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BANGKOK 20 July 2019 03:38
jd5

N-E high voltage

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Apologies in advance for the length…

BACKGROUND:

Small bottled water facility in Issan with 100 amp single phase service (at the time of construction, 3 phase was not offered in our area).

RCB 100amp breaker 50 meters from facility.

Had questionable electrician in the construction phase resulting in all underground wiring circuits had faults requiring replacement above ground last year. Also had one short in a 4mm wall conduit circuit requiring rerunning outside the wall.  Dodgy spark as later inspection showed many shortcuts taken in the conduits and general wiring although we did manage to ensure he used EU color codes for the main wiring runs BRN (L), Blue (N) and Green (E).  All sockets are wired the Thai standard way with N clockwise or Right (bottom, wide slot) of the Earth when looking at the socket.  

Although I purchased a 2.5 meter copper clad ground/earth spike I did not witness it physically being installed before it was covered in concrete so could not verify its connection as well as if it was actually used or if he may have stuck one of those 25cm long cheating rods in and sold the 1000 baht rod.  Unknown and I did have reason to doubt most all of his work. He never returned for the final panel install making for quite a job to identify the circuits in particular the Neutrals on a few which were determined to be shared between circuits in a few cases.  Disappointing.  

16 of the 27 circuit breakers in the main panel are RCBO.  In retrospect, I should have used RCBO on all circuits but I did try to cover anywhere there is or may be standing water. The shared neutrals were part of the problem for RCBO in a couple of cases.

We have been suffering with low voltage from PEA since 2016 prompting me to install a LiOA SH-20000 Automatic Voltage Stabilizer (AVS or AVR) before the Main box. I grounded this transformer with 20mm copper earthing cable back to the main box strip as well.  I also installed Volt and Amp meters on both sides of the AVS allowing me to see and time-lapse video the low power while trying to protect my pumps and motors around the little factory. Many complaints logged with the PEA including some down right scary 125 vac video evidence.  Finally, after two years of complaints, we are told within a month they will complete a budgeted/funded project to add 6 more transformers on the grid nearby so our low power issue will be resolved soon... I hope.

RECENT BACKGROUND:

Last week the PEA changed our meter (the old one slowed and then finally stopped turning for some reason). Tests around the premises generally show okay when using Schneider IMT23003 UK plug Socket Tester with Toshino Cord to reverse L and N.  Random testing after the meter change occasionally showed PE error.  This error comes and goes leaving me a little uncomfortable and prompting me to purchase a second Habotest HT106B Socket Tester with US plug last week.

The Habotest indicated “Live/Grd reverse, missing GRD” The Left and middle lights bright and the right light dimly glowing.  When measuring with a multimeter between N-E I was getting (what I thought to be) higher voltage numbers than should be present.

Reading Crossy’s comments on older posts I installed a new ¾” copper clad ground/earth rod and 30 meter 25mm back to the main box screwed down along with the existing ground cable to rule out a poor ground.  It made no difference apart from the piece of mind that now I can see it and do maintenance when necessary on the connection.

QUESTIONS:

  (1) Should I be concerned about the high N-E readings (see below attached table graphic)? 

- (2) Is this something I can do anything about? or is it a PEA issue?

-         (2.1) If it is a PEA issue, should add to the complaints to the PEA if the high N-E voltage persists once they put a transformer closer to my premises?

  (3) Are there more recommendations to keep our staff safe around the premises?

  Thanks to any and all that can lend some thoughts or guidance...

 

Meter readings with 4 load levels:

image.png.89c8a33ea998898fff0f30a5523ab39a.png

TV_Post_20190618_1229jpg.jpg

HABOTEST_20190618_1239.jpg

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Sorry for the typo in the subject line. Obviously should be:  "N-E high voltage"

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Do you have a local bond between neutral and earth at the main panel?  Do you have any in other panels?

