UK

Here, the frequency (as in the whole of Europe) is 50 Hz and the residential supply is 230-240 V single phase. The European standard is now 230 V, but with ±10% tolerance this voltage can vary between a maximum of 253 V and a minimum of 207 V; equipment and appliance designers must take this allowed variation into account or beware! Most commercial and industrial loads are supplied at 400-415 V or higher voltages, three phase. The winter load produces the highest peak because of the preponderance of heating appliances, although it is noted that the summer load is growing due to increasing use of air-conditioning in commercial and industrial premises.

Continental Europe

Many continental countries still mainly have combined generator/transmission utilities, which cover the whole country and which are overseen by government control. Increasingly these systems are being 'unbundled', that is they are being separated into different functions (generation, transmission, distribution), each individually accountable such that private investors can enter into the electricity market (see Chapter 12). Interconnection across national boundaries enables electrical energy to be traded under agreed tariffs, and limited system support is available under disturbed or stressed operating conditions.

The daily load variation tends to be much flatter than in the UK because of the dominance of industrial loads with the ability to vary demand and because there is less reliance on electricity for heating in private households. Many German and Scandinavian cities have CHP plants with hot water distribution mains for heating purposes. Transmission voltages are 380-400, 220, and 110 kV with household supplies at 220-230 V, often with a three-phase supply taken into the house.

China and the Pacific Rim

The fastest-growing systems are generally found in the Far East, particularly China, Indonesia, the Philippines and Malaysia. Voltages up to 500/750 kV are used for transmission and 220-240 V are employed for households. Hydroelectric potential is still quite large (particularly in China) but with gas and oil still being discovered and exploited, CCGT plant developments are underway. Increasing interconnection, including by direct current, is being developed.

 
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