i used screwdriver to check neutral screw. 1-2 can be tightened 1/8th turn. rest are ok. neutral-earth voltage at this point 0.72v

 

you don't think problem could be the pump control circuit board.i remember all these problems began after the house was struck by lightning

To be honest all your voltages seem reasonable, 250V P-N is a little high but not dangerously so.

 

If you leave off the "badly insulated" circuit do the other problems go away permanently? (by "off" I'm assuming you are turning off its breaker)

 

Are you MEA or PEA?

Do you have an RCBO?

Please post an image of your board with the lid off so we can see what you actually have in there.

 

Ah, more information, lightning strike!

 

Pull the plug on the pump if you suspect the controller.

 

Was a lot of kit fried by your hit?

 

Ah, more information, lightning strike!
 
Pull the plug on the pump if you suspect the controller.
 
Was a lot of kit fried by your hit?
 

Yes, good to know about the lightning strike.

This also raises another thought to me, .....red ants. They cause all sorts of unexplainable symptoms.

Hopefully lightning strike investigation will find the prob.

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yes you are right crossy 250v is high but not dangerously so

 

with the bad switch off, flickering at night is mostly gone but fluctuating voltage still remains

 

is it possible to determine right now the problem is definitely in the house and not before the pea meter?

 

and if the problem is on the pump control or the pump, how is the faulty board or capacitor able to cause over/under volt between phase and the situation to be reversed in the next instance? seems to be oscillating....if there is such a thing in the pump circuit

 

 

It is highly doubtful that anything involved with the pump is causing your issues (that's not to discount it entirely of course), if you disconnect the pump do the problems go away? Does moving the pump onto a different phase make any difference?

 

As to the voltages. Where in the circuit are you checking the voltage? You need to be consistent. I suggest making all the measurements at the incoming side of the main breaker (should be an MCCB). Any fluctuations there are coming into your system from outside. It's still possible that there's a high-resistance joint between your board and the meter, but you wouldn't be fixing that yourself anyway.

 

A daft question, when you say "flickering" do you mean the lights are partially on when switched off?

 

i will move it to a different phase and try

 

you mentioned another member had problem about fast spinning fan caused by high resistance joint. was it an intermittent problem and only overvoltage problem?

 

i do not observe the problem when the pump is disconnected.

 

lights flickering problem at night when the lights are on. not when they are off. series of flashes due to LV fluctuation as you mentioned. mostly resolved

1 hour ago, namdocmaimun said:

you mentioned another member had problem about fast spinning fan caused by high resistance joint. was it an intermittent problem and only overvoltage problem?

It was intermittent due to the nature of the poor joint in the neutral and the fact that his load was actually pretty well balanced so there was little neutral current anyway. Things only went awry when there was a decent load on one phase.

 

You may wish to try measuring between your incoming neutral and a known ground (not your own earth rod), I use a big screwdriver in the lawn well away from the system rod. If you never get more than a few volts it's pretty certain your neutral is good. Turn on a big single-phase load (water heater) to try to pull the neutral away from zero. 

can i say the intermittent nature last 30 seconds to 1 minute?

 

did he experience overvolt on all phase? how about undervolt?

can i say the intermittent nature last 30 seconds to 1 minute?

 

did he experience overvolt on all phase? how about undervolt?

I'm not sure where you're going with this.

In a recent post you said the flickering had sort of resolved.

You ask about the problem maybe incoming, but it doesn't seem you've checked with your neibour's to see if they have the same problem.

You say you measured 230 v incoming but on the equipment side 250 v.

I think you said it really all started after a lightning strike, but no more detail of what the strike took out.

To me, I can't see that you're any closer to find the fault.

Sorry if I've missed something.

 

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9 hours ago, namdocmaimun said:

can i say the intermittent nature last 30 seconds to 1 minute?

did he experience overvolt on all phase? how about undervolt?

It varied with his load, but it didn't need much to pull things out of balance. The nature of an open or high resistance neutral is that one phase (the heavily loaded one) goes under-voltage and the other two go over (how much also depends upon load).

 

Like @carlyai I'm wondering if we are going in circles with this issue, which is, apart from a possible insulation problem on one light circuit, not really that major.

 

If you're really worried about that low resistance reading on the lights it's time to start taking off switches and fittings to isolate where the problem lies. You really should have a proper insulation tester.

the flickering lights had mostly resolved. what remains is maybe the occasional blip from HT voltage.

 

i moved the water pump to another phase and am observing. i also remembered the using the angle grinder when the voltage went soft.

 

the duration of the undervolt/overvolt varies from 30s to a few minutes each time it occurred.

 

also i rechecked again all possible neutral connections and remeasured N-E voltage at .19-.25v

3 hours ago, namdocmaimun said:

also i rechecked again all possible neutral connections and remeasured N-E voltage at .19-.25v

That's very low for a TT system which you say you have (we really do need some photos of the board).

 

Did you measure as recommended against an independent ground (big screwdriver in the lawn)?