How much PEA supply Voltage is too much?

[gdhm]

I posted on another thread a few days ago about a breaker tripping but am making a new post as this is unrelated (but came to light whilst trying to resolve tripping breaker).

I have noticed during 3 days of testing at times of lowest consumer usage (my area around 10am - 11am weekdays) that my supply previously around 226V to 234V is now ranging between 274V and 283V( this morning) on my multimeter and I am concerned this is much too high a supply voltage. Night time (after peak usage period drops to around 236V - 245V (10pm)

Possibly salient: about 4-6 weeks ago something happened to our immediately local sois power supply around 5:30pm with lights becoming much brighter and fans speeding up. People came out of their houses asking others if they were experiencing the same, and they were). Within about 5 minutes (thankfully) the streets power supply was cut for around 40 minutes. Before it cut out I managed to take a multimeter reading and it was 346V approx.

When the power supply came back on line I took a new reading and it was 283V approx. and I thought all is OK. However, now thinking about it, that was during normal peak usage time 6:15PM approx. and with power off for 40 minutes people probably used more than normal peak time electricity catching up, running air-cons etc.

I have 4 short questions.

Assuming multimeter is not faulty (no reason to think it is)

1) What is an acceptable MAXIMUM normal safe Voltage for a Thailand street supply?

2) If my current (as I type 10:40am Wed) low consumer usage reading of 283V is too high, should I urgently contact local PEA and ask them to check it out urgently and deal with it?

3) Are these highs a sign of a faulty street transformer (or what)?

4) How much damage (if any) to wiring and/or appliances could be caused with peak periods of several hours maybe of around 282V? may be for several weeks without me realizing the problem?

Many thanks

Edited September 18, 2013 by gdhm

[gdhm]

Update now 287V at 12:00 midday (touched 290V (max today 5 mins ago)

[geordieman2]

This is way too much.

Normally the limitys are 10% over and under.

So with Thailand being 220, your voltage should be between 198 and 242 Volt.

Do note that this is 10 minute avreage, meaning the average in a 10 minute period cannot be outside those numbers, so very short term numbers can be higher or lower, as long as the average over 10 minutes remains within the 10% margin.

The voltage you are getting (if correctly measured) can and will cause permanent damage to a lot of equipment.

You are getting a constant 30% overvoltage which is way too much.

Indeed, best to contact PEA asap.

Damage to wiring is highly unlikely, but damage to your appliances is a much higher likelyhood.

Most electronic equipment can handle a pretty high overvoltage for short periods of time, and they can handle the 10% overvoltage virtually indefinitely.

Do get your multimeter checked out though, because at 346 Volt, even if only 5 minutes, there should be a decent amount of damage to equipoment. I doubt any regular lightbulb will last much more then 10 or 20 seconds at that voltage, and electronic equipment (think power supply for laptop etc) is usually protected internally by MOV's, small things designed to protect against very short high spikes on the supply, but at sustained high voltages they simply burn out. If you're lucky there's a fast blow fuse protecting the device, but often the whole thing will be burned...

[Crossy]

My cheap Chinese multimeter reads high on AC when the battery gets low but before the low-batt indicator comes on.

Replace the battery before calling PEA just in case.

[gdhm]

Thanks geordieman2 & Crossy

Firstly, geordieman2.

Thank very much for this info. I will record it and know what's OK/not OK in future. Some may think info passed on goes in one ear and out the other with some poster - BUT NOT WITH ME. If I feel I may need info or will not remember I write notes in my PC for future reference.

You are correct at high voltage damage but surprisingly some lights seem to cope with a few minutes of very high voltage. I base this observation from when I was in Spain on a new/being built private Urbanization. We had a builders supply fault one night at 2am (I was luckily still awake) The Volts went well over over 400V and my lights seemed twice as bright, and fans racing. I switched everything off as fast as I could, but a few lights must had been on several minutes (2am in morning). I thankfully had no obvious immediate damage (but possibly unknown longevity damage). A few others suffered destroyed air-cons, fridges and mostly lights as you suggested. Luckily most were asleep and had most appliances switched off.

geordieman2 you were correct to query my readings or multimeter. Although my readings were taken correctly the multimeter reported incorrectly.

Crossy hit the nail BANG on the Head with:

My cheap Chinese multimeter reads high on AC when the battery gets low but before the low-batt indicator comes on.

Replace the battery before calling PEA just in case.

What can I say Crossy , YOU REALLY ARE THE MAN!!! (but I already knew that). Thank you (again) ever so much.

I only wish you lived in Khon Kaen because I sure could use an electrician like you (purely from my selfish point of view I might add- I am sure you are happy where you are). To be honest not being able to locate a good electrician. I have at last found a decent plumber who seems to know his onions.

2 days ago I had left my Multimeter on in its case (rare must be getting senile). I still worked and I noticed a battery sign was showing. I was not sure if always there but replaced the battery (now 5.6V).

The replacement (a reserve I had with expiry date 8/2014) ALSO showed the battery symbol but I thought Voltage 8.%V was OK and mistakenly thought the symbol was always there and may be blinked if battery too low (need to find manual) I also noticed I have blown at sometime an internal 315ma fuse (obviously it is not needed for what I check (intentionally ) check continuity, Ac volts and batteries.

I luckily had another newer 9V battery and after reading your post I put that in the multimeter and it works and battery sign has gone.

I retested my voltages and found that you were bang on as to why why I may have had high readings!!

Now my readings are:

At t 5:15pm were 222V Live and 4 Negative. I was very happy I can tell you as that is normal for us.

At 6:00 pm (well into Peak use time) and it had dropped to 206V Live & Neutral had risen to 6V as it usually does for our house as Live drops (I am sure you understand technical reason).

At 6:15 it was 216V Live and still 6 V neutral.

At 6:30pm it was 219V live and 3 - 4 V Neutral (as you can see the small volts on Neutral to Ground lowers to a minimum 3 or 4 as Live rises to normal levels

Anyway Crossy, bottom line ALL IS OK

I own a UNI-T UT33D Multimeter cost me ฿460 in Dec 2006. (I keep financial records (sad person aren't I?). I need to get another fuse and have broken the rest so I may decide to buy a new model. Do you or geordieman2 know if UNI-T is a reasonable Brand or do you have a better recommendation I can readily get in Thailand. I know prices have gone up. No point in laying out out to much for features I do not have the skills/requirements to use BUT reasonably reliable readings are important for those I do use (namely DC battery Voltage, Continuity, AC Voltage, test for Live, Neutral & Ground).

Are there additional features you feel desirable or may be useful to me in future.

Regards to you both and again thanks for you time and help. Another successful resolution

[Litlos]

I also have a Uni-T bought from Amorn for about 300Baht. Not sure of the model but also has a thermal detector which is handy for the air conditioner testing. I suspect the blown fuse in yours is for the amps reading, which you will probably not use anyway. There is an Amorn in KK from the look:

http://www.amorngroup.com/en/branch.php

Is interesting about the readings being wrong with a low battery on the Chinese made multimeters, will have to watch for that one. Just wish they would let me bring my work multimeter home as is a Fluke 789, and I know these do not give faulty readings, but at about 25,000Baht one should hope it is accurate and reliable.

Cheers