|MadSci Network: Engineering|
A substation is basically a power switching facility. Transmission lines coming from generating stations or other substations are connecter to switches called "circuit breakers" or just "breakers." The substation design usually includes a bus system, either in a parallel or ring configuration. A bus is just a solid stiff wire that looks like a pipe, but it is connected to its support structure by brown, tapered and ribbed insulators. The length of the insulators is dependent on the voltage involved. The higher the voltage, the longer the insulator. As you look at a substation, you should see the incoming and outgoing transmission lines in groups of three because the power is three-phase AC. There is a small wire at the top of the transmission tower above the center of the three main conductors. This is called a "telemetering line," and it is the line that is usually hit by lightening, so if you follow it into the sub station you will find it is connected to a very long brown insulator that is not tapered called a "lightening arrestor." It's job is to shunt any lightening that doesn't go to ground through the transmission tower steel away from the main conductors. Some substations will have transformers if there is a need to change voltage. The need to change voltage depends on customer needs, and in some cases, is required to connect a new higher voltage transmission system to an older, lower voltage one. Transformers are usually large and have cooling pipes and sometimes fans on the outside. They will have six insulators on top connected to the incoming and outgoing transmission lines or to the buses, but breakers also have six insulators. The breakers are smaller and the insulators are all the same length. The transformer insulators are different lengths depending on the voltage. Older substations may have a building used to contain controls for the breakers and instrumentation to monitor the conditions of the insulating oil within the tanks housing the transformers and breakers. Newer technology has reduced the size of that equipment to a small box mounted directly on the transformers and breakers that sends the information to a central control station usually the System Operating Center.
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