Strange Occurance During Brown Out.

[thaibeachlovers]

Other night, electricity browned out to the point where a filament bulb just glowed. However, the fridge and the tv/ DVD player that were in operation when the brown out started continued working and I was able to see the movie. Nothing that I tried to start would, such as the flourescent lights, although next door had flouro lights on.

Any explanation?

[Daffy D]

I'm sure some of our local electricians will be along with the correct answer in a moment but my guess is that there was just enough juice to keep things that were already running going but most things, including fluorescent, need a extra kick to start and there was just not enough to juice to do that.

As for your neighbors having power they are probably on another phase (think 3 phase) and they were not effected.

Next time it might be the other way round and you can watch Tv while thy are scrambling about with candles.

[lopburi3]

I suspect only the light was working in the fridge but most TV and DVD will operate down to about 90 volts as they are designed to be multi system for 110/220v countries without change. Not all lights are created equal and the new T5 (electronic ballast/starter) will stay bright down to very low voltages. The screw base also work lower than the older tube types and those that are on will likely stay on when trying to start again will not work.

[PhayaoPete]

Not too long ago, we had a total 2 hour blackout during a wind/rain event and when it finally came back on....only one of the three lights out on our gate, came on...they are all on the same curcuit and share the same power. The one lonely bulb glowing, wasn't glowing up to its fullest, but the others weren't glowing at all. Don't know about this one. pp

[thaibeachlovers]

I suspect only the light was working in the fridge but most TV and DVD will operate down to about 90 volts as they are designed to be multi system for 110/220v countries without change. Not all lights are created equal and the new T5 (electronic ballast/starter) will stay bright down to very low voltages. The screw base also work lower than the older tube types and those that are on will likely stay on when trying to start again will not work.

Actually I could hear the fridge motor working.

I would agree that a fluro light might stay on, but not start. However, none of mine were on when the brown out started.

Thanks for the replies.

[Pib]

My moobaan is a combination of homes configured with single-phase or three-phrase wiring. The larger homes have three-phase wiring and the smaller homes, like mine, have single-phase wiring. A couple times a year one of the phases will develop problems so it's not uncommon to see some of the single-phased homes to have no to low power, while other single phase homes (like your next door neighbors) have full power because they are connected to one of the two phases/lines not experiencing any problems.

The power company hooks each single-phase wired home to a different phase/line...I assume around one-third of the single-phase wired homes to each of the three phases/lines available running on the power poles...and of course the three-phase wired homes are hooked to all three phases/lines on the poles. For the larger homes on three-phase power they experience problems in terms of some rooms of the house not having correct/no power...how their home is affected depends on how the three phase wiring was wired-up in the home/fed to each room.

So, beyond what was mentioned in other posts about some items continuing to work since their power supplies can work on approx 90 to 240V, how your moobaan/individual home/building is wired-up/hooked into the probable three phase power on the poles feeding the overall area can have an affect also.

[Crossy]

If your supply voltage gets lower than about 190V then expect things to become erratic.

Incandescent lamps (ordinary light bulbs) will just get dim.

Devices using electronic (switch mode) power supplies will invariably work well outside their design range. These include modern TVs, compact fluorescent lamps, fluorescent tubes with electronic ballasts, PCs generally (but laptops usually have wide range PSUs anyway) and appliances with inverter or VFVV motor drives.

Do remember however, that even if a device continues to function outside its design range you could be placing additional stress on the power supply components. Some (cheap) PSUs will actually self destruct when presented with excessively low supply voltage, they continue trying to operate until the power devices are taken outside their safe operating area and smoke ensues (more expensive designs have protection built in to prevent this happening).

If you experience regular periods of low voltage, get a voltage regulator (stabilizer) for your expensive electronics, small ones are not expensive and will repay your investment in longer life of your kit, combine with quality surge-arrestors for more protection.

We have a 3kVA regulator which powers our large UPS, this in turn works some of the lighting, the home theatre and my PCs. A small gasoline/LPG fueled genset gives us autonomy when the mains actually goes off (and powers the kitchen appliance that are not on the UPS).

[Pib]

I added a 0-300V analog panel meter to the input side of my main circuit panel. It's scale is even marked in black from 0-160V to indicate low voltage, marked in green from 160-240V for acceptable voltage, and 240-300V in red to indicate high voltage. Bought it at an Amorn store for about 80 baht. Don't know if I agree with the lower end of the acceptable voltage...personally, during a brownout I use around 190V as my lower limit "if" the voltage is stable/not varying... and I've never had a problem with with the voltage being above 230V....when operating properly which is fortunately 99.9% of the time here in my Bangkok location it hangs around 225V day or night.

But during that remaining 0.1% of the time which always seems to happen at a bad time, whenever I notice a possible brown-out/power issue I will go look at the meter to see how much voltage is coming in and how much it might be varying. During brown-outs it's not uncommon to voltage levels to vary quite a bit...even to below 50V. Depending on what the voltage level is and how much its varying I will start turning devices off and turning circuit breakers to off also. And where I say turn devices off, if the devices also have a standby mode like most TVs I will turn them off at the power strip/unplug them from the wall....I don't even want them to try to work in standby mode when voltage blackouts or brownouts occur. If the brownout is really bad....that is, really low voltage and widely varying voltage I will even turn off the main circuit breaker after I have turned off all the individual circuit breakers. Sometimes I will usually leave a few circuits on that only feed certain lights depending on the voltage situation if it's night time. Once I see the voltage is stable and back to approx 220V on the panel meter then I will start turning everything back on....first he main circuit breaker, then the individual room circuit breakers, etc.

