Voltage regulators: to keep the voltage within permissible limits at the receiving end.These include ground wires, lightening arrestors, circuit breakers, relays etc. Protective devices: to protect the transmission system and to ensure reliable operation.Support towers: to support the line conductors suspending in the air overhead.Line insulators: to mechanically support the line conductors while electrically isolating them from the support towers.Transformers permit power to be transmitted at higher efficiency. Transformers: Step-up transformers are used for stepping up the voltage level and step-down transformers are used for stepping it down.Usually, ACSR (Aluminium-core Steel-reinforced) conductors are used. Conductors: three for a single circuit line and six for a double circuit line.Following are the main elements of a typical power system. Its emphasis is on communicating the functions of the power equipment and the associated protection and control system. Usually, overhead transmission system is used.ĭue to the economic considerations, three-phase three-wire overhead system is widely used for electric power transmission. The single line diagram (SLD) is the most basic of the set of diagrams that are used to document the electrical functionality of the substation. The choice of transmission system is made by keeping in mind various factors such as reliability, efficiency and economy. Since conductor cost is a major part of the total cost, it has to be taken into consideration while designing. Also, the cost of conductor material required is one of the most considerable charges in a transmission system. However, it is to be noted that, the cost of constructing underground transmission lines highly depends upon the local environment. But, construction of an underground transmission line generally costs 4 to 10 times than an equivalent distance overhead line. single phase, two wires with midpoint earthedĮlectric power transmission can also be carried out using underground cables.The secondary distribution system consists of feeders, distributors and service mains. End consumers are supplied through a service mains line from distributors. Finally, the voltage is stepped down to 415 volts by a pole-mounted distribution transformer and delivered to the distributors. ![]() ![]() There are three breakers for every two connections of lines or transformers to the bus, i.e. The arrangement of figure two is called a breaker and a half. Feeders are either overhead lines or underground cables which carry power close to the load points (end consumers) up to a couple of kilometers. Single line diagrams like in figure 2 are used to illustrate the layout of buses in a substation.
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