Can anyone explain why.......?

[topt]

I am sure there is a simple explanation but electrical theory is not a strong point for me so would be grateful if someone could shed some light 9sorry no pun intended).

Moobahn with about 50 houses. Yesterday early evening returned to find we had no power to some parts of the house. So downstairs the kitchen had everything working, no lights in the toilet next to it but power and lights to half of the downstairs including one of the A/Cs.

Upstairs some lights but sockets and A/C not working.

Couple of times switching on lights there was a faint glow for a few seconds then nothing.

Eventually all was back on late in the evening. No idea still what caused it this time.

All sockets in the house are 3 pin.

One other house across the soi from us and 3 houses up had no power at all. Do not know of anybody else with an issue but they may have done. This happened once before when a box went up in flames at the end of the soi and affected one of the (transformers?) that is supported about 20feet up.

I could not understand then how we had power in places but not everywhere. If there was enough to power an A/C, when it was not on, why would other lights not work?

[swoods58]

You have 3 phase powere and 1 or 2 phases were down. The houses with no power have single phase power and connected to the down phases.

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[topt]

Maybe but my guess is all the houses would be the same.

Sorry but can you explain how this 3 phase works - do we have 3 different wires coming into the house from the meter each carrying power and linked to certain circuits?

[KhunBENQ]

No.

There are 3 phases on the poles, but your house is connected to only one of them (via a transformer, 230 Volt).

That is true for most private consumers. Rarely that private houses are "3 wired" (400 Volt).

Other houses might be connected to another phase.

Not so unusual these "effects".

We had similar about two weeks ago.

Difficult to interpret in the first place.

Edited May 1, 2014 by KhunBENQ

[Crossy]

How many wires from the pole to your home?

Two = single-phase

Four (yes 4) = three-phase (Thailand is three-phase 4-wire)

If you are single phase it's possible that the supply was very low voltage and some equipment worked but other stuff didn't.

[topt]

How many wires from the pole to your home?

Two = single-phase

Four (yes 4) = three-phase (Thailand is three-phase 4-wire)

If you are single phase it's possible that the supply was very low voltage and some equipment worked but other stuff didn't.

From the meter box (mounted on the pylon that carries the main cables) on the other side of the soi there are 4 separate conduits going into one big pipe that then goes under the road to the house so I am guessing 4. There are 4 wires going in to the meter and 4 wires coming out going into the conduits.

[swoods58]

If you have four wires to the street then you have 3 phase. Each house circuit is connected to different phases to balance the load. Also can give approximately 400 volts for some specialised equipment that may need it, e.g. air conditioners

[topt]

If you have four wires to the street then you have 3 phase. Each house circuit is connected to different phases to balance the load. Also can give approximately 400 volts for some specialised equipment that may need it, e.g. air conditioners

Thanks - that's clearer.

I am curious why there are 4 wires but it is called 3 Phase?

[Crossy]

If you have four wires to the street then you have 3 phase. Each house circuit is connected to different phases to balance the load. Also can give approximately 400 volts for some specialised equipment that may need it, e.g. air conditioners

Thanks - that's clearer.

I am curious why there are 4 wires but it is called 3 Phase?

Three phases plus neutral = 4 wires.

Some 3-phase appliances (aircon for example) may only have 3 wires as the neutral is not used (with a balanced load the neutral carries no current so can be omitted).