pulsing lights

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spyder

Member
Location
Massachusetts
Went on a service call for intermitent flickering lights today at a large residence. My first thought was loose neutral or connection. All connections checkout okay.

Of course the power quality showed not signs of trouble until I was ready to leave and the lights began to evenly pulse (not really what I would call flicker for about 30 seconds).

The house is feed underground from a pad mount vault type transfromer. This transformer feeds no other houses. My feeling is the problem lies with the transformer.

Has anyone ever encountered a similar problem or pulsing lights (not flickering or brown out)?
 

bphgravity

Senior Member
Location
Florida
Re: pulsing lights

This sounds like it may possibly be a voltage drop issue from a large load like a compressor that is failing or having a hard time starting. Turn off all loads except for lighting and turn on one appliance at a time. You may be able to narrow it down to one circuit or one particular peice of equipment that is effecting house power quality. Just a couple ideas that may help? :confused:
 

spyder

Member
Location
Massachusetts
Re: pulsing lights

I heard mention of them having problems with one of the well pumps. I never considered that it may effect the house voltage. Thanks for the help.
 

spyder

Member
Location
Massachusetts
Re: pulsing lights

From the poco:

Set our voltage recorder at the transfromer from 4/22/03 at 13:45 to 4/28/03 at 11:20.
There were several instances where the voltage went up to 125.9 volts for durations ranging from one to ten cycles.
There was one drop in voltage on 4/27/03 at 07:22 for one cycle when the voltage dipped to 110.9 volts.

Anyone have any thoughts? The source voltage was reported to be very stable, thus ruling out a bad transformer.
 

bennie

Esteemed Member
Re: pulsing lights

The high voltage appears to be from load dumping.

The voltage sag appears to be a fault on the primary side such as an insulator flashover.

These events would be hard to detect by visual observation.
 

bennie

Esteemed Member
Re: pulsing lights

An overvoltage on the secondary, with an increase in current, is caused by load shedding on the primary.

An overvoltage on the secondary, with a decrease in current, is caused by load shedding on the secondary.

[ April 29, 2003, 07:42 PM: Message edited by: bennie ]
 
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