- Three phases Electrical Installation In the old Office complex, it has Suddey increase voltage and burns lamp and ceiling fan & other equipment how it can happen ?
sounds like it is probably a loss of neutral, or perhaps a high resistance neutral due to corrosion or break at any point before the 3 phases are split. When this happens, unless the 3 groups of loads are in perfect balance, they will no longer getting 230V each but instead share the 400V phase to phase voltage very unequally. so perhaps 1/3 of the building gets 100V and the other 2/3 get more like 300V ....
And also anything connected neutral /earth potential may suddenly rise to a hazardous voltage - and the conditions are often unstable as once things fail due to overovltage the stresses on other parts of the network increase and the voltage unbalance shifts. It can be very pretty to obserrve as lights brighten, then dim then fail but this is a potentially very dangeous fault and may be in the building or in the supply cables and transformer outside. Isolate everything, get out of the building and get it checked without delay.
Mike
What is is the nominal or declared voltage, what voltage is typically supplied, and to what voltage was it increased ?
A modest increase to the upper limit of the permitted range, will have to be accepted.
A more serious increase is likely the result of an open or high resistance neutral connection, this will reduce the voltage on ther highest loaded phases and increase the voltage on the lowest loaded phases.
If this defective neutral connection is within the customers installation, then the customers electrician will need to rectify it.
If the defect is in the power companies equipment, then they should rectify it.
Various faults in the power companies equipment can result in higher voltage than normal, but an open or high resistance neutral is by far the most common.
,This is an old story. It's been more than 30 years since I received an emergency call and responded by telling them to turn off the main switch. I went to check the breakdown right away and turned off the old 200 AMP main switch. I checked the incoming voltage with a test lamp but there was no blinking or brightness. I then reduced the load and turned on the power again by forcing it with a screwdriver without closing the cover handle. I could then see the sparking in link neutral in the coming terminal and the outgoing terminal. ..it can be very dangerous to use of high loads when it using single phase motors, Ac, etc
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