Traveling voltage?

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DR MATT

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Mount Airy MD USA
This is an email from a friend that lives on Amelia Island in a residence (built 2006). He called with voltage of 135-145 at his receptacles. Shorted his vacuum, computers, & TV. Tried replacing wiring (new HR from panel to receptacles in bedroom) after removing all wiring from panel. Only one circuit, new breaker, new receptacles. We've been talking for weeks trying different things. By chance he was reading voltage at receptacles when the 1st street light went on the voltage SLOWLY decreased, then the 2nd street light came on and voltage slowly returned to 120. In the AM when the street lights came on (one at a time) the voltage (high) came back slowly. The power co has replaced the transformer, the service drop, a new main panel. My guess is the voltage is somehow back feeding through the fixture ballast? I am in Maryland and have not been to this house so I write emails and have the homeowner check different things. He has paid an electrical company over 4K and they could not figure out where the high voltage is coming from. this is the email I received this AM. VERY STRANGEWhen city street lights go on voltage is perfect to allreceptacles in house. When street lightsgo off, power is high and low on receptacles. Two lights on street.....one is 110 and the other s 220. One higher than the other. First light comes on sooner than the otherdue to the angle of the setting sun. When the first light goes on, voltage starts creeping out. When the second turns on all voltagedisappears. And vice versa in themorning when the lights go out.....voltage creeps back in until the secondlight goes off.

So what do you think?
 
Hmmm... seems like the "220" might be typo, perhaps meant 120.

Sounds like the POCO is using a autotransformer boost configuration to compensate for voltage drop. When the load drops the voltage goes up, and vice-versa.

Or perhaps a very marginally rated isolation transformer.

If one L-N voltage where high while the other low, I'd say a bad neutral connection somewhere.
 
Just about has to be a bad neutral someplace, most likely on POCO equipment if these street lights are connected to POCO side of customers service.

Someone needs to troubleshoot it and not just throw parts at it until it works.

Put a somewhat heavy load(hair dryer, space heater or anything in the 1000 - 1500 watt range) from one line to neutral. Measure voltatge from line to line, and each line to neutral both with the test load on and off. If your voltage from either line to neutral fluctuates more than a small percentage, as the load changes you have a neutral problem somewhere.


One more question - how long is the circuit length from POCO transformer to the service equipment, and what size are the conductors along this route? Excessively long conductors could cause enough voltage drop to cause similar problems. In that case larger conductors or moving the transformer closer is what needs to be done.
 
Neutral connection at the center tap of the transformer. Have seen the voltage as high as 300 before when a lug broke.
 
Hv&Lv said:
Neutral connection at the center tap of the transformer. Have seen the voltage as high as 300 before when a lug broke.
Click to expand...

I agree that it is a bad neutral connection some where, but 300 volts out of a 240 volt center tap winding? I'd like to hear this one:?


even with all the load between one leg and neutral the most you can get is 240 volts from the unloaded leg and neutral, as this only puts the voltage between the two hots of the winding?

If you get more then the 240 volts then the primary has a few turns shorted together thus lowering the turn ratio between the primary and secondary.

Since the OP stated the POCO has replaced the transformer, drop, service panel, the only thing I can see is are these loads fed from a sub panel or there multi-wire circuits? something with the neutral is being missed.

One time we had a problem where the X0 bushing was not bonded to the tank, and the POCO had bonded the drop neutral to the MGN and no bond from the X0 to the MGN only the tank was bonded to the MGN, it took getting their engineer out to make the line men understand the problem I was trying to tell them, the POCO ate about $6k in damages to electronics at that house.
 
hurk27 said:
I agree that it is a bad neutral connection some where, but 300 volts out of a 240 volt center tap winding? I'd like to hear this one:?


even with all the load between one leg and neutral the most you can get is 240 volts from the unloaded leg and neutral, as this only puts the voltage between the two hots of the winding?

If you get more then the 240 volts then the primary has a few turns shorted together thus lowering the turn ratio between the primary and secondary.

Since the OP stated the POCO has replaced the transformer, drop, service panel, the only thing I can see is are these loads fed from a sub panel or there multi-wire circuits? something with the neutral is being missed.

One time we had a problem where the X0 bushing was not bonded to the tank, and the POCO had bonded the drop neutral to the MGN and no bond from the X0 to the MGN only the tank was bonded to the MGN, it took getting their engineer out to make the line men understand the problem I was trying to tell them, the POCO ate about $6k in damages to electronics at that house.
Click to expand...

What is the voltage on the primary side with no neutral connection on a CSP XF?
 
