intermittent flickering of lights

[namdocmaimun]

i experience flickering lights 2-3 nights a month. should i be concerned?

 

the voltage is always 228-229V

[carlyai]

i experience flickering lights 2-3 nights a month. should i be concerned?
 
the voltage is always 228-229V

Are they all flickering or just some?

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[namdocmaimun]

2 minutes ago, carlyai said:

Are they all flickering or just some?

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all, but some are flickering more than others. they are on different phase and different circuit

[carlyai]

all, but some are flickering more than others. they are on different phase and different circuit

Have you got voltage stabilizers or LED lights, and what happens to the neighbours lights or street lights when you have the problem?

I think you have to narrow the fault down as it's only intermittent, but on all phases. Sounds like it is incoming if on all phases.



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[carlyai]

Just a thought ...have you got industry near you, like 3 phase machinery or welders?

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[Crossy]

As others have noted, it's likely incoming supply dips. They are a fact of life here, annoying but unlikely to be damaging.

 

Since you have 230V I'll assume you are in Bangkok (MEA supply 230V).

 

Provided you don't have any "interesting" smells or fizzing noises I think you're fine, but it can't hurt to check all the terminals in your distribution board for tightness. Power off of course but remember those on the incoming side of your main breaker will still be live.

[namdocmaimun]

thanks. is it possible to have a brownout while still having normal voltage?

 

when the washer enters into spinning cycle, all the lights dip like power nearly cutoff. before that i am quite sure the voltage is normal, lights at normal intensity.

 

this also happens once in a while. no other device drawing big current. only fridge

[carlyai]

thanks. is it possible to have a brownout while still having normal voltage?
 
when the washer enters into spinning cycle, all the lights dip like power nearly cutoff. before that i am quite sure the voltage is normal, lights at normal intensity.
 
this also happens once in a while. no other device drawing big current. only fridge

Hi, but I thought before you said all the lights flicker (on/off, on/off rapidly)?

You also said you have 3 phase. Do you have all the lights on the same phase?

Do you have a 3 phase washer?

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[bankruatsteve]

2 hours ago, namdocmaimun said:

when the washer enters into spinning cycle, all the lights dip like power nearly cutoff. before that i am quite sure the voltage is normal, lights at normal intensity.

 

this also happens once in a while. no other device drawing big current. only fridge

A brown out happens when there is demand from the grid that it can't quite supply and voltage drops.  Your washer will drop the voltage initially but should then return to normal.  If you are the cause of the voltage drop, others on the same transformer will notice also.  The same vice versa.

[namdocmaimun]

the intermittent flicker of lights happen at night. this is the 1st situation

 

the washer situation is in the morning and happen once every few months. it is a 2 pole washer. this is the 2nd situation.

 

the 3rd situation is sometimes the light hum to the same frequency of the fridge. it is not flickering but still noticeable. and they are on different phase.

 

the 4th situation is sometimes the fan would spin faster than normal. maybe setting at speed 1 but spin at speed  3. and maybe somehow linked to a water pump running on a different phase.

 

the 3rd and 4th situation are more frequent.once every day or 2. but short time few seconds to 1 minute.

 

could all these be linked to wire running in same conduit and voltage or harmonic interaction between the phase?

[sometimewoodworker]

9 hours ago, namdocmaimun said:

is it possible to have a brownout while still having normal voltage?

No. A brownout means that the voltage drops drastically, probably under 180v though that isn't exact.  It sounds as if you really need some metering on your supply, so you can go to the PEA with facts.

 

my supply has under over protection so it will cut off instead of damaging any electric motors that may be running.

[Crossy]

OK.

 

Have you checked your distribution board connections for tightness? (Care!! Power Off!)

 

What kind of lights do you have? Tungsten, halogen, CFL, fluorescent, LED? Do some flicker more than others?

 

Is the flickering one flash, or a whole flash-flash-flash ... sequence (HV switching tends to be one flash).

 

What are you using the measure your supply voltage?

 

Your fan running fast is worrying, could be an indication of over-voltage or an iffy neutral on 3-phase, if it's associated with your water pump running I would definitely be looking at that neutral. Run the pump and measure each phase-neutral voltage.

 

[carlyai]

@Crossy a question please: why could an intermittant fast running fan, indicate a HR neutral connection? If the neutral connection is intermittent high resistance, wouldn't the fan be at normal speed then dip slower?

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[Crossy]

Just now, carlyai said:

@Crossy a question please: why could an intermittant fast running fan, indicate a HR neutral connection? If the neutral connection is intermittent high resistance, wouldn't the fan be at normal speed then dip slower?

2

It would on a single-phase supply. But, an open or high-resistance neutral on a 3-phase supply can be really (really, really) bad news.

 

With no neutral to keep it in place the star point will drift towards the most heavily loaded phase pulling the lightly loaded phases upwards. In the absolutely worst case situation, you can end up with 400V L-N, not something you want.

 

This is why 4-pole MCBs etc. have a way specifically marked as "Neutral", this way opens last and closes first ensuring that you never have a situation with energised phases and no neutral.

 

This is why our OP must check his board, particularly the incoming neutral for good connections.

 

[namdocmaimun]

the distribution board is clean with no burning

 

cfl installed indoor. mostly they flicker at same rate, but i have noticed one odd occasion different rate flicker for lights on different phase

 

flickering is series of flash. sometimes they last few minutes. but there are 1-2 times they last the whole night. most equipment off at night except fridge

 

i use digital multimeter to measure the voltage

 

do you mean overvoltage like sudden spike above normal overvoltage or consistently high voltage above the standard 380v?

