Electricity is generated by burning gas, coal or oil, by water or hydroelectric power, or by nuclear power. The distribution of power to homes varies in different countries, but in Britain the voltage from the power station is between 100,000 and 400,000 volts. The electricity is carried on cables strung between high pylons, where insulators prevent it from escaping to the ground. The cables are connected across the country in a system called the National Grid. If there is a fault with one power station, power can still be obtained from the grid.
The electricity is drawn off in substations, which reduce it to 240 volts. This voltage is used through most of Europe, while in North America 120 volts are used.
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