Electricity is transported through a system of overhead or underground cables and wires, and substations, which adjust voltage. After generation, the voltage of electricity is increased at a generation substation to allow it to travel long distances. The long distance lines used are known as the national grid. Once closer to the point of use, a grid supply point substation reduces the voltage. The electricity is then carried by distribution lines to homes and businesses. A small number of users of very large amounts of electricity are directly connected to the national grid. These users have dedicated substations. Different companies handle the generation, distribution and selling of electricity. Transpower, a state owned enterprise, is responsible for the national grid and electrical transmission through it.