floating voltage

[FrazeeDK]

PEA did an upgrade to the neighborhood power yesterday installed what I guess is either a transformer or load balancer of some type. It was in response to folks in one part of the village having low current/voltage. They completed the job about 5PM whereupon when the power was turned back on ours was fluctuating where we'd never had issues before. I had to run down the street to catch them before they decamped. They found the voltage at 170 at my meter and went off to "fix it".. Our lights got all bright and when they came back to check it, the voltage was 270. Oops. back off again.. Finally around 9PM after cutting the power again, they restored it and all appeared OK and they left. It was this morning that we noted a "floating voltage" of 25Volts on our metal stove top and on the shower fixtures.. Enough to shock us. Any ideas how to neutralize this without going through the agony of trying to get PEA back out here? I imagine we've got a trickle of voltage down the return...

Power is solid 230 volts when measuring at outlet hot to return on a 3 prong outlet.

Power trickle (?) is 21 volts when measuring hot to ground on a 3 prong outlet (house is properly grounded.

[Bandung_Dero]

Firstly it is disturbing that your getting a "boot" of your HWS fittings, even the Thais know they should be earthed correctly.

Without looking at it myself I would guess the PEA have a ground fault at the star point (neutral) on their step-down transformer, measure the voltage between the Earth and Neural bars in your consumer box, should be close to zero. Unfortunately, in general, the Thais do not use the MEN system (Multiple Earth Neutral) where all consumer boxes have the neutral tied to earth thus stopping the neutral from floating over a wider area. Check your RCD as well, if the zap is enough to feel that should have tripped.

[sometimewoodworker]

Without looking at it myself I would guess the PEA have a ground fault at the star point (neutral) on their step-down transformer, measure the voltage between the Earth and Neural bars in your consumer box, should be close to zero. Unfortunately, in general, the Thais do not use the MEN system (Multiple Earth Neutral) where all consumer boxes have the neutral tied to earth thus stopping the neutral from floating over a wider area. Check your RCD as well, if the zap is enough to feel that should have tripped.

Sorry that’s not true, the Thai power system is mostly transitioned to TN-C-S with MEN, ours certainly is TN-C-S with a MEN link.

There are certainly areas that are pure TT. It’s not too difficult to check which you have as roughly every 3 power pole will have an earth to it. The other ways are to check if you have an earth neutral link in your consumer unit or ask the PEA.

[sometimewoodworker]

It was this morning that we noted a "floating voltage" of 25Volts on our metal stove top and on the shower fixtures.. Enough to shock us. Any ideas how to neutralize this without going through the agony of trying to get PEA back out here? I imagine we've got a trickle of voltage down the return...

Power is solid 230 volts when measuring at outlet hot to return on a 3 prong outlet.

Power trickle (?) is 21 volts when measuring hot to ground on a 3 prong outlet (house is properly grounded.

It is a little difficult to know exactly what the problem is without knowing quite a bit more. The line to earth voltage should be close to 230V the same, or close to, the line to neutral.

If you have a TT supply the PEA could have swapped the line and neutral connectors.

If you don’t have a RCCD or RCBO you would be doing yourself a favour by installing one, though the house wiring may not allow that. If you can’t install a whole house RCBO (required by current regulations) then installing a series of them on individual circuits may be OK

[andymu]

Earth leakage voltage. Earth is interconnected with a neutral conductor. Is it inside your installation or not. Does the consumer unit (fuse board) have an interconnection between neutral to earth ? What you can do is turn off every circuit (fuse) and do the same test that you saw 25v on your cooker. If its not there then one by one switch each circuit back on and test. This can isolate a fault to a circuit. Earth and Neutral are at the same potential, the difference being under normal conditions no voltage is on the earth conductor while the neutral will have voltage when in use. Another test that a qualified electrian would do is temporary disconnect your earth electrode and test again at the cooker for earth leakage voltage, reconnect the earth after testing. Having said that sounds like the fault is their end, new transformer and earthed it incorrectly.

[Bandung_Dero]

Sorry that’s not true, the Thai power system is mostly transitioned to TN-C-S with MEN, ours certainly is TN-C-S with a MEN link.

There are certainly areas that are pure TT. It’s not too difficult to check which you have as roughly every 3 power pole will have an earth to it. The other ways are to check if you have an earth neutral link in your consumer unit or ask the PEA.

I'm not going through another heavy duty "power" debate again other than to say:-
There are a lot of us who live in "olde 3rd world Thailand". Obviously the OP's electrician did not install the link.

You may remember why I installed dual pole isolation?

Let me tell you now there is NO WAY I will be installing a MEN link to have the only one in town. A fire waiting to happen!

[sometimewoodworker]

Sorry that’s not true, the Thai power system is mostly transitioned to TN-C-S with MEN, ours certainly is TN-C-S with a MEN link.

There are certainly areas that are pure TT. It’s not too difficult to check which you have as roughly every 3 power pole will have an earth to it. The other ways are to check if you have an earth neutral link in your consumer unit or ask the PEA.

