Lighting Flicker

[ptonsparky]

Be interested to see what they are doing for a line side EG.

Don't ski. To old, but I like road trips. Sounds like a spring time job anyway.

 

[cdcengineer]

I would think some damage might have occurred to some appliances/utilization equipment, but I have no idea how to test for it and then prove it to XCEL.

 

[gar]

110111-1545 EST

cdcengineer:

Does anything smell burned? Are any devices not operating properly? Especially older electronic units. Heaters, flat irons, and stove elements if not subjected to excess voltage for too long are probably undamaged. Electronics in any any of these devices might be. Check electronic furnace controls, dimmers, clocks, burned out light bulbs, outlet strips with MOVs, computers, monitors, transformers (check your door bell), whole house transient limiter (probably an MOV), and etc.

Some failures might not occur immediately.

This whole house auto-transformer thing might be a good protection device for homes.

Why does everyone almost always assume a neutral problem with light flicker with no additional information. Isn't it a 1/3 probability until additional information is available? Is there something special about neutrals that they are more prone to fail? Do groundhogs like neutral wires more than hot wires?

.

 

[hurk27]

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.

I agree our utility uses these all the time, if a lost neutral happens they wire it 240 in 240/120 out, if a hot is lost, they wire it 120 in 240/120 out and tell you not to run heavy loads till lateral is fixed, nothing more then a dual winding 1 to 1 transformer on both primary and secondary, H1, H2, H3, H4 in, and X1, X2, X3, X4 out, usually a 10 kva but I have seen them use a 15 kva also.

Here they have an adapter that plugs into the meter socket and a clamp to the box to tie in the neutral, yea I know what the POCO's get away with.

 

[LarryFine]

Why does everyone almost always assume a neutral problem with light flicker with no additional information.

Because, as in this instance, the only way the voltage can rise on one line while dropping on the other is with a neutral-conductor resistance.

A problem in one of the line conductors would result in a voltage-to-neutral drop on one line without a corresponding voltage rise on the other.

 

[LarryFine]

... if a lost neutral happens they wire it 240 in 240/120 out, if a hot is lost, they wire it 120 in 240/120 out and tell you not to run heavy loads till lateral is fixed, nothing more then a dual winding 1 to 1 transformer on both primary and secondary, ...

Wouldn't a single, center-tapped winding (basically an auto-transformer, as Gar suggested), do the same thing in both cases?

 

[gar]

110111-2355 EST

Larry:

My qualified sentence excluded information that there was a voltage shift of the neutral.

Usually the question is presented that there is a light flicker, and no other information is initially provided. Then all sorts of questions have to be asked to get some useful information. But without more information the pat answer seems to be it is a neutral problem.

Maybe neutrals are more likely to fail for some reason. I don't know.

.

 

[LarryFine]

Usually the question is presented that there is a light flicker, and no other information is initially provided. Then all sorts of questions have to be asked to get some useful information. But without more information the pat answer seems to be it is a neutral problem.

I think it's because we usually suggest measuring line-to-neutral voltages as an early test, and/or whether the flickering includes brightening as well as dimming.

(Relative to normal, that is. Of course, flickering includes brightening and dimming. )

 

[hurk27]

Wouldn't a single, center-tapped winding (basically an auto-transformer, as Gar suggested), do the same thing in both cases?

sure, just not seen them used for this around here, not sure how common they would be, I know zig zags are used at higher voltages but at 240/120?, I have a 10kva 1 to 1 I use for trailer parks when we loose a underground leg or neutral, to get by till we can get the repair done, especially when the ground is frozen.

 

[hurk27]

110111-2355 EST

Larry:

My qualified sentence excluded information that there was a voltage shift of the neutral.

Usually the question is presented that there is a light flicker, and no other information is initially provided. Then all sorts of questions have to be asked to get some useful information. But without more information the pat answer seems to be it is a neutral problem.

Maybe neutrals are more likely to fail for some reason. I don't know.

.

Actully you were the first to point out the neutral problem in this thread in post 3, but I think the reason we tend to lean toward the neutral as being a problem is the fear of the damage it can cause?

 

[gobblerhuntr]

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.

