What causes Voltages to sometimes cycle many times a minute?

[gdhm]

Hi ,

 

History

Back in 2008/2009 our power supply for everybody in our soi was appalling for the first year after our house was built in Khon Kaen City (Naimuang -so not a village or rural area) at its worst ranging between 217 Max during week early in day to min of 167V early to late evening ( Cool season Nov). After being palmed off by one or two Departments and their staff for nearly a year, someone at the PEA office kindly suggested to my wife we bypass those we were always directed to, and ask to see a Senior Official.  Great advice as the person we saw was not only sympathetic but agreed my recorded (proved Voltages) were not acceptable and that the PEA would fix the issue (free of charge).  Within 6 weeks our soi had 2 new lines (or so the installing engineer told us verbally) and all houses had decent power voltages. Our home's supply for the next 2-3 years was nearly always around 225V -235V most of the daylight hours during the week and never under 214-216V at night even during hot season when Air Cons were used.

 

Recent History

During the last couple of years I have noticed a general decline in average voltages. I know some largish houses have been built in our soi so I assume they were added to our line thus increasing the load/demand . I also suspect maybe at times house have been moved to different power lines in the soi maybe to balance voltage in the lines.  A few years ago in a major storm all our Soi lines were completely cut when a large tree uprooted and (just out luck toppled across over the power lines (I have no idea if houses in our soi wer ere connected to the same line they were on previously.

 

In recent months 2 of the few power cuts we have had, have been blamed on Transformers. On one occasion, a storm had just started so that was probably due to a lightning strike close to a Transformer. I think our nearest transformer is about ½km from our house.

 

Currently

During the last 6 months in particular I have noticed our Air fans SOMETIMES cycle many time a minute fast then slow then fast etc. I am sure the voltage is cycling but its nothing to do with our house.

 

During this last week I decided to check voltages as I did back in 2008/09 but this time via my APC UPS PowerChute software which I feel is slightly more accurate than the Multimeter I used before (and still have). I did check them out with each other and they agree with each other usually within plus/minus 1V.

 

This afternoon (26 June 2016) I noticed my fan cycling again, so I took readings over a 5 minute period. Below shows the changes and as you can see the variations and range are not consistent. No Air Cons were on in our house during these readings BUT had ONE 18000 BTU been on ,all these Voltages would have been 6V lower or 10-12V lower with 2 Air Cons running. It therefore suggests (to my amateur mind) that  the transformer supplying our Soi (and no doubt other sois)has Zero spare capacity (or the PEA struggling to cope with demand and is significantly cutting back on Voltages supplied at times) as the transformer seems unable (after the expected initial "switch on" surge) maintain voltages when Air Cons, Shower or Water heaters or other demanding appliances are switched on (not only in our house but others along same the power line we are on.

 

3:37pm to 3:38pm      208V, 220V, 212V, 220V, 210V, 216V, 220V, 218V

 

3:38pm to 3:39pm      220V, 208V, 220V,222V

 

3:39pm to 3:40pm      220V, 218V, 220V, 214V, 220V

 

3:40pm to 3:41pm      220V, 204V, 220V, 218V, 220V, 214V, 220V

 

3:41pm to 3:42pm      220V, 208V, 220V, 212V, 220V, 208V, 210V, 220V, 208V, 220V, 210V,  220V,  216V

 

Can anybody who has understanding of such matters advise me of what is the most reason  for such cycling (sometimes a 10V difference) AND what the inability to maintain stable DECENT voltages mean (I have searched the Web but cannot find an answer (maybe using wrong search terms) ?  Are the two connected to the same issue?. 

What seems crazy to me is if 2 Air Cons go on in our house at night we get a maintained full 10-12V drop (one Air Con is lower BTU) so you can tell that the voltages at night are down to 180V or below (just for my Air Cons alone) (Have not yet tested Volts after having one to eb when most peoples (and our 2 Air Cons will be on) .

 

I hasten to stress the cycling I have observed is periodic and is seemingly randomly . I have not yet found a pattern for day or time of day (if there is ANY pattern at all, I would say I have noticed more cycling between 7:00am and 11am (BUT that may be because I am close to a fan at this time of day). The periods of cycling usually only last for 5 - 15 minute periods (I know it is not a Microwave in our house being used at the time which I have noticed in the past can cause Voltage cycling.) .

 

I believe Thailand has 220V as norm and I recall Crossey saying on the Forum an acceptable swing should be no more than 10% either side of that (forgive me Crossey if my memory is inaccurate).

My current thought is that maybe I will soon need to visit the PEA Office office again with my observations and readings. 

