irregular voltage question.

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vermathrax

Member
Location
florida
I am a Meter Tech and I was doing a voltage check on a single phase 120/240 socket. I was getting 120v phase to ground and phase to neutral on both legs. I was only getting 6.5 volts phase to phase. I checked the house next door to the one I was working on and had good voltage on all tests.Both houses come from the same drop pole and the same transformer. Any ideas on what could cause this? I though at first it was an open neutral but that is not the case with me getting good readings phase to neutral. Any help would be greatly appreciated.

While I wont be the one going back to fix the job I would like to know just for my own knowledge. Thank you.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
150306-1708 EST

My guess is that both of your phases are actually the same phase, or one of the hot lines is open at both ends.

You did not mention whether the meter was pulled before the voltage measurements.

Suppose the meter was pulled, the readings were what you measured, a high impedance meter was used, and one of the hot lines was open at or near the transformer. In this case capacitive coupling from the good phase to the isolated phase might produce your readings. The 9.5 V difference looks large other than for an isolated wire. Put a 100 W incandescent light from the lower voltage phase to neutral. Does the voltage drop way down?

Both 120 V readings should not be the same with 9.5 V difference between the two hot lines

More later if someone else doesn't cover the other situations.

.
 

coop3339

Senior Member
Location
NJ
One of the legs is open between the transformer and meter socket. You are reading the voltage trough the 240v loads.
 

coop3339

Senior Member
Location
NJ
or if the meter is out when you are reading this it could be capacitive coupling. But in either case its likely you have a bad splice between where you are testing and the transformer. Maybe try a low impedance meter.
 

vermathrax

Member
Location
florida
150306-1708 EST

My guess is that both of your phases are actually the same phase, or one of the hot lines is open at both ends.

You did not mention whether the meter was pulled before the voltage measurements.

Suppose the meter was pulled, the readings were what you measured, a high impedance meter was used, and one of the hot lines was open at or near the transformer. In this case capacitive coupling from the good phase to the isolated phase might produce your readings. The 9.5 V difference looks large other than for an isolated wire. Put a 100 W incandescent light from the lower voltage phase to neutral. Does the voltage drop way down?

Both 120 V readings should not be the same with 9.5 V difference between the two hot lines

More later if someone else doesn't cover the other situations.

.


There were 2 tests done, one with the meter in the socket, and one with it removed. Both tests had the same results. The house had power going to it and had lights on in the house at the time of the tests. It was an existing service and was having no other issues before being cut for non payment. When it was reconnected was when we found this problem. We were using a FLUKE multi-meter to test it on the reconnect. I have seen this problem with an open neutral but never when getting 120v on both legs. I would use the incandescent test but I will not be returning to the service until after it has been fixed by an electrician. I was an electrician before becoming a Tech so I was miffed at not getting the problem resolved on my own.
 

vermathrax

Member
Location
florida
or if the meter is out when you are reading this it could be capacitive coupling. But in either case its likely you have a bad splice between where you are testing and the transformer. Maybe try a low impedance meter.


I thought about the bad splice but wasn't sure if that would cause a complete 120v on BOTH legs. But the fact that I did both tests, one with the meter in, and one with it out ,and had the same readings was confusing.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
150306-2349 EST

vermathrax:

The comments by coop3339 probably apply, but make more accurate measurements under steady-state conditions. Resolve voltage to 0.1 V, but visually average as seems appropriate when power company voltage seems stable. The 9.5 V difference is confusing if the other readings were both 120.0 with and without the power company meter installed.

Use a 1500 W small heater inside the home because it will be a better test load when the power company meter is installed, and 25 to 100 W bulb outside when the meter is removed from its socket.

.
 

kwired

Electron manager
Location
NE Nebraska
There were 2 tests done, one with the meter in the socket, and one with it removed. Both tests had the same results. The house had power going to it and had lights on in the house at the time of the tests. It was an existing service and was having no other issues before being cut for non payment. When it was reconnected was when we found this problem. We were using a FLUKE multi-meter to test it on the reconnect. I have seen this problem with an open neutral but never when getting 120v on both legs. I would use the incandescent test but I will not be returning to the service until after it has been fixed by an electrician. I was an electrician before becoming a Tech so I was miffed at not getting the problem resolved on my own.

May not be anything on the load side of the meter for an electrician to fix, if it is what most of us think it is you have lost one of the ungrounded conductors somewhere ahead of the meter.

Apply line to neutral loads to each side but not equal loads. Can be just a 40 watt light bulb and a 60 watt light bulb, but 1000 to 1500 watt heaters are my preference for test load for finding bad connections. If incoming lines are in good condition you will have (near) balanced voltage to neutral and (nominal)240 volts line to line less some voltage drop depending on load, conductor length, size etc.

Testing without load can give you false sense of things being within tolerances because with no current flow you have no voltage drop over bad connections.
 

meternerd

Senior Member
Location
Athol, ID
Occupation
retired water & electric utility electrician, meter/relay tech
Use a Beast of Burden. It will tell you immediately if it's a service problem. If you don't have one as a tech, get one. Saves a lot of confusion and is simple to use.
 
Location
MA
You either have an open on one high side and are reading 120 on the dead side because it's backfeeding through load in the house or two high sides are either burned together or someone screwed up and put the two high sides from the service on the same high side on the main cable. Since they didn't report a problem, I would be it's the latter. If they have no 240 load they will not notice any problems. Could be that they are part off and didn't report anything, but not likely. Also, like others have mentioned, if the main is off, it doesn't matter if the meter is in or not when you're taking readings. It's likely that they shut their main off because they were being restored and were told to do so before you came out by collections, in which case it wouldn't be likely that you would be getting backfeed through load.

