Substations are a familiar sight alongside highways and in cities. Substations take the electricity from power plants and from the transmission lines and transform it from high to lower voltage. They distribute electricity to consumers and supervise and protect the distribution network to keep it working safely and efficiently, for example by using circuitbreakers (the industrial strength equivalent of the humble fuse) to cut power in case of a problem.
Substations are often classed according to the switchgear used to protect their circuits.
● Air-insulated switchgear (AIS ) used to be the most common design, but this requires a lot of space and for higher voltages is only feasible outdoors. Even then, AIS may be unsuitable or undesirable in certain locations, such as residential areas.
● Gas-insulated switchgear (GIS ) may be more expensive if only the unit cost is compared, but is safer and needs less maintenance. The fact that GIS units are five times smaller than AIS means cost savings and smaller, less intrusive buildings.
Electrical lines can be overhead or underground. The construction of overhead lines costs less, but outages are more common than on underground lines (due to bad weather, lightning strikes or accidents).
What do we find in a substation? Power transformers, switching devices such as circuit breakers and disconnectors to cut power in case of a problem, and measurement, protection and control devices needed to ensure its safe and efficient operation.