High current on neutral with a balanced load

[Eddie702]

I would check the current on the bare grounding electrode conductor. I probably goes from your panel to a metal water pipe....or could go the the well casing. Sounds like a bad neutral to me. If it is the neutral current will go back to the transformer via the GEC and earth

 

[gar]

201004-2202 EDT

jhardy13:

I want you to peruse many of my plots at http://beta-a2.com/EE-photos.html .
To a large extent I believe that the information I provide in a plot, and closely associated written material, provides a fairly good explanation of the experiment, and results.

Your plots generally don't provide adequate information, and I can't make head or tails from them.

You apparently have several different problems:
1. Damaged equipment.
2. Measurements that don't make obvious sense.
3. You don't really know what is connected to your main panel.
4. Some strange meaurement results.

I had thought you had one plot with a strange curve that had some possible 5 kHz wave for part of the cycle, wasn't large, and some other gyrations. I have searched twice for this, not found.

More later.

.

 

[oldsparky52]

Lights throughout our home burning out the same week they are installed even though they are rated for 130v, multiple PSUs acting erratically and needing replaced, and multiple electricians coming out to check all of our wiring and saying everything is up to code. This points to power quality issues. These problem started 4 years ago. I've lived in this home my whole life and this was not a problem before 4 years ago. I also find all of this very interesting and thought this would be a good place to get professional opinions and advice.

I also find this very interesting. I was a "construction" guy, so I did not get into theory a lot and never really used a scope, so you guys are playing above my education level.

In my uneducated mind, I don't see how having some minor DC voltages or a somewhat distorted wave form can cause lights to burn out, that seems more of over voltage issues that can easily be caused by a deteriorated neutral conductor. Your 50 amp one line load test seems to have ruled that out.

Have you ever been able to recreate the big neutral imbalance that you showed with the 3 meters in some of the early pictures, or is that a one time occurence?

Jhard13, please do not take this the wrong way, just like I'm hung up on a neutral issue somewhere (could be in the PoCo distribution lines) you seem to be hung up on wave forms. That seems to be your area of experience and you may be looking so hard at that, that you miss other signs.

In keeping with my tunnel vision, , how did you put that 50-amp 120-volt load on one phase? Curious, that's a pretty heavy load and I don't know how I could do that, or was that the PoCo doing it with their "beast" meter insert?

 

[ptonsparky]

IIRC, one of the moderators here has said “ If all you have is a hammer, everything is a nail.”
It works both ways.

This seems to be an overthought problem, but I do realize I have a small hammer.

 

[jhardy13]

I hope this isn't considered off topic because it could be related. I found something interesting. We have three TV cable boxes in our home on different circuits. Each of which is connected to the coax cables that run through our attic to the service entrance next to our meter. When I disconnect a coax cable from the back of one of these cable boxes, I get a large spark. I measured from the cable box connector to the coax cable shield and center pin and sure enough, there is 62 volts between them. I'm attaching a photo of this. It's not ghost voltage because it sparks when I touch the coax cable to the threads on the back of any of these boxes. When I unplug the cable boxes at the socket, the voltage goes away. When I disconnect the hdmi cable going from the cable box to the TV, the voltage drops from 62v to 52v. Does this tell you guys anything?

 

[oldsparky52]

Are the tv and cable boxes all 2-wire plugs or is one of them a grounded plug?

 

[jhardy13]

Are the tv and cable boxes all 2-wire plugs or is one of them a grounded plug?

They are all 2 wire plugs

 

[oldsparky52]

Time to call the cable TV company too.

 

[ptonsparky]

Time to call the cable TV company too.

oh those small details.

I hope this isn't considered off topic because it could be related. I found something interesting. We have three TV cable boxes in our home on different circuits. Each of which is connected to the coax cables that run through our attic to the service entrance next to our meter. When I disconnect a coax cable from the back of one of these cable boxes, I get a large spark. I measured from the cable box connector to the coax cable shield and center pin and sure enough, there is 62 volts between them. I'm attaching a photo of this. It's not ghost voltage because it sparks when I touch the coax cable to the threads on the back of any of these boxes. When I unplug the cable boxes at the socket, the voltage goes away. When I disconnect the hdmi cable going from the cable box to the TV, the voltage drops from 62v to 52v. Does this tell you guys anything?

Where are the scope images?

 

[Electricmo]

I wonder if someone in your neighborhood has a bad service neutral? Is your surrounding neighborhood fed by the same POCO? Sometimes there is joint use poles with 2 separate utilities using them. Possible someone has a bad water heater element.

 

[gar]

201005-2321 EDT

jhardy13:

Your failure to mention the cable TV connections left a big hole in your story. And this is possibly the source of one of your problems. But tests that were run possibly should have pointed in that direction.

Other comments :

In your post #172 are shown two plots. 20200902-205115 shows a curve with no added peak, and 205108 shows a centered pulse added at the peak of the base waveform. Assuming the base is close to the result of a resistive load, then that top pulse is not the result of a transformer. Furthermore, are there any transformer loads in the home? A transformer magnetizing current pulse appears at an excitation voltage zero crossing.

This pulse could be an MOV that has too low of a trigger point.

.

