How do they meter 3-phase?

25 Jan 2004
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United Kingdom
After a thread regarding running single phase equipment off one phase of a 3-phase supply, I was thinking to myself. "How do they meter 3-phase electricity in small workshop premises?". Do the meters have a 3-phase to single phase transformer? Or do they just meter phase A and assume that B and C are under the same load?

Oh, and can anyone foresee the introduction of 3-phase supplies into new UK homes? With Part P looming it is going to become more prudent to hire in qualified sparks to do your home electrics so what difference is it to get them to attend to 3-phase installations over single phase? And with the advantages it can bring for high-powered appliances (namely ovens and electric showers) then I reckon this COULD become not too unusual in large luxury homes in 10 years. :?:
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plugwash said:
afaict they use 3 seperate meters

Only if the supply is split into three single phase supplies.

To meter 3 phase there are two methods,

For supplies up to 125A per phase, they can use a single meter connected as standard.

For supplies OVER 125A per phase, they tend to use meters connected via CT chambers.

CT = current transformer
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If it's an electro mechanical meter, there will be three disks on one axle, so each phase adds to the rotation. If it's a newer electronic meter, all three phases will be measured.

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