As Crossy states above brownouts can put a real stress on electronics/electrics. If possible, turn your electronics/electrics off during these periods and once the power does come back on you might want to wait a minute or so for the power to fully stabilize vs the power only trying o come back on which can cause several power surges/spikes which electronics/electrics don't like.

[electau]

Any voltage that falls below 190VAC on 220 V supply should be of concern. You should determine if your installation is the problem or the MEA/PEA distribution. Overloading, and phase unbalance in the HV or LV distribution network may be one of the causes.

[Pib]

Any voltage that falls below 190VAC on 220 V supply should be of concern. You should determine if your installation is the problem or the MEA/PEA distribution. Overloading, and phase unbalance in the HV or LV distribution network may be one of the causes.

It's the MEA....at least the whole moobaan (approx 750 homes) experience the problem...I expect the problem also extends beyond the moobaan...when calling MEA they immediately say they are aware of the problem and it's affecting the who area...but forturnately blackouts and brownouts in my western Bangkok area only happen a couple times per year. However, at least once a week we usually experience a half second loss of power...where the MEA is apparently balancing/switching the load around the area...we can always tell when it has happened if we were away from home or asleep as it only take a split second loss of power to cause our microwave clock to stop working and requiring a reset after the very brief power outage..that been going on since I moved here over 4 years ago and long before that according to our neighbors...but they do say it use to be worst....guess that means it getting better. But when those blackouts/brownouts of several minutes to hours do occur I want to be ready to monitor and minimize their impact on my electronics/electrics.

[lopburi3]

Actually they do have a serious issue with power switching - either they do not try to sync and just turn off and new on or they never get in phase and it trips but often times there is a few second outage here in Bangkok.

But more often the problem in my mooban is one phase of a transformer fuse blowing so that phase gets down to about 50v or lower (always some leakage getting onto it) and other two phase go to about 160v for anything from 30 to 90 minutes it takes for crew to replace fuse.

[electau]

A brownout is a prolonged period of low voltage (sag). A blown HV fuse on a 3 phase transformer will cause two phases on the LV to neutral to be normal (220V) and the third phase to fall to 155V. This phase is the one with low voltage. This is a fault condition.

Earth faults and short circuits on the distribution network must clear in less than 5 secs in fact in a short number of cycles, but auto reclosers on the HV may re-energise after the fault is cleared, generally twice then lock out.

Switching failures and errors cause load shedding and re-energiseation is brought on gradually in increments so as to maintain system stability. Transient faults are often seen as a short dip in voltage,

Long HV spur lines in rural areas have auto tap changing transformers which regulate the 3 phase voltage, they may be situated 20 to 30 km apart.

Most LV problems are within the customers electrical installation, excessive voltabe drop in mains, sub mains and final subcircuits.

When checking for low voltage it should be carried out at the main switchboard on no- load and then on load in increments.

The PEA has a voltage regulation requirement under TIS for +/-10% of nominal 220V. For the MEA it is +/- 7% in Bangkok.

　

Edited January 5, 2013 by electau

[Pib]

But more often the problem in my mooban is one phase of a transformer fuse blowing so that phase gets down to about 50v or lower (always some leakage getting onto it) and other two phase go to about 160v for anything from 30 to 90 minutes it takes for crew to replace fuse.

Ditto for my Bangkok moobaan regarding a fuse on a pole blowing somewhere for only one phase (but usually on the poles for a transformer since most the fuses seem to be located there).. One a few occassions it has been a fuse within our 750 home moobaan but in other cases the problem is outside the moobaan somewhere.

Since I'm a single phase wired home I don't know how much the other phases may be affected since when the problem usually happens is during the day when most folks are at work/school...actually less power being drawn. But on a few times when it has occurred at night where one phase is completely down a person can see lights in three phased wired homes changing brightness in some rooms while other rooms remain at steady lightning....that is, the rooms with the problem phase are varying in brightness indicating the widely varying voltage just as my analog panel meter shows me while rooms with the apparently unaffected phases remain at a steady light level (however, the voltage may indeed be varying significantly but not enough to significantly change the florescent light output). I've never had the chance to check the actual voltage level on the two phases which appear to still be operating properly when power is out/low on one phase. But it wouldn't surprise me to see the voltage levels lower/varying.

But if I had one wish that had to be used to either solve the occasional brownout/blackout or frequent momentary (half second) switching/load balancing of the power in the area the wish would be to solve the frequent momentary power loss that just causes too many power surges which is another reason I have a whole house surge protector and use surge protected power strips. Blackouts/brownouts have a happened occassionally anywhere I have lived on Earth over my years, but since living here in western Bangkok for over four years I have never, ever experienced so many frequent/momentary losses of power from the MEA apparently load balancing....but it has got a little better (less) as each year goes by. The the main reason for my whole house/power strips surge protectors that protect in all three line modes is due to lightning storms that get very nasty during the rainy seasons.

[thaibeachlovers]

Actually they do have a serious issue with power switching - either they do not try to sync and just turn off and new on or they never get in phase and it trips but often times there is a few second outage here in Bangkok.

But more often the problem in my mooban is one phase of a transformer fuse blowing so that phase gets down to about 50v or lower (always some leakage getting onto it) and other two phase go to about 160v for anything from 30 to 90 minutes it takes for crew to replace fuse.

I see that my question has resulted in some interesting facts that I had no knowledge of.

I've only experienced 2 brown outs here, both times after hearing an explosion at a transformer, presumably the fuse blowing up. Definitely not my installation.

I'll remember to turn everything off next time, thanks.

Edited January 5, 2013 by thaibeachlovers

[thaibeachlovers]

Coincidentaly, the night I wrote my previous reply, there was a brownout. That makes 3 now.

[Pib]

Coincidentaly, the night I wrote my previous reply, there was a brownout. That makes 3 now.

As FYI, three brownouts equals one blackout.