My best guess it the two high sides are connected somewhere by fault or by accident. Although, there is a chance that the service became part off while they were shut off so they would not notice a problem until after you left.
 

kwired

Electron manager
Location
NE Nebraska
It's likely that they shut their main off because they were being restored and were told to do so before you came out by collections, in which case it wouldn't be likely that you would be getting backfeed through load.
I bet customer shutting the main off when requested happens often on those disconnect for non payment situations:happyno::happyno:

Unless maybe the POCO refuses to install a meter under load and will leave without installing it - but they have no problem disconnecting under load for non payment reasons:ashamed1:.
 
Location
MA
I bet customer shutting the main off when requested happens often on those disconnect for non payment situations:happyno::happyno:

Unless maybe the POCO refuses to install a meter under load and will leave without installing it - but they have no problem disconnecting under load for non payment reasons:ashamed1:.

That's exactly what the POCOs do and people believe them, I know it makes zero sense. They say they won't restore unless there is someone home with the breaker off and people almost always comply. I would never drive out and not restore someone because of that. It's a serious waste of time and makes no sense. We restore people's power all the time without notifying them for regular power issues, but for non-payment it's different. I've never understood why or received a valid explaination why it's done, but a lot of companies make the threat of not restoring unless someone is home with the breaker off. Meter guys will not restore, but if payment comes after they go home, then troubleshooters go out and restore it whether someone is home or not.
 

meternerd

Senior Member
Location
Athol, ID
Occupation
retired water & electric utility electrician, meter/relay tech
That's exactly what the POCOs do and people believe them, I know it makes zero sense. They say they won't restore unless there is someone home with the breaker off and people almost always comply. I would never drive out and not restore someone because of that. It's a serious waste of time and makes no sense. We restore people's power all the time without notifying them for regular power issues, but for non-payment it's different. I've never understood why or received a valid explaination why it's done, but a lot of companies make the threat of not restoring unless someone is home with the breaker off. Meter guys will not restore, but if payment comes after they go home, then troubleshooters go out and restore it whether someone is home or not.
As a POCO, the reason we don't reconnect a service unless someone is home is: We often don't have access to the main breaker, so reconnecting a meter may or may not energize the load. If someone leaves a stove on with something on a burner or a heater on next to something flammable, it's a potential fire hazard and we would likely be liable. Since we are a community with many second homeowners, they will turn off their main when they leave and call us to turn it back on when they plan to return. We used to oblige to keep a good relationship with the customer, but reports from utilities about fires helped us decide to stop. Now we never reconnect unless the breaker is off. If we have no access to the breaker we won't reconnect. If the breaker is off, we will not turn it on. Has to be someone home. Yes, we do pull meters under load. Not a safety issue in our opinion. Face shield, secondary gloves and FR shirt are required.

We don't like to install meters under load because it may take a bit of maneuvering to get the jaws lined up and any momentary contact can produce sparks and possible load side voltage issues.
 
Last edited:
Location
MA
Yeah but also the power goes out unexpectedly all the time and we (I work for the POCO too) restore without notice. Emergency outages and natural outages are always restored without seeing if people are home... POCOs replace services and do emergency outages all the time when nobody is home. It's just a weird double standard is all that I'm saying. I guess the only real argument is picking up load with a meter, but like you said, nobody has a concern with dropping load with a meter.
 

kwired

Electron manager
Location
NE Nebraska
Yeah but also the power goes out unexpectedly all the time and we (I work for the POCO too) restore without notice. Emergency outages and natural outages are always restored without seeing if people are home... POCOs replace services and do emergency outages all the time when nobody is home. It's just a weird double standard is all that I'm saying. I guess the only real argument is picking up load with a meter, but like you said, nobody has a concern with dropping load with a meter.

I see a lot of that myself - especially after a widespread outage, if nobody is home when power comes back on and they left the range turned on..... it resumes unattended.
 

meternerd

Senior Member
Location
Athol, ID
Occupation
retired water & electric utility electrician, meter/relay tech
I agree, it sounds like a weird double standard, but....an unexpected outage due to whatever reason is almost never restored by dealing with the meter or service disconnect. It's usually a line crew reconnecting wire, replacing a fuse, etc. Disconnecting for non-pay involves pulling the meter, booting off the lower stabs and replacing the meter. A reconnect again involves pulling the meter, removing the boots and replacing the meter. Totally different animal.
 

kwired

Electron manager
Location
NE Nebraska
I agree, it sounds like a weird double standard, but....an unexpected outage due to whatever reason is almost never restored by dealing with the meter or service disconnect. It's usually a line crew reconnecting wire, replacing a fuse, etc. Disconnecting for non-pay involves pulling the meter, booting off the lower stabs and replacing the meter. A reconnect again involves pulling the meter, removing the boots and replacing the meter. Totally different animal.

Outages around these parts due to wind or ice damages often involve replacing meter sockets, masts, service drops, point of attachment, because any or all of those mentioned components got ripped off the side of the building or at least severely damaged when (usually) a tree branch falls on the service drop. Of course when drop to a specific customer is ripped down an EC is usually involved with putting it back together, but sometimes there are customers that have no damage on their premises or their drop, but are still out because of downed lines elsewhere. They are not notified when power is to be restored, it just comes on when ready, so if something were left on from the time power went out or even switched on while power was out - it will start and will not care if someone is there to tend to it or not.
 
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