 

I have noticed that my APC UPS is kicking in more and more recently to deal with momentarily "under voltages" set to trigger below 180V.  My APC UPS is only on LOW sensitivity (not advisable for a PC but its kicks in much too often if on Medium or High sensitivity. Luckily I have a decent PC PSU which copes very well with voltage swings, so the low sensitivity setting does not seem a serious issue yet, BUT it is far from ideal and I should NOT need to be on the low sensitivity setting if our soi's power supply was anything like stable (I have never had a power spike. APC UPS is set to its lowest max of 256V). 

 

I suppose after we had our new line back in Dec 2009 we had surplus capacity and were spoilt for a few years  with daytime Volts often 230V-235V and never worse that 225V

Now 222V is the highest I have seen ONCE at any time during the last 10 days.  My increasing concern is that I do not expect to see 9:30am weekday readings often being around 206V and then increasing on average between 212V to 218V during the period 12:30pm and 7:00pm (before tailing off significantly). This is very different from back in 2008/2009 where the highest Volts were between 9am to 3pm weekdays and decreased steadily thereafter (which I expected, as people were not at home during the day, but of course demand increased as they returned home from work. 

 

NOW, expected Lowest demand periods seem to have lower Voltages than period where I would expect a decline rather than an increase PRIOR to evening peak usage periods).

Does anybody have any ideas what on Earth is going on?   I believe I need to have a reasonable idea in order to avoid being palmed off if I visit PEA Office with my findings (that's assuming those more knowledgable than me agree Volts and consistency are not currently as they should be) 

 

Kind Regards and many thanks to those still reading to this point

 

[Crossy]

220V +- 10% is 198V to 242V. All your readings are within this range by a margin, but evidently there are short term blips to much lower levels which your UPS is managing for you.

 

Are the variations causing you issues other than hearing the fan slow down, seeing the lights flicker or triggering the UPS? If not, worry not, there are far greater issues in this world.

 

If so, then it may be worth hiring a proper supply monitoring device (sorry can't help there) and going to PEA with some real, irrefutable data.

 

[impulse]

I don't know if I'm reading the OP correctly, but if turning on one or two A/C's caused my voltage to sag by 10-12V,  I'd spring the $200-300 for a FLIR attachment for my smartphone, and have a gander at the temperature of my wiring.

 

We use 30 volts per 1000' as a maximum voltage drop, because any drop higher than that can cause the insulation to melt.  I recall that came from the NEC, published by the NFPA in the USA.

 

I'm a mechanical engineer (not an E-), and don't hold myself out as a household power guy, but dropping 10-12V steady state in a short run in a typical suburban setting would raise my alarm bells.  With starting amperage running 5-7 times running amperage, you could drop 50-80V on startup so your surges may be motors trying to start and not getting the voltage they need.  Keep in mind that they may be motors in your neighbor's homes.

 

If you're in a rural setting with miles between you and the step down pole transformer, never mind.  10-12 volts even in 500' is okay.

[bankruatsteve]

I have pretty much the same but on high voltage (238-250).  I bought an "AVS" at Global (for me a 7.5KVA works) and it does the job keeping output voltage between 217-229.  

[gdhm]

Thanks for input Guys.   Interestingly, since the last power cut (advised to be a Transformer issue) readings seems higher than 10 day + ago when I checked voltages inconsistently.

Maybe a transformer was on its way out and was the cause of lower voltage levels (especially at night) or they have upgraded the failed one. when we had our power I'd say 2 out of 3  houses in our road were affected and other sois around us and houses backing on to us were not affected at all.  Took them nearly 3 hours to get us back on power (they said they had a lot of jobs to do (a storm night). To be honesty I never know whether helplines are giving us informed accurate info or blanket responses.

 

Crossey

Looks like current levels are not to be worried about (except that they are getting lower each year). My main concerns are Fridges, Freezers and Air Cons which in my experience so far prefer closer to 220V as a norm. I not only find them less effective when voltages are lower (for example a fridge I have has it thermostat currently set to max. It is full of water bottles. A year ago they would all turn to ice or very close to that on max setting. Butter would be solid BUT that is not currently the case.  Our 9 year old Hitachi Fridge/Freezer has recently had its Starter & cut out components fail (I know these are quite common failures in older FF's) but after fixing those, the thermostat parts failed  6 weeks later. So far the Compressor is OK, but I have to wonder if the first 1 to 1½ years of very poor voltages and variations took its toll. Additionally our most used Panasonic Air Con in my bedroom (10 hours a day) gets through fan motors every 1½ years and start getting noisier after only 6 months from new.  My son's Air Con (also a Panasonic) was uninstalled from our family's home and reinstalled in our home and is 2 year older . (not only that but I broke some fans blades and glued back again  9 years ago and it has never needed its fan motor replacing and it remains silent (even though used 8 hours a night). I'm not sure if the fan is unbalanced in my Air Con or whether the variable voltages in the early years in our home have somehow unevenly worn some part(s) and the repairers only repair the consequential damaged motor (but never the root cause as well).

