Lighting Flicker

[gobblerhuntr]

110108-1651 EST

If the voltages are good at the meter of the house in question under the load test, then the neighbor has nothing to do with the problem.

On the other hand if the neighbor is willing to let someone into their home, then that neighbor can be useful. If the problem is inside the transformer, at its terminal, or in a neutral connection common to both houses, then a load change producing a large unbalanced voltage at home A resulting from a problem closer to the transformer than the common neutral connection point for the two houses will also produce a large voltage change at house B.


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Correct, then once determined if the problem is in the house or on the exterior you make your next move from there. If inside, you have to start running your circuits for problems. You might consider checking amps on each leg to make sure it is not drastically overloaded, which I doubt unless you have added something significant. If on the outside I would calmly go and talk to the POCO and tell them what you have done and ask if they could come out and check once again, also mention that you neighbor is off the same pot and you wish they could disconnect him long enough to check and see if he was effecting (sp) you.

One other thing I have seen in the past would be a bad leg on the underground service. One that has not completely failed but will soon. this could cause the normal voltage with no load and weird when load was applied. With the voltage readings I would think it was in the neutral somewhere.

 

[cdcengineer]

OK and...

I might have missed where they broke the meter seal!

If they passed this load side test on the OP's house, could it still be the neighbors service that failing due to neurtal (ground) tied at the transformer.

It'd be intresting to read the voltage at the neighbor's panel and meter as well...

The POCO need to come and meggar thier circuits,(if both houses fail) if they balk, notify chief POCO engineer, then up the pecking order...

I have broken the meter seal after I called the utility. Not many tests done this weekend as it's been dumping snow and now it's -12F.

 

[cdcengineer]

Also, neighbor let us shut off his main and we still had the flicker. The search continues. Will try Huck's test once things warm up.

 

[ptonsparky]

I have broken the meter seal after I called the utility. Not many tests done this weekend as it's been dumping snow and now it's -12F.

I am lucky then, snow, 14 degrees and I get to go change out a 40 hp pump motor. Snow drift is only a couple feet in the area so not bad.

 

[cdcengineer]

An answer to an old post - yes, there is a well pump and lift station. Neither of these need to be on to cause the flicker.

Summary of limited findings:

Using a 120V toaster as my trigger. Pre trigger measurements at either the main breaker, meter (line side - yes I cut the seal) or any receptacle.
A - 123V
B - 124V

Plug trigger into any recep. on A phase:
A - 108V
B - 136V

Essentially the same (only reversed) when plugged into a B phase receptacle. I didn't run this test with the neighbor's house as he lives out of town and let me shut off his main from the exterior. We do not know if he is experiencing any flicker. Gar's comments about the neighbor made me think we had the problem, because it was the neighbor who lives next to the XFMR and reported a buzz or hum in the first place. Shortly thereafter my problems started. The neighbor also lives right next to the pole/XFMR. He added over 100' of roof de-ice (heat tape) which sucks a ton of power. When his service was disconnected, I still had the flicker.

I'm thinking it's the XFMR is on it's way out. Anyone got comments? I will run further tests with a roll of #10 AWG as described above once the temps reach positive territory. And Tom, I would be outside working if it was a paying job, but the cobbler's kids never have any shoes - hah.

Thx

 

[LarryFine]

Pre trigger measurements at ... meter (line side)
A - 123V
B - 124V

Plug trigger into any recep. on A phase:
A - 108V
B - 136V

Essentially the same (only reversed) when plugged into a B phase receptacle.

If these imbalances are measurable at the line-side meter terminals, then the problem is on the utility side of that point.

That's the only test you need. You're done. It's the utility's problem, unless you're responsible for the lateral.

 

[cdcengineer]

Larry,

When measuring on the line side of the meter (with the meter installed), I'm still measuring the load. It's the load that causes the imbalance - granted this could be a result of a utility issue (which is what I'm betting on). Therefore, theoretically, couldn't it be a problem on my side?

 

[kingpb]

Can you pull your meter, and hook up an engine generator temporarily to your house and see if it still does it?

At least you'd know which direction, so to speak, you need to look.

I haven't seen in any posts where it was verified that the conductors run from the transformer to the house MDP were checked to see if they were sized properly. The situation you are having could very well be voltage drop related if the conductors are undersized.

Also, I wouldn't get to wound around the axle on how it was before, or not, or what was added etc. That may be a good starting point but if it doesn't pan out you can end up leading yourself astray.

