Most power companies normally supply a certain area of households and housing estates with 3-phase power and then divide it and dispense it as individual single phase supplies per street or group of streets, giving each house in each street single phase power.
Most power companies can provide 3-phase power to households or establishments if needed. This is very advantageous for businesses such as vehicle repair garage, factories, engineering workshops etc that need to power heavy machinery and equipment, such as power tools where motors are installed in the machinery.
The deliverance of the type of power supplied to a building (single phase or three phase) from the street depends on the building’s usage requirements: an industrial site or factory which uses powerful machinery and large power tools, etc., will usually require electricity delivered as 3-phase power. Small offices and domestic buildings usually only power single-phase appliances and lighting, so only require a single-phase power supply from the street.
Typically the electrical power is produced at the power station in three individual phases. The live wires (L1, L2 and L3) of each of the phases are timed to delay each other in wave and cycle periods as follows: the first phase live wire (L1) is produced at Zero degrees, which is equal to 360o, the 2nd phase’s live wire (L2) is timed to lag the first phase’s live wire (L1) by 120o and the live wire (L3) of the third phase is timed to lag the first phase’s (L1) by 240o. Typically, in most European countries the colours of the live wires are brown for L1, black for L2 and grey for L3 and blue for the neutral wires.
The reason why energy supply companies use 3 phase transformers to transmit their energy is due to the efficiency and low running cost of the transformers. 3 phase transformers provide a constant supply of energy and because of the way they operate, 3 phase transformers are low maintenance and make little noise. Typically large power generators provide electric currents at up to 30KV and at the power stations; this is increased for the suitability of the transmission process.