I'm not going through another heavy duty "power" debate again other to say:-
There are a lot of us who live in "olde 3rd world Thailand"

You may remember why I installed dual pole isolation?

Let me tell you now there is NO WAY I will be installing a MEN link to have the only one in town. A fire waiting to happen!

Of course if you have a TT system you won’t be installing a MEN link.

I have never suggested that anyone whose supply is TT does that, as you say it a very bad idea, very probably dangerous as well.

But you said that MEN is unknown in Thailand. It absolutely is not, my area are all on MEN (TN-C-S)

The current Standard for new installs, it’s dated from 2016, is the TN-C-S

What you do in the privacy of your own property is up to you.

[FrazeeDK]

here's what they installed down the street. As you can see they've jumpered the three hots A, B, and C.. Is that a transformer or some type of line load balancer??

[FrazeeDK]

I've got a decent electrician coming tomorrow to check this issue as well as fix a number of small things..

[Bandung_Dero]

That's your step down transformer. The 3 phase HV is connected to the primary which has "Delta" windings (imagine a triangle with each wire attached to an apex) the secondary (220 VAC phase to neutral) is wired in a star configuration the star point being the neutral (the 4th connection, imagine a "Y" with 3 cables attached to the apexes and the star point being where they join). It should be Earthed securely in the transformer. OK simplistic!

[FrazeeDK]

PEA increased the size of the concrete pole footing by about 40cm's all around. They put in a ground rod at the next pole down with a cable secured to the side of that pole and going up. Where it goes I couldn't see but certainly it had to do with the installation of the step down transformer. Thanks for the explanation of what they installed.

[FrazeeDK]

BTW Bandung do you still think my floating voltage problem and some shocks off appliances and off the water fixtures in the shower are from PEA not properly installing or grounding the new setup?? Is there any remedy I can take at the house. The PEA team that did the installation was from out of town, a special job evidently.. Given the obvious improper initial installation that gave me 170 volts, then 270 volts then 190 and finally after them futzing around a solid 230 I don't know that the local PEA lads would do much more than try to blame the problem on something on my end. I subscribe to the adage, "who did what last" and if I didn't have this problem before the upgrade, it must have been the upgrade that caused my curren tissue.

[pal52]

Floating voltage can also be caused of a badly imbalanced transformer.

[bluejets]

BTW Bandung do you still think my floating voltage problem and some shocks off appliances and off the water fixtures in the shower are from PEA not properly installing or grounding the new setup?? Is there any remedy I can take at the house. The PEA team that did the installation was from out of town, a special job evidently.. Given the obvious improper initial installation that gave me 170 volts, then 270 volts then 190 and finally after them futzing around a solid 230 I don't know that the local PEA lads would do much more than try to blame the problem on something on my end. I subscribe to the adage, "who did what last" and if I didn't have this problem before the upgrade, it must have been the upgrade that caused my curren tissue.

It'll be your installation and lack of properly installed main earth electrode, MEN and/or inadequet earthing at your equipment.

Follow through the circuit that sometimewoodworker provided and you will see why.
If unable to follow the circuit, best to leave it to someone qualified.

BTW...after 50 years in the trade,I've yet to see load imbalance create a floating neutral.

[sometimewoodworker]

Here is the PEA document for you to print out for the person who comes to check your grounding and wiring.

PEA electrical info GroundwireMk2book-Manual.pdf

Thai language file

(803.56 KiB) Downloaded 143 times

Note that it includes the correct minimum ground wire sizes up to 2,500mm circuits and MCB sizes for copper conductors up to 35mm

[BillaRickaDickay]

If the problem is down to the Transformer upgrade, neighbours (if you have any) will be experiencing similar problems, unless they too have earthing issues.

[Bandung_Dero]

BTW Bandung do you still think my floating voltage problem and some shocks off appliances and off the water fixtures in the shower are from PEA not properly installing or grounding the new setup?? Is there any remedy I can take at the house. The PEA team that did the installation was from out of town, a special job evidently.. Given the obvious improper initial installation that gave me 170 volts, then 270 volts then 190 and finally after them futzing around a solid 230 I don't know that the local PEA lads would do much more than try to blame the problem on something on my end. I subscribe to the adage, "who did what last" and if I didn't have this problem before the upgrade, it must have been the upgrade that caused my curren tissue.

It'll be your installation and lack of properly installed main earth electrode, MEN and/or inadequet earthing at your equipment.

Follow through the circuit that sometimewoodworker provided and you will see why.
If unable to follow the circuit, best to leave it to someone qualified.

BTW...after 50 years in the trade,I've yet to see load imbalance create a floating neutral.

Congratulations on your 50 years of experience. Your ignorance astounds me!
All grids have phase imbalance, NO Consumer grids are balanced perfectly, without MEN we rely on the star point integrety, and apart from that the further from the transformer one is located the higher the floating neutral.

Without very good consumer installation this floating neutral will create problems

You need to consult your manuals and do the maths. Should be simple for one of your experience!