 

Anyway that is mainly why I worry about voltages getting too low. Together with our water Pump that is not reliable if Volts get near the 170s.  TVs, PCs etc. all seem to cope well, as do ELECTRONIC Lighting Ballasts when voltages are less than desirable.  I am sure however lower volts cause higher electricity bills becuase Air Cons and Fridges, freezers have to work harder and longer.

 

 

Impulse,

We live in Khon Kaen, Tambol Naimuang, Amphoe Muang not a rural or village area.

 

Not sure of the ramifications you refer to.  I have never notices any unusual warming of Wiring in our home or any sign of overheating.

With regard to voltage drops all I can say is that as long as I have been in Khon Kaen at different places (Rental, family home initially, and last 10 years in our current own home I have ALWAYS found water heaters & Air Cons especially) and other large wattage items (e.g 1500W items) knock voltage down almost immediately.  (except in year 1 and  2, after we had our new lines installed when the voltage drop I think was much less.  I am no expert but my impression is that the Power lines are operating near their maximum capability to cope with 220V with average loads. Any additional loads (e.g. at night when demand is of course higher causes drops when items like Air Cons are switched on.  I believe the power lines are pretty much extended to capacity because when new and for 2-3 years after normal non peak volts were 225V to 235V and usually just above 230V.  Night with 2 Air cons on still did not shunt the Volts lower than around 212V min.  NOWADAYS 220V is the max and 186V the min.

Currently (8pm) with 2 Air Cons on its 206V (which is quite good since the transformer was fixed about 10 days ago after a power cut.  Before then we were down to around 186V at this time of night 20:20pm  **UPDATE at 9pm its dropped to 198V (boy do I take long time posting ).

When we had insufficient power back in 2008/2009 we had issues with our Water pump. It randomly (we thought) failed to switch on/or off at times. For a while we thought the New Pump was to blame but  later became aware the low voltage on some nights dipping to around 167V was the trigger cause.  We have not had any pump issues since the extra power lines were installed in Dec 2009.

 

My wiring is only 10 years old and gauge and specifications are based on info from Crossey and others on ThaiVisa and my own investigations. Most of the wiring is grounded.  Very heavier duty items Air Cons, electric oven two water heaters are on their own separate fuses and cable is suited to appliance.

 

I say most of my wiring is grounded is because the electrician took it upon himself to assume (goodness knows why when he was told by me ground EVERYTHING) internal lighting did not need grounding.

He was lost for words when I asked him via my wife how come the metal recessed lights had a ground terminal on them.  Still not grounded, as I have no idea how to easily do that after house fully built. I was NOT happy with him.  But I did check EVERY outlet and showers and water heater and all those WERE Grounded.

 

My apologies if I have not answered something asked of me.

 

EDIT: Just seen your post bankruatsteve.

I have never had higher than around 235V so high voltages (at least) are not an issue for me. I'm pleased for4 you the AVS is doing its job to your requirements.

 

 

 

[carlyai]

Maybe you could investigate an Automatic Voltage Regulator.(AVR).
You would need to look closely at the specifications to see if it could improve the 208V condition.
We've had AVRs in our place for the last 2 years. In the house we don't notice them, fans, electrics all seem good, but when I go out the back I can hear them working away.

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[Crossy]

An AVR/AVS like bangkruatsteve has should fix your longer dips and give you a constant 220V, the short term flickers won't be affected as the AVR won't react quickly enough so you will likely still see the UPS switching.

 

They usually boost down to about 160V before running out of regulation. There are a couple of threads on the beasts with costs and effectiveness, try a forum search.

[ksamuiguy]

Here on Samui almost all Low Voltage issues are caused by to much load on the distribution transformer. That and unbalanced loads as evidenced by Transformer failures, they blow up.

 

[The Deerhunter]

I am interested in this as we have problems with our fridge temp settings as and I suspect fluctuating line voltages.  I can sometimes hear the aircon motor "swooping." 

 

How much do AVS or AVR's cost and how easy are they to install.  Do you put them in at where the line enters the house, or before or after an  RCD (Safety Cuts) ??   I assume they have a big battery to even out the current flow, sort of like a big UPS.  

[bankruatsteve]

3 minutes ago, The Deerhunter said:

I am interested in this as we have problems with our fridge temp settings as and I suspect fluctuating line voltages.  I can sometimes hear the aircon motor "swooping." 

