I have a 3x230V electrical system in my house. Every circuit has 2 fuses (one at both ends). On one of the circuits one fuse is switched off, but my lights kept working (although at half their strength). I measured the voltage of the circuit and it was 130 Volt. Is this caused by an unwanted contact and if so how could I find it?
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2You might want to add what country you are in. There are a few different electric systems out in the world.– JPhi1618Commented Oct 22, 2019 at 15:46
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1Are you in Norway by any chance? With 230 V line-line voltage and one broken fuse you end up with ~130 V to ground.– winnyCommented Oct 22, 2019 at 16:01
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Is your system 3-phase "Wye" or "Delta" (do you have a neutral)? Do you have any 3-phase loads?– Harper - Reinstate MonicaCommented Oct 22, 2019 at 16:25
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2 Answers
The fuse is designed to protect from overload, not render the circuit safe for maintenance. When a circuit is protected by 2 fuses, you need to pull both fuses. This would also be true, for instance, in a North American or Philippine 240V load.
This problem is precisely why North America has moved to circuit breakers, and installations like this use multi-pole breakers that either have "common trip" across all poles, or are handle-tied for "common maintenance shutoff" across all poles.
answered Oct 22, 2019 at 16:29
Harper - Reinstate MonicaHarper - Reinstate Monica
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For a three phase system, your measured voltages are correct. So it sounds like in your lighting circuit all three phases are being used, but you only expect two to be used. Probably the easiest to start to find the third leg, would be to turn off the other fuses/breakers, until you find the one that turns off the lights. Then if you are up for it, change your wiring.
Although this might have been done initially to keep a balanced load across all three phases, which is important. So use caution when changing your loads around.
