2. Equipment in Power Systems

Electricity is supplied to a large number of households, offices, and factories every day. Its availability has increased over the last 100 years since electricity has begun to be supplied in the late 1800s, and nowadays it is considered to be an essential commodity. It is a versatile and clean source of energy; it is rather cheap and “always available.” The purpose of a power system is to transport and distribute the electrical energy generated in the power generation plants to the consumers in a safe and reliable way, no matter how far the power generation plants are located from the load. In most cases, alternating current (AC) technology is used for electrical energy transportation, and in a minority of the applications such as a point-to-point international connection and long-distance, large-capacity transportation, direct current (DC) is preferred. The advantage of an AC power system lies in the fact that the voltage can easily be brought to a higher level in order to reduce losses during energy transportation. Figure 2.1 shows a typical AC power system including power generators, power transformers, and substation equipment such as circuit breakers.