subject: Switchgear Types [print this page] In any electrical system, there needs to be a set of fuses and switches that are available to shut down the electrical equipment in case of an emergency or for maintenance. This is clearly a necessary part of an electrical system because you have to be able to shut everything down from a remote location if there is an emergency. This set of switches is called switchgear.
Although switchgear panels have been in use since the early days of electricity, the technology has advanced substantially over the years. Until fairly recently, the switchgear systems required a manual shutdown, which involved sending someone to turn the switches off. This can be dangerous if there is an emergency underway, and the delay implied in that situation is unacceptable in an emergency.
The switchgear must be insulated in order to perform adequately. In smaller systems, this is achieved by having the switchgear in a fenced in area outdoors. This requires a large open air space and this will only work in small systems. Because this is not feasible for all systems, however, there are several alternative insulation options available.
Oil was a popular insulator for a long time but as other options became available people largely moved away from oil as an insulator due to the risk posed by oil spills in proximity to large electrical systems. This insulation system is achieved by shooting vaporized oil through the electric arc, breaking the connection. This is an effective solution for the switchgear, however, there are other effective solutions that are less dangerous.
Gas insulators are safe and effective, but they are also expensive due to the special gas required to have gas powered switchgear. The circuit breaker stretches the electrical arc using magnetic fields and when it gets stretched enough the gas will be able to break the connection.
Another insulating method is vacuum insulation. In this situation, the vacuum insulation quenches the electric arc. This only works in medium voltage situations because there vacuum insulation is not strong enough or stable enough to handle higher voltage situations. The electric arc is compressed in this system as vacuum insulation requires very little stretching in order to extinguish the current.
Another option is a compressed air insulated system. In this system the air elongates the electrical arc until it is unable to sustain itself and extinguishes itself. This is a simple system and effective in many voltage arrangements. This is obviously not at all the same as the open air system discussed earlier.
Switchgear is a necessary safety device for any electrical system.