 

Can you read the current on your earth cable to the ground rod?  Do you have any issues with your RCDOs?  Did you disconnect the original ground rod?

 

What you describe can be caused by circulating earth currents or a poor earth connection.  It is a sign of a minor problem that warrants investigation, but should not be a major safety issue. 

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1 hour ago, jd5 said:

Sorry for the typo in the subject line. Obviously should be:  "N-E high voltage"

 

Fixed for you 🙂

 

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As noted earlier, do you have a N-E bond? Where is it?

 

Assuming no N-E bond I suspect a high impedance joint in the neutral. How to locate it? 

 

I'm assuming you have a multimeter, if not go and buy one.

 

Measure before the AVS. L, N and E to a good earth (big screwdriver in the lawn) at your various loads.

Go to the meter and make the same tests (no E at the meter of course).

 

Come back with the results.

 

 

 

 

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Thanks for the comments and the subject line repair :-)

tjo otjim and Crossy, I'll try to answer in the order the comments/questions came in:

 

(1) Forgive me for possibly misunderstanding any Sparky lingo but is a local bond the steel box between N and E in my main breaker box?  Or is it a dedicated cable between the two?  Which begs the question should I tie the two together with a cable in my main panel? (see photo) 

When I look closely, I don't see that even the steel panel/box connects the N and E as the N is on nylon (or plastic) mounts whereas the E is fixed directly to the steel panel.  This is an area most certainly out of my wheelhouse but I reckon it could use a jumper cable between them (RE the Schneider document attached), right?  Don't worry, I will not put a jumper cable  (local bond?) in unless you guys agree it should be done.

 

(2) I have no sub-panels apart from one three breaker (3 x 2 pole WiFi breakers) panel downstream from three breakers (for remote control of some pumps after hours as my house is 55 km away) so its not a proper sub-panel (upstream of any service breakers) and its box is grounded with 4mm wire as well.

 

(3) New Earth cable to New Ground Rod = 0 volts, 0 amps.  The old Earth Cable and Ground rod are still intact (at least from what I can see and those meter values on the new one).  Perhaps next time I shut down the power (some Sunday typically) I will disconnect the old ground and take readings again to prove it is in fact working for my own piece of mind.

 

(4) I know of no issues on the Schneider RCBO breakers and as far as I know (which admittedly is not much) none of those Neutrals are shared with non-RCBO breakers... at least not that I remember when we (myself and a better qualified electrician) installed the main panel and were chasing/labeling each circuit.

 

(5) Original earth/ground is still intact

 

(6) For the measurements with a big screwdriver in the garden, I did so at the PEA meter (so 70 meters before the AVS) with medium load: 44 amps, L-E 202vac (this is my screwdriver earth), L-N 191.6vac, N-E 10.6vac (see photos). 

 

I may be able to get more measurements if needed but with our dynamic loads its a bit hard to run between the meter at the road and the facility 70 meters away while maintaining the same load during a work day.  Saying that, if necessary for the diagnostics I will take a Sunday and set the loads more precisely while making all necessary meter measurements.  Please advise and I will do whats needed for sure but I kind of feel like (1) has the answer at the moment. Please correct me if I assumed too much here.

 

Oh and that 100 amp main breaker in the photo has a jumper between the two outer conductors above it which cannot be seen in the picture to provide for two columns of breakers.

 

Thanks again for those comments and any further advise.  This forum is a great resource for those of us that want to do things properly but can't seem to find the right local professionals to do so.  I do hope what comes from this helps some others.

Reply_TV_20190619_0947.jpg

Reply_TV_20190619_0946.jpg

Connecting E&N Outside Main Panel.pdf

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2 hours ago, jd5 said:

2) I have no sub-panels apart from one three breaker (3 x 2 pole WiFi breakers) panel downstream from three breakers (for remote control of some pumps after hours as my house is 55 km away) so its not a proper sub-panel (upstream of any service breakers) and its box is grounded with 4mm wire as well.