Stick with what you know, and test for what you don't, form your conclusions on fact.

 

[gar]

110110-1501 EST

cdcengineer:

See photo p3 at my website http://beta-a2.com/misc_TMP_photos.html

There are three wires from the transformer posts that are about 5 ft long. At the ends of these wires are terminated my drop, my neighbors drop, and the ground wire to the pole ground rod.

You clearly have a neutral problem based on the low voltage moving with your toaster load from one phase to the other.

If your wiring from your transformer is similar to mine, then

1. If the bad connection is inside the transformer, or just on the outside where the single wire connects to the transformer post, then your neighbor and you will both see the same kind of voltage variation from a similar load at either house. If you turn the neighbor's power on and he has an outdoor outlet, then if the problem is common, then plugging your toaster in his outside outlet should produce the voltage change at your house. Also if you had a meter plugged into the same outlet at his house you would see the voltage change there.

Back to a load change in your house. Measuring the voltage from the transformer ground rod to your house main panel neutral or your house ground rod should not show much voltage change with and without the toaster load in your house.

If you are fairly sure of good continuity of an EGC from some outside outlet to your main panel neutral and ground rod, then you can easily get the house ground reference from an extension cord plugged into said outlet.


2. At the point near the transformer where the two neutrals, yours and your neighbor's, and probably the transformer ground rod wire are attached, is a good connection, then the neutral problem would be between this point and the neutral bar in your house. Then your toaster load would produce a large voltage drop between the transformer ground rod and your main panel neutral.

.

 

[cdcengineer]

Gar

The connections to the xfmr are a bit different. My underground are connected directly to the one terminal. There is an overhead which comes from the same stab-on point for the neighbors house but his connections live under their own lug.

I tested his voltage with and w/o the toaster on in my house. No change. I have yet to lug the toaster over just to see if the xfmr might be the problem. Might look funny crossing the street with a toaster.

Looked for a ground connection at the pole. Buried under 3 - 4' of snow at the moment. I like the idea of connecting the house to a generator. Will try and borrow one from my brother if it comes down to it.

 

[LarryFine]

When measuring on the line side of the meter (with the meter installed), I'm still measuring the load.

No, you're measuring two voltages that should be equal. The load is being used to cause the imbalance so you can find the point along the service where the imbalance suddenly disappears (if working toward the supply.)

Ignore the meter, other than the fact that it's one of several access points along the pathway. The line-to-neutral measurements should be the same on either side of the meter. You're only interested in the neutral.

In the meter, check the incoming neutral wire itself, not the terminal, to each line. If the imbalance is there, the resistance must be farther upstream. Otherwise, it's in the meter. Check each point (wire, terminal, etc.)

It's the load that causes the imbalance - granted this could be a result of a utility issue (which is what I'm betting on). Therefore, theoretically, couldn't it be a problem on my side?

The load causes the imbalance, which enables you to find the cause. Again, the cause must be on the line side of the farthest-upstream point you can access and still measure the imbalanced voltages.

If you get on the utility side of the resistance, the imbalance will vanish. Then, you can measure across each junction in the neutral pathway, where you'll find the missing ( (136-108)/2 ) 14 volts.

 

[gar]

110110-1855 EST

cdcengineer:

Did you work for Control Data?

If the toaster load in your house makes no difference at your neighbor's house, then the pole or pad transformer is OK.

Can you more clearly define what the neutral connections look like at the transformer. As I understand your comments there are separate lugs on the transformer terminal for your neutral and your neighbor's. Is that correct? Is the transformer on a pole or a pad? Does this also mean a separate lug for the wire, GEC, to the transformer ground rod?

.

 

[cdcengineer]

Larry - thanks for the input.

Gar - no I don't work for Control Data. Clear Design Consulting.

As for the xfmr and it's connections. It's a pole mounted - looks like a 50kVA. There are three "ears" (A, B, N) with two bolt connections. One bolt for my lateral, and one for my neighbor. I took a photo, but the forum won't let me upload. My house is fed underground and my neighbor's is overhead. My lateral comes down the pole under a protective covering 1/2 conduit. As for pole grounding, I can't tell what we have. The utility is coming back tomorrow to discuss the tests we've run. They're starting to think it's a problem with the lateral. I hope not because my yard has been dug up enough.

