3 Phase Power Problems

[carlyai]

I have a 3 phase supply. They come from the PEA meter to an outside CU where 3 phases go to the house change-over switch, then to 3 single phase stabalizers. I am using the 3 phases as 3 separate phases with a common neutral. From the stabalizers the phases go to another inside CU to feed the house.

 

From the outside CU one phase goes to the shed, including pool pump and chlorinator and bore pump and irrigation pump.

 

For a week or more now strange things have been happening on all phases. 

 

If I look at the pool pump voltmeter, it reads sometimes at 185v and other times at 250v. Recently my 2 hp pool pump tries to start and makes a grinding noise, then the phase protector operates on Under Voltage. If I adjust the phase protector to 0 on time, and the pool pump voltmeter reads 250v. The pump will start and then if I stop the pump the voltmeter will read 220v. So just starting the pump can change the volts reading 30v. I have watched the pool pump voltmeter and with no load it can jump from 220v to 250 v and back to 220v. At the moment the pool pump won't start unless I fiddle with the phase protector.

 

So now if we go to the house, all 3 stabalizers are tripping at different times. 

I have the 2nd bore pump, near the house, not on stabalizer fed straight to a contactor, and phase protector. This pump fills the tank for our house water. The house water pump is on a stabalizer phase. Today I noticed that when the bore pump and house water pumps were on, all of a sudden the pumps started 'growling' and 2 stabalizers threw their circuit breakers, but only one pump is on stabalizer.

I've also noticed that when I turn on the kitchen tap and the house pump on the stabaliser kicks in, the kitchen LED goes very bright for an instant.

 

Now before I was thinking that it was a PEA problem as we had a big storm and things seemed to happen around then. But now I'm not so sure, as today seeing 2 pumps on and on different phases, one on stabalizer and one not on stabalizer, tripping the 50 A cct breakers on 2 of the phase stabalizers. The only thing that should be common is the neutral.

 

So now I'm thinking that it's my problem and thinking the only common thing is the PEA meter or a nuetral  problem. The meter is very old and was used on the 3 phase rice mill years ago. Probably over 20 years old as we've had it for 6 years.  The meter door has been missing for years.

 

Could it be the meter or meter wiring?

 

At no times have the main incoming breakers tripped only the stabalizer breakers.

 

 

[bankruatsteve]

By stabilizer, are you talking voltage regulator, or something else? Check for loose connections? 

[Metropolitian]

41 minutes ago, carlyai said:

...3 separate phases with a common neutral. ...

 

For a week or more now strange things have been happening on all phases. 

 

Sounds like something with the common neutral from the meter to the CU.

[Metropolitian]

Do check if the neutral from the meter all the way to the stabilizers are ok.

If they are loose currents from two/three phases will mix and give imbalance.

[carlyai]

31 minutes ago, Metropolitian said:

Do check if the neutral from the meter all the way to the stabilizers are ok.

If they are loose currents from two/three phases will mix and give imbalance.

Even the pool pump on no stabalizers has the problem, so I was trying to take the stabalizers out if the equation, that's why I was thinking of the meter or it's wiring. I don't know how meters are wired and if it's possible to lose the neutral there.

 

I'll have a look tomorrow at the neutral connections.

I can fairly easily strap out the stabaluzers (voltage regulators). Take them out altogether.

[Crossy]

What are your actual incoming L-N voltages? (check at the house and the meter if you can)

 

Are the AVRs trying to regulate (variacs moving)?

 

[carlyai]

36 minutes ago, Crossy said:

What are your actual incoming L-N voltages? (check at the house and the meter if you can)

 

Are the AVRs trying to regulate (variacs moving)?

 

I have to buy a new meter this week. 

I can here the variacs rotating but I looked at one of the variac meters and it was at about 250 v nothing was rotting, so I turned it off and on and it was back at 220v.

 

I'll chase out the wiring from the pole tomorrow and try and buy a new meter.

[RichCor]

I have the same suggestion as Crossy. Before you go any further, see what voltages PEA is providing you on each Phase. And as already mentioned, safely check all your connection points, that everything is tight and not fizzing away.

 

 

[carlyai]

10 hours ago, RichCor said:

I have the same suggestion as Crossy. Before you go any further, see what voltages PEA is providing you on each Phase. And as already mentioned, safely check all your connection points, that everything is tight and not fizzing away.