I do hope you mean 55m not 55km

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Nope, little factory in Nongkhai, home in Udon Thani ~55km.  I monitor and manage the three WiFi breakers (pumps and an out building power) with an Android phone app.

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Assuming you have a nominal 220V off load.

 

Load 44A, your N climbs by 10V above true ground, L drops by 18V towards ground. Leaving you with about 192V L-N.

 

I would suggest that there's not a lot wrong with that supply apart from a supply impedance of about 0.6 ohms (ours on a 15/45 is about 0.5 ohms).

 

How far away from the meter is the transformer?

 

I would NOT add a N-E link at this time, it does seem that your neutral isn't well grounded locally which it would be for proper MEN. You could have a look at the poles to see if there are any neutral grounding rods (every 3rd pole).

 

It would be useful to take similar measurements at your incoming breaker (roughly the same load but not exact) just to confirm that there's nothing odd going on between the meter and the incoming breaker.

 

You seem to have a 3-phase panel wired for single-phase (that's the jumper between phases. Not a lot to worry about there.

 

EDIT I also seems you have a 3-phase meter but don't have a 3-phase supply. Any idea why? If there's 3-phase at the pole it may well be worth removing the single-phase kit from your board and running the installation off 3-phase.

 

 

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Thanks for the comments and suggestions Crossy!

 

RE Distance from Meter to Transformer: I happen to have the PEA map of the area so I stepped if off today its ~440 m currently with an oversubscribed transformer (see map)

 

I did see that my pole (see photo) seems to be grounded and roughly every third one has similar (some were covered in jungle so I could not see properly)

 

I took more measurements at the meter and at the panel however the panel measurements are after the AVS.  Again the load is pretty dynamic here so not measured at the same moment/load.

 

I also measured (as best as I could) between the pole ground and my big screwdriver ground which was about 230 ohms.  The  N-Epole and N-Escrewdriver  were only about 0.5 volts different which could have been caused by the load changing while testing.  I feel like the PEA pole earth is satisfactory after testing.

image.png.1ddeaf83dc76c9bd2d673dc1bbde44cd.png

RE the three phase equipment.  We had purchased three phase panel and main breaker in hopes of starting off with three phase originally.  The PEA informed us that it was not available at our location and that we would need to pay for bringing the 3 phase from across the street and purchase their transformer to do so which would take time and more money than I was prepared to invest in PEA equipment.  I would have preferred to use those funds to purchase full rooftop solar as we have a south facing sloped roof.  In any case, we “settled” for a 30/100 meter and service.

 

I don’t know why the PEA installed a three phase meter to replace our recently malfunctioning single phase meter but I’m glad they did so we have the option in future as we are close to the high limit of the 100 amp service now. Once the new transformers are in, I suspect they will offer 3-phase to us.  Here is a little cartoon of the general wiring picture: 

image.png.14774bbd4c343ae9883e4aee2f42cd80.png

 

I suppose my last questions would be:

(1)    If it is unnecessary to bind the Neutral at the main box, should I bind it anywhere else?

a.       At the first breaker 10 meters from the 30/100 meter before the cables go underground with another ground rod?

b.       At the AVS on the input (PEA) side Neutral to Earth in the main panel?

(2)    It sounds like I should not worry too much at least until the PEA install the new transformer with less subscribers. Should I be doing anything else in your opinion?

 

Once again, many thanks for all your help and the expertise you guys lend to the community. 

MapNewTransformer.jpg

Transformer2.jpg

OurPole_meter.jpg

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Can i ask what size cable your running from meter to shop?

25,35 or 50 aluminium

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It's worrying that you are getting significant neutral-climb with what appears to be a MEN system but 440m is a pretty long way meter to transformer.

 

You would normally have only one N-E link in an instalation and that MUST be before any RCD/RCBO or you'll never get the breaker to stay on.

 

Since a new transformer is going in soon I would do nothing for now, you don't have a hazardous situation and things are working "reasonably well".