As for the earlier post regarding voltage drop.... it's not likely as my connected load is not very large (110A) on a 150A, 1-phase 120/240V service fed from #2/0 AL. I'll post the findings following tomorrow's meeting.

I used to drive a service truck and dealt with troubleshooting on a daily basis (nearly 10 years ago). It was only two years of electrical service. I am by no means, an "old salt". I spent more time in new construction, but left that for a desk job. I have seen similar problems to this and they were always neutral related. I really appreciate all the advice. Thanks to all for the constructive insight and recommendations. This is a great resource.

 

[gar]

110110-2226 EST

cdcengineer:

If the GEC is well connected at the transformer neutral, then it provides a very good test lead to the transformer center tap.

If actually using contact with the neutral supply wire, meaning the probe touches the wire and not the lug, entering the meter shows this unbalanced voltage under load, then the problem is toward the pole transformer. Thus, it is either at the connection to the transformer or somewhere between there and the meter.

If there is an actual high resistance in your underground neutral wire, then, if possible, some non-destructive means should be used to find the location. Destructive here means digging up your yard.

How or why would there be a high resistance within the neutral underground wire. Mine has been in the ground for 45 years with no problem. Admittedly it is 0000 copper 3 feet underground.

.

 

[Finite10]

"2. Many loads have 'inrush current,' and draw lots more current when they are first turned on; on startup they will cause significant voltage drop in the supply."

My thoughts are #2 here. My central air furnace w/ heat pump did this. Inrush I is the black hole of power on a little res service. Neutrals were tight, etc. on mine.

What loads coming on cause the flicker? Motor, fan, heat pump, well as mentioned, sump, freezer, refrig (compressor)...?

 

[gar]

110110-2334 EST

Finite10:

I think with all the evidence provided that the major problem is quite clearly high resistance relatively to what it should be in the neutral. The major question is where is the problem.

Inrush on some loads under normal conditions will produce light flicker. No question about that. In homes these are typically motor loads.

When you use something like a toaster or 1500 watt heater for a test load, ball park 12 A load, there is no appreciable inrush, and you get a large unbalanced pair of voltage readings each phase to neutral, and steady-state with the load, then you have a severe neutral problem. 28 V difference or 14 V unbalance, then the neutral has a resistance in the ballpark of 14/12 = 1.2 ohms. Way high.

With the evidence presented you do not blame this problem on inrush.

.

 

[ptonsparky]

What causes underground to go bad. Gophers, mice, fence posts, new septic systems, trees. That little Nick in the insulation during installation. A rock finally wore thru. No bushings on raceway. Look for the most recent change in the yard.

My locator will work in the snow.

 

[cdcengineer]

Pton - Gar,

Thanks for the follow-up. Pton - you just want to come to the mtns here in Colorado for some skiing ehh? I don't know if I can afford to fly you here for some locate work. Maybe XCEL would be willing though?

XCEL came by this morning. They happened to measure when things were at their worst (that I've seen). 148V - A, 103 - B

Anyway, they test and checked connections at the pole. It appears that the problem is between the pole and the meter (in the lateral). They've placed a device they referred to as "add-a-phase". I haven't had a chance to look at it yet as I'm on a two-hour conference call. It must be capable of deriving a neutral. They tell me their locate won't work in the permafrost here at 9,950' above sea level.

Thanks for all the input.

 

[gar]

110111-1356 EST

cdcengineer:

My guess is that the device is a center tapped auto-transformer at your house beyond the bad neutral point.

With voltage that unbalanced check that you do not have any damaged equipment. 148 V is rather excessive for a lot of devices.

.

 

[qcroanoke]

Pton - Gar,

Thanks for the follow-up. Pton - you just want to come to the mtns here in Colorado for some skiing ehh? I don't know if I can afford to fly you here for some locate work. Maybe XCEL would be willing though?

XCEL came by this morning. They happened to measure when things were at their worst (that I've seen). 148V - A, 103 - B

Anyway, they test and checked connections at the pole. It appears that the problem is between the pole and the meter (in the lateral). They've placed a device they referred to as "add-a-phase". I haven't had a chance to look at it yet as I'm on a two-hour conference call. It must be capable of deriving a neutral. They tell me their locate won't work in the permafrost here at 9,950' above sea level.

Thanks for all the input.

I think that is pretty much a transformer that will take what you have left and output 120/240 on the secondary until they can find your problem and fix it, which sounds like it may be a while yet.