 

 

Yes I'll do that today. My really old analogue meter is broke so will buy a new one today.

[bankruatsteve]

I like to put one of these on the incoming main and both of my CU (which are after the AVRs).

 

https://www.lazada.co.th/products/newest-6in1-220v-100a-single-phase-digital-panel-ampermeter-volt-watt-kwh-power-factor-meter-with-split-ct-i552582257-s1007740222.html?spm=a2o4m.searchlist.list.5.4d1e4693cxH29P&search=1

[carlyai]

I checked the voltages at the first CU about 50 m from the soi and meter.

L1 = 195v

L2 =200v

L3 =205v

 

I can't easily get to the meter box.

 

I did see a small amount of red ants in the CU so blew them out.

 

I traced the neutral wire along the soi to the main village road (about 100m). All the PEA wires along the soi from the main road go thru various trees. One mango tree could be a problem as one phase wire and the neutral wire are rubbing together on a big branch. I think if this was the problem and they were shorting then we would have known about it.

At the moment "All Quiet on the Isaan Front". 

If no further suggestions, I'll wait to see if there are any problems when a house load switches on and have a look in the mango tree for any excitement.

Spose I can rule out the meter box as the neutral doesn't enter it.

Thanks for the help.

[carlyai]

14 hours ago, bankruatsteve said:

By stabilizer, are you talking voltage regulator, or something else? Check for loose connections? 

Yes I was talking about voltage regulators :).

[carlyai]

13 minutes ago, bankruatsteve said:

I like to put one of these on the incoming main and both of my CU (which are after the AVRs).

 

https://www.lazada.co.th/products/newest-6in1-220v-100a-single-phase-digital-panel-ampermeter-volt-watt-kwh-power-factor-meter-with-split-ct-i552582257-s1007740222.html?spm=a2o4m.searchlist.list.5.4d1e4693cxH29P&search=1

Yes a great idea and one I have on my list of things to do. I was going to get those old fashioned anologue voltage and current meters and build them in but probably never get around to it.

[Crossy]

9 minutes ago, carlyai said:

I checked the voltages at the first CU about 50 m from the soi and meter.

L1 = 195v

L2 =200v

L3 =205v

 

Those are a bit low for early in the morning.

 

I assume your AVRs are all putting out a nice 220V per phase?

 

[bankruatsteve]

14 minutes ago, carlyai said:

All the PEA wires along the soi from the main road go thru various trees.

You really don't want the trees enveloping the cables like that.  A big wind and you have big problems.  They really need to be trimmed back or cut down. 

[carlyai]

21 minutes ago, Crossy said:

 

Those are a bit low for early in the morning.

 

I assume your AVRs are all putting out a nice 220V per phase?

 

Good question. Answer is no. 

214v, 200v, 208v read with my meter.

Going by the AVR meters 2 should be at 220v and the third meter has read off the scale for ages but reads 214v at the AVR output terminals. (others seem to have metering probs with these AVR's and contacting the manufactures was useless so I put the meter problem in the 'in-hand' tray).

I can adjust the voltages with a small potentiometer adjustment screw.

There was another strange thing I noticed with one of the AVRs yesterday, that the voltage read very high (think greater than 250v )and it hadn't adjusted. Turned it off/on and it's meter read back at 220v.

[Crossy]

Hmmm, our AVR stopped regulating a little while back with a stuck variac. Thread here 

 

Can you move the variacs by hand with the power off (be careful, the moving arm on ours is live!!) ?

[carlyai]

14 minutes ago, Crossy said:

Hmmm, our AVR stopped regulating a little while back with a stuck variac. Thread here 

 

Can you move the variacs by hand with the power off (be careful, the moving arm on ours it live!!) 

I can hear them or an individual one hunting when an outside load changes. I'll have a look. 

Still doesn't explain the probs. with the other pumps that aren't in AVR's.

[Crossy]

Just now, carlyai said:

... with the other pumps that aren't in AVR's.

 

If the supply is going really low when the pumps try to start that may explain the issues.

 

[carlyai]

48 minutes ago, Crossy said:

 

If the supply is going really low when the pumps try to start that may explain the issues.