 

How much do AVS or AVR's cost and how easy are they to install.  Do you put them in at where the line enters the house, or before or after an  RCD (Safety Cuts) ??   I assume they have a big battery to even out the current flow, sort of like a big UPS

I bought a 7.5 KVA AVS at Global for B7400.  That will handle up to 35 amps.  Easy to install.  Just connect your mains to 'input' and connect 'output' to your CU where the mains used to connect.  Global is the only "Home" place that carries an AVS in my searching.  It uses a transformer to adjust voltage.  I'm pretty sure it is a stepper type versus variable as it will sink into a voltage (for me varying between 217 and 229) and then stay there until something changes and that is probably the input voltage.  BTW my issue is with high voltage (238 - 255).  In use for several months now and no longer hear the "sounds" of voltage where it shouldn't be.

 

Oh, you will need to get some terminals (forget the term) as the connect is over a threaded bolt.  And they are heavy so plan on floor or table to support.

 

 

[billd766]

I live out in rural Khampaeng Phet where power outages happrm once or twice a week.

 

The UPS that I use for my computers is reading 221V at the moment and it varies from about 217 up to 228 volts which is OK.

 

When we built the house some 13 or 14 years ago the nearest house on one side was 500 metres away and 750 metres the other way and the water and electricity supplies were more than adequate. Now there is no more room to build any more houses. Two places that were built are resorts.

 

The PEA don't seem to have upgraded the single phase network though 3 years ago they ran a 3 phase network above the single phase and one resort is hooked into that. the resort also had to buy a 3 phase to single phase transformer as when it was built it was wired up as single phase..

 

I wish that the PEA would upgrade the single phase transformers to handle the extra loads.

[carlyai]

They do have AVRs/AVS at Muan Thai Outlet or Bangkok Outlet. The only place I know is in Roiet, but they may have a Bangkok place.
Main Thai Outlet is mainly a shop for Entertainment electronics: huge speakers, small speakers, build your own speakers, amplifiers, microphones, and outdoor portable/mobile sound systems.
They have everything for the mobile 10000db noise systems, including diesel gensets, UPSs AND AVRs.

So if you can find a sound (= distorted noise) shop, they will probably have AVRs as well.
If you go down the AVR route, get the servo controlled ones not the manual adjust ones.@Naam but another brand, better quality I think, but he seems to have gone into hybanation at the moment, or maybe he could show a pic of his beautiful machine.

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[carlyai]

I am interested in this as we have problems with our fridge temp settings as and I suspect fluctuating line voltages.  I can sometimes hear the aircon motor "swooping." 
 
How much do AVS or AVR's cost and how easy are they to install.  Do you put them in at where the line enters the house, or before or after an  RCD (Safety Cuts) ??   I assume they have a big battery to even out the current flow, sort of like a big UPS.  

They do have AVRs/AVS at Muan Thai Outlet or Bangkok Outlet. The only place I know is in Roiet, but they may have a Bangkok place.
Main Thai Outlet is mainly a shop for Entertainment electronics: huge speakers, small speakers, build your own speakers, amplifiers, microphones, and outdoor portable/mobile sound systems.
They have everything for the mobile 10000db noise systems, including diesel gensets, UPSs AND AVRs.

So if you can find a sound (= distorted noise) shop, they will probably have AVRs as well.
If you go down the AVR route, get the servo controlled ones not the manual adjust ones.[mention=35218]Naam[/mention] bought another brand, better quality I think, but he seems to have gone into hybanation at the moment, or maybe he could show a pic of his beautiful machine.

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[carlyai]

Wooops

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[bankruatsteve]

2 minutes ago, carlyai said:

If you go down the AVR route, get the servo controlled ones not the manual adjust ones.

Uhm, if it is manual adjust it wouldn't be an Automatic Voltage Regulator/Stabilizer.  :)

[tryasimight]

31 minutes ago, billd766 said:

I live out in rural Khampaeng Phet where power outages happrm once or twice a week.

 

The UPS that I use for my computers is reading 221V at the moment and it varies from about 217 up to 228 volts which is OK.

 

3 pahe to single phase transformer?When we built the house some 13 or 14 years ago the nearest house on one side was 500 metres away and 750 metres the other way and the water and electricity supplies were more than adequate. Now there is no more room to build any more houses. Two places that were built are resorts.

 

The PEA don't seem to have upgraded the single phase network though 3 years ago they ran a 3 phase network above the single phase and one resort is hooked into that. the resort also had to buy a 3 phase to single phase transformer as when it was built it was wired up as single phase..

