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Developed and maintained by the NFCC

Substations

Information

A substation is a part of an electrical generation, transmission and distribution system.

Substations transform voltage from high to low, or the reverse, and perform any of several other important functions. Between the generating station and consumer, electric power may flow through several substations at different voltage levels.

Substations may be owned and operated by an electricity supplier or may be owned by a large industrial or commercial customer. Generally, substations are unattended, relying on remote supervision and control.

A substation may include transformers to change voltage levels between high transmission voltages and lower distribution voltages, or at the interconnection of two different transmission voltages.

High-voltage network substations

A high-voltage network substation is a large installation where 275kV and 400kV overhead power lines or underground cables are switched and where electricity is transformed to 132kV for distribution to surrounding areas. Each substation can be 100 metres or more across and surrounded by a metal fence; a few are indoors in suitably large buildings.

Intermediate substations

These substations transform electricity between 132kV, 33kV and 11kV. They are smaller than high-voltage network substations but bigger than the final distribution substations that transform the electricity from 11kV to the 400V or 230V supplying homes and workplaces.

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Final distribution substations

These transform the electricity from (usually) 11kV to the voltage used in the home, 230V. There are several different types:

Indoor - in a small building, which may look like a garage, or as part of a larger building. They may be identified by the safety sign on the door.

 

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Cabinet - built into a fully enclosed cabinet

 

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Outdoors - the separate components are mounted on the ground and enclosed by brick walls or metal/wooden fences

 

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Pole-mounted - the transformer is raised above ground on a wooden pole

 

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These are easy to recognise due to their construction and location. In addition, utility companies provide ample signage warning of high voltages and relevant dangers.

Hazards (for further information refer to National Operational Guidance: Utilities and fuel)

  • High risk of electrocution for anyone entering the perimeter of the substation
  • Electrocution, which can occur without physical contact with equipment
  • High-voltage lines entering the substation, both overhead and underground
  • Open high-voltage busways or buswork (conductors, wire and aluminium pipe) criss-crossing the station at a relatively low height
  • Oil-filled switchgear, transformers, regulators and capacitors, which, once alight, will need to be fully isolated before firefighting operations are commenced
  • Smoke and gases due to burning oil and insulating materials
  • Collapsed steel framework and aluminium buswork caused by the intense heat of a fire
  • Explosions from oil-filled equipment, both overhead and at ground level
  • Exploding glass and porcelain insulators, throwing fragments with considerable force

References and further reading

www.emfs.info/sources/substations/