 

Yes I think that's the problem as when I try to manually start the pool pump, it tries to start, then grinds and the phase protector UV LED comes on. 

I've adjusted the AVR's as best I can to around 220v and they are all hunting, but it will be a good idea to have a look and see as they work very hard (up and down like a whore's draws) as my daddy used to day.

Someone's contacting the OPT and going to get some tree limb clearing done.

Maybe after some wild weather, PEA had a transformer problem and put in a temp. fix until a new order arrives?

[Crossy]

Can you put the pump on an AVR (at least temporarily) and see if the problem is solved?

 

We have everything except the water heaters on our AVR.

 

[carlyai]

6 minutes ago, Crossy said:

Can you put the pump on an AVR (at least temporarily) and see if the problem is solved?

 

We have everything except the water heaters on our AVR.

 

Not without physically shifting an AVR.

I think low supply voltage makes sense as the supply goes lower, the AVR's draw more current to compensate until they finally drop the AVR 50 A breakers.

A star/delta problem with PEA?

[Crossy]

17 minutes ago, carlyai said:

Not without physically shifting an AVR.

 

Even with a long extension lead a regulated supply ought to help your pump.

 

It's certainly a PEA problem but you'll need to go to them with some figures. Time to get out your notebook and log the supply voltages at 2 or 3 times a day, anything under 200V (-10%) should be regarded as an issue.

 

Enjoy!!

 

Edit If you log the voltages you may be able to find a time of day when the supply is "high" and adjust the pump timing to do it's job then.

 

[carlyai]

3 hours ago, Crossy said:

 

Even with a long extension lead a regulated supply ought to help your pump.

 

It's certainly a PEA problem but you'll need to go to them with some figures. Time to get out your notebook and log the supply voltages at 2 or 3 times a day, anything under 200V (-10%) should be regarded as an issue.

 

Enjoy!!

 

Edit If you log the voltages you may be able to find a time of day when the supply is "high" and adjust the pump timing to do it's job then.

 

Thanks. I can keep the pump running as it tries to start and then stops due to UV I adjusted the phase protector to 0 time on, so the pump initially gets a bit of momentum, cuts out then after a few hickups is running at speed. 

Will start monitoring and see how things go. Probably will need a few more start capacitors as well.

[carlyai]

0500 this morning started to log phase voltages: L1 =220v, L2 =220v, L3 =230v.

Thought I'd try the 2hp pool pump but when I switched it on there's a huge voltage drop and the pump just won'r start.

Family member live in house with a feed from the main road, not my soi. Got them to turn on the aircon and no problems with their house.

So still all the same problems under load, but static incoming voltage at around 220v. 

So might point back to the meter.

We're off to PEA this morning with ... not sure what story. 'Your voltage is OK but no current'. ???

Wifey will ask PEA to come and check the meter I think.

OPT inspected the trees yesterday and filling in the required paperwork for tree lopping.

I will move one of the AVR's if nothing happens today.

 

[Crossy]

You/PEA really need to check the voltage drop at the meter when you turn on big loads. That should enable you to determine where the problem lies, PEA or your installation and take appropriate action.

 

How big is this pool pump?

 

[carlyai]

7 minutes ago, Crossy said:

You/PEA really need to check the voltage drop at the meter when you turn on big loads. That should enable you to determine where the problem lies, PEA or your installation and take appropriate action.

 

How big is this pool pump?

 

Pool pump is 2 HP about 1500w.

[Crossy]

1 minute ago, carlyai said:

Pool pump is 2 HP about 1500w.

 

About 7A run current, say 20A surge on start. I can see that causing a dip (would be about 10V on our supply) but shouldn't be that bad.

 

Definitely something awry somewhere.

[carlyai]

16 minutes ago, Crossy said:

 

About 7A run current, say 20A surge on start. I can see that causing a dip (would be about 10V on our supply) but shouldn't be that bad.

 

Definitely something awry somewhere.

Yes thanks. I measured at the pool pump as can't really get to the meter box at the moment.

No load pool pump (2 HP) 230v.

Start load voltage drops to about 90v. About 40v drop. So this excessive voltage drop seems to be the characteristic on all phases.

Will see what PEA say this morning.

Thanks again for your help.

[Crossy]

4 minutes ago, carlyai said:

About 40v drop.

 

Ouch!