 

[ptonsparky]

Looking at your image in post 245.

You are not measuring voltage between cable shield and center pin in that picture. Your black lead is not on the shield.
It’s someplace else in the universe. IMO, you may as well have it attached to the cats tail.

We are now waiting for you to repeat your previous tests with all your cable connections removed. Add one cable box. Remove and test again with second. Repeat with third.

 

[oldsparky52]

Looking at your image in post 245.

You are not measuring voltage between cable shield and center pin in that picture. Your black lead is not on the shield.
It’s someplace else in the universe. IMO, you may as well have it attached to the cats tail.

We are now waiting for you to repeat your previous tests with all your cable connections removed. Add one cable box. Remove and test again with second. Repeat with third.

Good eye! I didn't look at that close enough. He's on the copper of the cable and the metal the shield would connect to on the box. I wonder if there is a voltage from the shield on the cable to the metal on the box connector.

 

[gar]

201006-2156 EDT

jhardy13:

Can you recreate the conditions where you measured a number of amperes on the neutral wire and had nearly balanced currents on the L1 and L2 phases? If so, then get plots of L1, L2, and N currents, and with a correlating L1 to N voltage plot. Display those.

Quit displaying pictures of your VOM which takes a million or so bytes of storage, and I can hardly read the displayed value anyway, and just type the value, which I can read, and only requires a few bytes of storage. For the most part the picture provides no useful information that can not be provided with only a small number of bytes.

When you can recreate the conditions with the unexpected high neutral current, then we can proceed to find the source,

.

 

[gar]

201007-1247 EDT

Interesting experiment in my backyard.

Test is rwo screwdrivers as test probes into the earth. Distance apart is 10 ft. Meter 4.5 digit RMS 10 microvolt resolution. Soil is clay loam somewhat moist.

I make N-S and E-W measurements. Several years ago I was possibly as high as 100 mV most of the time, and rarely peaking at 200 mV. This last Sunday I was at a peak N-S of 10 mV, and E-W of 4 mV. Today I am at about 4 mV both ways.

Ground path voltage is not jhardy13's problem.

Over a weeks period of sampling my water line current I was never over 300 mA, and usually around 200 mA.

,

 

[gar]

201009-1645 EDT

Reran my ground voltage experiment.

This is two probes 10 ft apart.

Middle of backyard. Both N-S and E-W about 4 mV. Consistent with previous post.

Front yard one probe very close or in contact with the pole transformer grounding rod at the pole base, and the other probe 10 ft away toward the meter box on side of house. Both my water pipe and AC power enter the house at about the same point. The water line runs away from the entry point about perpendicular to power ground path. Voltage about 140 mV.

.

 

[gar]

201009-1714 EDT

I believe there have been some comments on transformer magentizing current that are wrong.

Create a test circuit with AC power to a transformer. I used 120 V 60 Hz to a 175 VA transformer. This is a large enough load that I can use my Fluke Hall probe to measure current, and have DC isolation.

Use 2 mS/major div for horizontal sweep. Display the 120 V excitation voltage on one channel, and sync from this signal so the negative slope zero crossing occurs at mid screen. On a second scope channel display the transformer input current. The current waveform will be slightly offset from zero for a while, then has a large peaked rise. and fall centered at the voltage zero crossing. The next half cycle is a repeat, but of opposite polarity. What is important here is the phasing of the peak, 90 degree lag from the excitation voltage.

Next replace the transformer with a pure resistance. The current waveform is the same as the voltage, and there is no shifht of zero crossings.

.

 

[Hv&Lv]

I also find this very interesting. I was a "construction" guy, so I did not get into theory a lot and never really used a scope, so you guys are playing above my education level.

In my uneducated mind, I don't see how having some minor DC voltages or a somewhat distorted wave form can cause lights to burn out, that seems more of over voltage issues that can easily be caused by a deteriorated neutral conductor. Your 50 amp one line load test seems to have ruled that out.

Have you ever been able to recreate the big neutral imbalance that you showed with the 3 meters in some of the early pictures, or is that a one time occurence?

Jhard13, please do not take this the wrong way, just like I'm hung up on a neutral issue somewhere (could be in the PoCo distribution lines) you seem to be hung up on wave forms. That seems to be your area of experience and you may be looking so hard at that, that you miss other signs.

In keeping with my tunnel vision, , how did you put that 50-amp 120-volt load on one phase? Curious, that's a pretty heavy load and I don't know how I could do that, or was that the PoCo doing it with their "beast" meter insert?

The beast is a 20 amp machine

 

[gar]

201014-2146 EDT

No response from jhardy13:

jhardy13 can you repeat whatever conditions were present when you had relatively equal L1 and L2 currents, and a not near zero neutral current? Somehow try to repeat those conditions, and then remove all the cable connections. Does this change the neutral current to near zero?

.

 

[ptonsparky]

201014-2146 EDT

No response from jhardy13:

jhardy13 can you repeat whatever conditions were present when you had relatively equal L1 and L2 currents, and a not near zero neutral current? Somehow try to repeat those conditions, and then remove all the cable connections. Does this change the neutral current to near zero?

.

Maybe he had an ‘aha’ moment and realized what he was doing.