 

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1 hour ago, farmerjo said:

Can i ask what size cable your running from meter to shop?

25,35 or 50 aluminium

Good question farmerjo.

I did some voltage drop calculations back when I was complaining to PEA about low voltage prior to purchasing the AVS and came up with ~3.5 vAC drop due to the ~70 meter length. I also recall my original electrician recommended 25 mm2   I went with 35 mmcopper on L and N instead. Original E is also 35 mm2 copper left over from one of the rolls.  The second E, installed a few days ago, is 25 mm2 aluminium (I know its not really the best secondary grounding, that's all I could find that afternoon without buying another 100 meter roll of 35 mm2 copper).

 

43 minutes ago, Crossy said:

It's worrying that you are getting significant neutral-climb with what appears to be a MEN system but 440m is a pretty long way meter to transformer.

 

You would normally have only one N-E link in an instalation and that MUST be before any RCD/RCBO or you'll never get the breaker to stay on.

 

Since a new transformer is going in soon I would do nothing for now, you don't have a hazardous situation and things are working "reasonably well".

 

Thanks for this, Crossy... makes me feel much better.  I'll call it good for now then do extensive testing after PEA installs the new transformers.

 

I will make one more comment regarding the PEA service in case others can benefit:  We got absolutely no help from the local PEA office in Nongkhai.  We made written, telephone and face-to-face complaints numbering at least 3 per year.  I did make some time-lapse videos of my voltage and amp readings to prove to them that they were not meeting the minimum levels since they always wanted to come check after working hours.  Some times of the day its is downright scary when loads are heavy (see example photo).

 

After being fed up with the local PEA I wrote a detailed email to the head office hotline: 1129@pea.co.th.  This had YouTube links to the same time-lapse videos, descriptions of our low voltage story and I CC'd the Deputy Governor Operations and Maintenance (who's name and mobile number Google kindly provided) with a guess at his email address.  This did get a response and within a month we had a visit by the manager and a lead engineer announcing a budget fulfillment and action plan to upgrade the area's transformers. 

 

Not sure if evoking the name of the Deputy Governor (albeit an incorrectly guessed email address) or just complaining to the head office made things start to happen but I suppose I can recommend the hotline route rather than the local office.  Be warned however the feedback survey email sent last month from the hotline service had ~250 email address of from what I assume are all of the recent complaint filers in the TO (instead of BCC section) section which I found a little insecure.  If one decided to go this route, you may want to use a disposable email address.

 

Any solar companies out there want a list of disenchanted PEA customers?  😏

 

Thanks again for the support, gentlemen.

image.png

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How far away is the nearest 4-conductor PEA pole?  Your issue might be caused by phase shift with a single overloaded phase. PEA might be able to re-balance the transformer loads and put you on a different phase of the existing transformer. 

 

But, a new, closer, 3-phase transformer and loads are a much better solution. 

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tjo o tjim, 

I think the nearest currently is ~440 meters away. 

 

NOTE: In early 2018 the local PEA did say they would check the load balancing and try different phases.  They also said they would inform me prior to doing so so I could turn on a camera for time-lapse recording of volts/amps to verify the results.  Alas they never called and we saw no evident change.  This was the trigger for me to send a message to the head office hotline.  I'm going to assume since the PEA budgeted installation for something like 6 transformers in the nearby area they are oversubscribed on all phases. 

 

Thanks for your comments/questions.  I think I shall do nothing until they install the new transformer which will still be ~375 m away from my meter.  If the situation with N-E voltage persists I may add another ground rod bound to the upstream N of the first RCD breaker and see if that helps at all.  If the low voltage persists after the new transformer installation, I may need to take on the task of swapping over to 3-phase and manage the load balancing within circuits of the main panel. I may need to do this in the future anyway if we add any more equipment once 3-phase is made available.

 

Many thanks for taking the time to help.

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