Gentlemen, thanks for your great replies. The resident remove all wiring from panel and connect a 14-2 romex wire ran along the hallway from the panel with receptacles attached. Same problem. After that he added two ground rods attached #4 to meter and #4 to panel. All water piping in house is plastic. So no secondary ground. The problem only happens when these outside street lights go on. I keep telling him its the power co problem. He calls them out and they "don't find anything wrong" The electrical contractors in the area will not come out anymore because they cannot figure out what the problem is. I will copy and paste your comments so he can give them to the power co guys when they come out. The service drop is only 50' It is not a voltage drop problem. Service is 200amp. I'll let everyone know when and if they solve this thing. The resident told me to give his phone number (240-446-1703) Kim Davies. The poor guy is afraid to live in his house. Every time he comes back something else fries. He is afraid of a fire.
 
Hey there.. Been reading this forum for a while and thought this thread might be a good place to jump in. I am a troubleshooter for a POCO.

If you are testing high voltage on both high sides at the same time at the panel, then something is wrong on the outside and it's most likely at the transformer. Since they already changed it, I would say that it's either the station voltage or an autotransformer(regulator) like Smart $ said. Not all troubleshooters know what they are doing and it sound like the POCO is just replacing things without troubleshooting, which happens more than you think. You need to call them when the voltage is high-> have them test your transformer > if bad, test transformer on same phase > if it's still bad, test transformer on another phase > if good then they need to go to the next piece of equipment(either regulator, step down, or station transformer). When regulators, regulating step downs, regular step downs, and station regulation fails it always seems to step up in my experience. It may have gone to max raise and the only thing bringing voltage down is load, then it's spiking when load goes away.

Other people on the circuit may be experiencing the high voltage without them knowing as you may be the closest to the bad equipment. The voltage will start to regulate itself the further away you are. You might test 140 at your house and a few houses down will test 130 which is still high but not as noticeable.

Good luck. In the mean time, have them shut their breaker off. It sucks but so does losing your house.
 
Sounds like the POCO needs to send out a competent troubleshooter to me.

Even if it is not a POCO problem, a good troubleshooter will be able to find the problem, and if it ends up being on owners equipment, then he may still need to get an EC to come fix it.
 
130330-1353 EDT

First, someone with adequate safety knowledge needs to be doing the tests.

I suggest making a setup with two 15 or 25 W 120 or 130 V incandescent bulbs. One bulb is connected between neutral and phase A and the other bulb between neutral and phase B. These are to be powered from two circuits near the main panel with with no other load on the circuits.

If the neutral between the transformer and the point where the bulbs are connected to the neutral develops or has a high resistance compared to what it should be, then when trouble occurs one bulb should brighten and the other dim.

If both brighten or dim together, then the problem is before or in the transformer. Only other possibility is voltage fed into the street light circuits from something other than the 240 V center tapped pole transformer.

Use a Fluke 27 or equivalent for the following:

May be useful to measure the voltage drop between the pole transformer ground rod, directly on the rod, means digging into the earth a little, and the neutral in the main panel of the house.

But first measure between the pole ground rod and the pole ground wire.

Also measure the voltage from the home main panel neutral to a screwdriver at various points in the yard. I would like to see less than 0.5 V or thereabouts. If the voltage is higher than 0.5 V make sure you or the person making the measurements is properly insulated.

With what has been said so far it is very unpredictable what to expect for neutral to earth voltage. There might be some very large voltages.

Before doing anything else it would be useful to analyze how the street lights are wired to the transformer. Is there any other transformer around? For example, to supply a wild leg three phase.

.​
 
Still kinda fuzzy on what exactly they were testing. Were they only testing one circuit in the house or at the panel on both high sides? If they were reading 135/135 and 270 high side to high side then it's obviously not a neutral problem. There's no way to get that high of a voltage on a 120/240 service without something being wrong with a transformer or the station voltage. Can't really tell by what they tested if it's inside or out. If they're only testing one circuit in the house and not at the panel then it's pretty useless to replace all that stuff on both parties end without doing the right testing.

If it's that high for long enough for someone to get a Fluke and test it, then it should be easy for a decent trouble man to figure out. If it were me, I wouldn't leave the area until it was fixed. That type of voltage is too dangerous to homes to randomly fix things without being sure that the real problem is solved.

I would throw the street lights on the back burner or maybe rule them out all together assuming this is a normal residential neighborhood. I've actually had people call about street lights causing their lights to flicker. I only had one time where it was legit and it was because there was a shared high side connection between the lamp and the service. So technically it was the connector, not the lamp. People naturally turn their own lights on and off around the same time as street lights. They turn their lights on and when they start to flicker people see that the street lights came on and try to put two and two together but it doesn't add up. Also, the load on the system is changing in the morning and evening. That's what make me think you may have a regulator out of whack before the transformer that feeds the house, just a hunch though.

My best advice is to have them install a voltage recorder on the meter and document all the times they came out and the damage the voltage is causing. If it turns out that they neglected to fix the problem or it was their problem in the first place then file a claim. They tend to respond after you start filing claims. They really need to be shutting their main breaker off, preferably until it is fixed.
 
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