Page 658 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

The City & Guilds Textbook: Plumbing Book 1

A network of circuits, overhead lines, underground cables and substations link
the power stations and allow large amounts of electricity to be transmitted
around the country to meet demand. Local distribution networks operate at
132 kV, 66 kV, 33 kV and 11 kV. Alongside local distribution there are high-
voltage transmission networks operating at 400 kV (the super grid) and 275 kV
(the grid). Primary substations feed supplies at either 66 kV or 33 kV – typically
to supply larger industrial installations and the secondary distribution networks
in urban and rural areas. Secondary substations connect at low voltages,
230–400 V via overhead line on wooden poles or underground cables.

Power station
25 kV 400/275 kV
Very large factory
33,000 V

Large factory
11,000 V

Civic buildings and hotels
400/230 V

Large farm
11,000 V

Transformed Hospital
Houses 11,000 V to 11,000 V
230 V 400 to 230 V

Transformed Transformed
132,000 V 33,000 V
to 33,000 V to 11,000 V

p Figure 11.3 Electricity journey map

The supply of electricity into the home is known as single phase. As mentioned
in the previous section, the electricity distributed to factories is three phase –
single-phase electricity for domestic use is taken from this.
You should also be aware that in domestic properties you actually get 230 V,
rather than 240 V (which you may see it referred to). In older industrial settings
you may see signs specifying 415 V, however since 1995 the nominal industrial
supply voltage has been 400 V. This is three-phase supply, which you will not be
qualified to work on.

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