 

the normal voltage each phase is 385-395v somedays 400v on 2 phases. 3rd phase is 5-7v lower. i show peaa these figures already. seems to be the normal situation here

 

 

[Crossy]

Your phase-phase voltages look ok.

 

Please measure each phase to neutral, off load.

 

Then run your water pump and fan and check again (does the fan run fast?).

 

EDIT A daft question, the lights are flickering off when turned on aren't they?

 

EDIT 2 A digital meter won't react fast enough to see the voltage dips, this is one of the times an analog meter scores.

 

[carlyai]

@Crossy sorry for the follow up question: so if it is a neutral problem ( seems to be the common denominator), it could be from the PEA poles in, or from his connecting box in. If his neutral is earthed at his box coming in, how does that effect the equation?

He could also look at the PEA poles, the top neutral wire, and see if the feed is common to his and his neibour's houses and if it is, see if they are also having trouble.

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[Crossy]

@carlyai yes, it could well be a problem with the supply neutral, which is why Phase-Neutral voltage checks are required.

 

We had a member a while back who was having similar issues, turned out to be a bad joint in the neutral between his meter and the PEA overhead (PEA fixed it once showed the happily fizzing joint).

 

EDIT With a neutral-earth link in the board (MEN connection) the local rod will help to keep a disconnected supply neutral nearer to ground than it would be if allowed to float. A negative effect would be that all "earthed" appliances would become live and potentially lethal (just how live would depend upon the connected load and resistance of the ground rod).

 

[namdocmaimun]

the lights are ok when turned on initially.

 

p1-n,p2-n,p3-n:

 

with pump off, 229.5v,229.1v,224v

pump on and running,

225v,229v,224.6v

pump on and not running,

228.5v,228v,224.3v

 

so i turned off the pump and noticed the fan spinning slower and measure again:

 

250v,215v,224v

 

at this point only fan and fridge running. i then switched off main mcb and measure incoming:

 

230v,230v,220v

 

after that i turn on main mcb and want to isolate fridge and fan for testing. but the problem cannot be replicated. fan is spinning at normal speed

[namdocmaimun]

pump on p1, fan and fridge on p2 and same line,mcb

[carlyai]

'250v,215v,224v' are you sure that first 250v reading is correct?

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[namdocmaimun]

yes correct i measured twice. the second time after turning off some equipment

 

the fan on p2 spins faster than normal sometimes so the situation could be reversed p1-n,p2-n 215v,250v. p3 unaffected

[namdocmaimun]

water pump fault? water pump controller fault? neutral line to water pump fault?

 

fridge fault? neutral line to fridge fault?

[carlyai]

yes correct i measured twice. the second time after turning off some equipment
 
the fan on p2 spins faster than normal sometimes so the situation could be reversed p1-n,p2-n 215v,250v. p3 unaffected

Oh well, I've run out of suggestions on what to check to isolate it further.

You have 230v incoming, but you measure 250 v towards the equipment.

One thing I noticed with my set up a while ago was that it's very difficult to check for lose connections under the alan key type screws. Mine were all lose and I bought another consumer unit, but it was difficult to see any burn marks under the screws. This probably doesn't make sense, I'll try to find some pics.
Be careful.


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[Crossy]

That neutral moving around is a bit worrying, how many HP is the pump?

 

Do you have MEN link in your board (N and E connected)? If not sure please post a photo of the board with the lid off.

 

[namdocmaimun]

there is no men link. pump is about 1hp.

 

so p1 i measure at 250v. and p2 i noticed it moved very fast down to 140-160v before coming to 215v.

 

could all these be caused by the badly insulated light circuit at 2kohm which is on p1 and shares part of the conduit with the other wires?

[carlyai]

there is no men link. pump is about 1hp.
 
so p1 i measure at 250v. and p2 i noticed it moved very fast down to 140-160v before coming to 215v.
 
could all these be caused by the badly insulated light circuit at 2kohm which is on p1 and shares part of the conduit with the other wires?

I think you need the link and I think at the moment we are chasing a neutral to see if it is properly connected and all connections are good.

When you took the cover off the Consumer Unit did you take any pictures, if so post them.

Could you also take a pic of how your earth rod is connected.

Did you check that all the connections were tight and secure?





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[Crossy]

7 hours ago, namdocmaimun said:

could all these be caused by the badly insulated light circuit at 2kohm which is on p1 and shares part of the conduit with the other wires?

Pretty certain not, even if your 2k measurement is accurate it's only 0.1A or so. Do you have an RCD/RCBO/Safe-T-cut?

 

Please post some photos of the board with the lid off, it could be something easily spotted.

 

I know you said everything was tight, but did you actually check with a screwdriver?

 

Since you have no MEN link can you check the voltage between your earth and the neutral?

 

Roughly how far are you from the local transformer?

 

[namdocmaimun]

switching off the badly insulated light circuit seem to stop the flickering lights.

 

but this is separate problem from fluctuating voltage.

 

with the pump running p1 is lower and p2,p3 higher at 218,236,236v. just as pump is about to stop, 210,250,230v. this is first situation.

 

the second situation described earlier normal voltage when pump running but after pump stop immediately voltage fluctuate 250v,215v,220v

 

the situation is sporadic and i take out the meter to measure when i notice the fan spinning faster or slower. p3 is also affected but the overvolt situation is reversed between p1 and p2

[namdocmaimun]

0.7v between neutral and earth under normal situation. will measure again when the fault occurs again.

 

about 100m from the local transformer