– Power systems vary worldwide in terms of voltage, frequency, plugs and sockets, earthing system, and protection against overcurrent damage.
– Different standards may be used in foreign enclaves or city areas.
– Some regions may have no central electrical authority and rely on private sources for power.
Building Wiring
– Portable appliances use single-phase electric power with two or three wired contacts at each outlet.
– Residential electrical supply in northern and central Europe is commonly 400V three-phase power.
– Small portable electrical equipment is connected through flexible cables terminated in a plug.
– Larger household and industrial equipment may be permanently wired to the building’s fixed wiring.
Circuit Protection
– Circuit breakers and fuses are used to detect short circuits and prevent overheating and fire.
– Residual-current devices are used to detect ground faults and quickly cut off the circuit.
– Ground faults refer to the flow of current in other than the neutral and line wires.
Voltage Levels and Measuring Voltage
– Most of the world population uses a supply that is within 6% of 230V.
– The nominal supply voltage in the UK and Australia is 230V +10%/-6%.
– A distinction between the voltage at the point of supply and the voltage rating of equipment.
– Utilization voltage is typically 3% to 5% lower than the nominal system voltage.
– Voltage drop occurs between equipment and supply.
– Power distribution system voltage is nearly sinusoidal in nature.
– Voltages are expressed as root mean square (RMS) voltage.
Standardization and History
– European countries shifted towards a standard European voltage of 230±23V.
– The UK still has areas with 250V for legacy reasons.
– Australia converted to 230V as the nominal standard with a tolerance of +10%/-6%.
– The United States and Canada have a nominal voltage of 120V with a range of 114V to 126V.
– Japan uses 100V and 200V for electrical power supply to households.
– The world’s first public electricity supply was a water wheel driven system in Godalming, England in 1881.
– AC systems started appearing in the US in the mid-1880s, using higher distribution voltage stepped down via transformers.
– After World War II, the standard voltage in the US became 117V, but many areas lagged behind.
– Different regions in Japan operate at different frequencies, 50Hz and 60Hz.
– Newly developed metal filament lamps have higher voltage capability.
– In the first decade after the introduction of alternating current in the US, different frequencies were used.
– Westinghouse Electric Company in the US and AEG in Germany standardized their generation equipment on 60Hz and 50Hz respectively, leading to most of the world being supplied at one of these two frequencies.Sources: https://en.wikipedia.org/wiki/Mains_electricity