Glad to hear it is on the utility side underground, I suspected that in an earlier post. It is more than likely in the neutral, but they should be able to take a fault locator and find it pretty easy. We use a Metrotech with very good luck. And the device they put at the house has been described here already. I know the Von company that makes our "thumper" makes a device like this that aides utilities when they have a bad underground. It rolls around on wheels and you hook it up at the meter base to buy some time until you get the underground fixed. Most of the time we lay a temporary wire on the ground to get through the night and come back and fix it in the daylight.

 

[ggunn]

I agree that it sounds like a problem with the neutral, but aren't most series type problems with conductors at the connection points rather than at some point in the cable itself? The only thing I can think of that would introduce a significant series resistance somewhere in the middle of the neutral line would be a partial/near severance of the buried wire. How likely is that?

 

[ActionDave]

Very likely in my area if it is not in conduit.

 

[ptonsparky]

I agree that it sounds like a problem with the neutral, but aren't most series type problems with conductors at the connection points rather than at some point in the cable itself? The only thing I can think of that would introduce a significant series resistance somewhere in the middle of the neutral line would be a partial/near severance of the buried wire. How likely is that?

Reason I bought a fault locator years ago. More than paid for itself.

 

[gar]

110113-1109 EST

ActionDave:

What is the cause, and is it unique to the neutral?

Why does conduit eliminate the problem?

Years ago I was in Boulder and loved it. Spent June to December of 1950 there. This was when the flat plains started on the east side of the University, and there was a riding stable close by. In the summer I was in a dorm adjacent to a road running north and south. East of the road was just open land as far as you could see. On Friday nights the stable had a steak fry up in the park, and we rode horseback up and back down. From a Google photo it looks like this is called Boulder Mountain Park. The satellite photo seems to have a cloud in the this area. I also climbed in that area and took some interesting photos.

.

 

[hurk27]

110113-1109 EST

ActionDave:

What is the cause, and is it unique to the neutral?

Why does conduit eliminate the problem?

I know here it's kind of rare for neutral fails, we do get them but not as much as line fails, most are damaged when the utility knifed the laterals in and skinned the neutral exposing the conductor, some very rare are ground boring rodents that can chew into the insulation, while a hot conductor can burn off in a matter of weeks, a neutral will depend upon how much voltage drop it has, and can take as long as a few years, the last one I ran into took a year and 3 months from the point the utility put it in the ground, we took photo's for the home owner to document it was an installation problem that caused the damage so the utility had to replace the electronics that was damaged.

As far as conduit goes, about the only thing it will protect against is the rodents and hand shovels.:roll:

 

[ggunn]

I know here it's kind of rare for neutral fails, we do get them but not as much as line fails, most are damaged when the utility knifed the laterals in and skinned the neutral exposing the conductor, some very rare are ground boring rodents that can chew into the insulation, while a hot conductor can burn off in a matter of weeks, a neutral will depend upon how much voltage drop it has, and can take as long as a few years, the last one I ran into took a year and 3 months from the point the utility put it in the ground, we took photo's for the home owner to document it was an installation problem that caused the damage so the utility had to replace the electronics that was damaged.

As far as conduit goes, about the only thing it will protect against is the rodents and hand shovels.:roll:

In a related story...

I was working on a job that involved a 250' run of 4/0 cable in conduit. The landowner decided to fence around the remote facility we were working on. Even though the filled in trench from the cable run was very obvious and there were signs posted, guess where the fencing company decided to sink a fence post.

 

[hurk27]

In a related story...

I was working on a job that involved a 250' run of 4/0 cable in conduit. The landowner decided to fence around the remote facility we were working on. Even though the filled in trench from the cable run was very obvious and there were signs posted, guess where the fencing company decided to sink a fence post.

Oh course in the easier to dig pre dug dirt!!:roll:

 

[ActionDave]

110113-1109 EST

ActionDave:

What is the cause, and is it unique to the neutral?

Why does conduit eliminate the problem?

I was addressing the issue of harmed connections vs. harmed conductors that ggun asked about irrespective of their use.

Just like ptonsparky our shop purchased a fault finder and it has been a good investment. Most of the time it is the hot that is burned in two, but not always.

Years ago I was in Boulder and loved it. Spent June to December of 1950 there.

That would have been a fantastic time to be there. Boulder is quite a bit bigger now, but the vistas are still fantastic.
I'm in the southwest corner of the state. The mountains are just as beautiful and the winters are not near as harsh.

 

[tryinghard]

Oh course in the easier to dig pre dug dirt!!:roll:

How much a foot?