 

I wish that the PEA would upgrade the single phase transformers to handle the extra loads.

3 phase transformer to single phase...really??

[Naam]

1 hour ago, bankruatsteve said:

1 hour ago, carlyai said:

If you go down the AVR route, get the servo controlled ones not the manual adjust ones.

Uhm, if it is manual adjust it wouldn't be an Automatic Voltage Regulator/Stabilizer.

there are three kinds of stabilisers. manually, electronically and adjustment by a servo motor turning the coil.

 

[Naam]

input voltage 137, output 213

 

[Naam]

for the record... since i installed the stabilisers about 15 months ago i had only one brown-out. whenever i pass the three "beauties" i am thinking of the many bottles of Singha i could have bought with 95,000 Baht

[RichCor]

18 minutes ago, Naam said:

input voltage 137, output 213

Way to suck the life out of your neighbors' after-hours party, Naam.

[Naam]

1 hour ago, RichCor said:

Way to suck the life out of your neighbors' after-hours party, Naam.

as mentioned it happened only once. a few years ago it was a drama replacing burnt starting relays and capacitors.

[bankruatsteve]

2 hours ago, Naam said:

there are three kinds of stabilisers. manually, electronically and adjustment by a servo motor turning the coil.

Yah, just saying if you have an AVS then it would be an Automatic StabilZer not manual.

[carlyai]

'Uhm, if it is manual adjust it wouldn't be an Automatic Voltage Regulator/Stabilizer.  :)"
Don't try and get me on syntacs or symantics or you'll lose (maybe[emoji11]).
So the sales person says " over here for the AVRs, some are manual and some automatic." Need I say more, Richard?



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[bankruatsteve]

5 minutes ago, carlyai said:

'Uhm, if it is manual adjust it wouldn't be an Automatic Voltage Regulator/Stabilizer.  :)"
Don't try and get me on syntacs or symantics or you'll lose (maybe).
So the sales person says " over here for the AVRs, some are manual and some automatic." Need I say more, Richard?



Sent from my SM-J700F using Tapatalk
 

Years ago, I had a used car salesman tell me that the car would automatically change gears when I put in the clutch and shifted.  That was to my wife's question if it was an automatic.  Cheers.

[carlyai]

for the record... since i installed the stabilisers about 15 months ago i had only one brown-out. whenever i pass the three "beauties" i am thinking of the many bottles of Singha i could have bought with 95,000 Baht

You're back! Beautiful looking machines. Better than my Lion. I feel an upgrade coming when I win the next lottery. 68 is the number.

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[Foozool]

Need a capacitor on line to regulate the voltage. Transformer is a voltage reducer. From high to low voltage, but it does not regulate the voltage. At pick time with many users voltage will drop at the transformer. Only a big capacitor could regulate the voltage and keep it at an acceptable voltage. 

[bankruatsteve]

8 minutes ago, Foozool said:

Need a capacitor on line to regulate the voltage. Transformer is a voltage reducer. From high to low voltage, but it does not regulate the voltage. At pick time with many users voltage will drop at the transformer. Only a big capacitor could regulate the voltage and keep it at an acceptable voltage. 

Huh?  FYI: transformers can and do step down or step up voltage.  No capacitor.

[Crossy]

22 minutes ago, Foozool said:

Need a capacitor on line to regulate the voltage. Transformer is a voltage reducer. From high to low voltage, but it does not regulate the voltage. At pick time with many users voltage will drop at the transformer. Only a big capacitor could regulate the voltage and keep it at an acceptable voltage. 

 

You may wish to explain how a capacitor can stabilise an AC supply.

 

Oh, and Google "variac" whilst you're at it.

 

 

[billd766]

7 hours ago, tryasimight said:

3 phase transformer to single phase...really??

 

I guess so.

 

When they built the resort there was no 3 phase available so it was wired up as a single phase. Now it is hooked up to the 3 phase and in turn down to a single phase.

 

How do I know?

 

Simple my mate paid for the place to be built and I have been there quite a few times as it is only about 60 metres away if I go through my neighbours place.

 

Also if the single phase has a power cut, but not the 3 phase, the resort still has power while we don't. If the 3 phase is down, which means the street lights are out, but the single phase stays up, we have power while they don't and the new street lights are out.

3 hours ago, bankruatsteve said:

Years ago, I had a used car salesman tell me that the car would automatically change gears when I put in the clutch and shifted.  That was to my wife's question if it was an automatic.  Cheers.

 

[Foozool]

4 hours ago, bankruatsteve said:

Huh?  FYI: transformers can and do step down or step up voltage.  No capacitor.

Ok definitely you are right,

whatever you say Mr.