Substation
[edit] Introduction
In electrical engineering, a substation is a facility housing equipment that switches, transforms or converts high voltage electricity from a generating station into lower voltages that are easier and safer to distribute to homes, shops, small businesses and other consumers. This is necessary as it would be uneconomical and possibly dangerous to connect consumers directly to the main distribution network – they use small amounts of electricity in relation to industry and commerce – so it is 'stepped down' to a suitable voltage (240V AC in the UK) for local distribution.
Substations may also transform low-voltage electricity into higher voltages where large amounts of electricity are required, e.g a neighbourhood with numerous multi-storey buildings.
Sub-stations vary in size according to the type and number of customers they serve – they are usually larger if they serve commercial and industrial units, and smaller for residential neighbourhoods.
The equipment is typically freestanding, unprotected from the weather and cordoned off with a wire fence. The public is explicitly forbidden from entering and is alerted by signs warning of possible death by electrocution. Some substations are very close to houses and others even on customers’ land.
[edit] Magnetic fields
The equipment inside a substation produces a magnetic field but this reduces rapidly with distance, and by the time it reaches the perimeter fence it approaching background levels (i.e very low levels measured in microteslas (µT) – an SI unit of magnetic flux density equal to 10−6 teslas). The electrical lines entering a substation, whether underground cables or overhead lines, produce the highest magnetic field around the substation.
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