Troubleshooting regulated voltage from an UPS

[GoatZero]

Allright i was working in my PCBs and i noticed a little  (maybe ) problem i have had this voltage regultor/UPS for around 7 years now, i have replaced its batteries twice now, however lately i have been hearing the internal relay quite often, especially  during nights, so i decided to get to the bottom of this

If power goes out, battery kicks in, so that part its working ok

I went for my multimetter to meassure AC from the "protected" outlets of the UPS, and heres what i found out

Voltage from the protected outlets goes from 124v to 128v and it is exactly that moment when the voltage changes that i can hear the relay activate, the same happens with any other outlet from the house

the voltage fluctuates between these 2 readings every 2-3min or so

I will take more readings during the day, to try to confirm its not regulating however while its still night here come some questions

1) why is voltage higher during the nights?

2) Shouldnt the UPS put out exactly 127v at all times? even if the outlets voltage its 128?

3) In case of being broken , whats the part that dies that makes this not regulate, is it the LM-regulator inside the thing? id it died other components can be also considered dead? could i replace them and make the whole thing work as intended if thats the case?

[Jon86]

So there's only 4v difference? I cant see that being a problem...
What's the normal mains voltage?

[GoatZero]

normal = 124-127

however i thought the point of a voltage regulator was to "regulate" the voltage and keep it steady

[SeanB]

Your UPS has line regulation built in, and is compensating for either high or low mains voltage on the input. Doing the job correctly, the issue is with your grid supplier, as the voltage is higher at night I would suspect the area load has increased and they are running the feeder at full load part of the day now, leading to low mains voltage which the UPS is correcting as it is designed to do.

You would have to monitor the mains voltage for a week or so and report to the supply company that you are getting low mains. They then would place a monitor and correct it if possible.

UPS voltage regulation is by using taps on the internal transformer to either add a few volts or subtract a few voltas from the output, depending on the voltage on the input to get the output within a range. Typically you have 2 taps of around 5V that are added or subtracted so it can compensate for around a 20V variation of input voltages without turning the UPS inverter on and warning you of a power failure or a brown out.

[Lurch]

the issue is with your grid supplier, as the voltage is higher at night I would suspect the area load has increased and they are running the feeder at full load part of the day now

More than likely the other way around, higher voltage at night when everything is off load, like a cheap power supply.

[Dantali0n]

the issue is with your grid supplier, as the voltage is higher at night I would suspect the area load has increased and they are running the feeder at full load part of the day now

More than likely the other way around, higher voltage at night when everything is off load, like a cheap power supply.

Statistics from my country have shown the other way around though, turns out everyone runs their dishwasher and laundry machine at night. So power demand atleast in my country is higher at night.

I was looking for the report of the power company but unfortunatly couldn't find it anymore.

[con-f-use]

Statistics from my country have shown the other way around though, turns out everyone runs their dishwasher and laundry machine at night. So power demand atleast in my country is higher at night.

I'd like to see those statistics. Power demand is always higher at daytime. Most people work during the day. That is the time when heavy machinery, office computers and all the power consuming equipment is used. Consumption usually spikes in the morning, at lunch-time and dinner time. You must have gotten that confused (see picture - source: "Energieonderzoek Centrum Nederland").

[Dantali0n]

Took me a while but I found it:


Original source: http://www.tennet.eu/nl/nl/nieuws/article/tennet-levert-real-time-verbruiksgegevens-voor-actie-1010.html

Seems you where right, Although peak usage is highest just before night but that wasen't the point.
Probably mistaken because of the angle.

[GoatZero]

Im certainly not meassuring all week, but maybe i will.... meassuring the outlet right now (daytime), and its going in a steady 123.5v-125v

 the relay its not tripping at all so, in the end i can consider this that in the night is more about the company transformer and people in the city not using electricity thats why i get some spikes that make my voltage regulator attemp to stabilizae the voltage??

Shouldnt be safer to put down the breakers at night just to make sure nothing gets damaged during the nights or ths can be considered normal?

[SeanB]

That is normal, at night lower load and slightly higher voltage. Nothing much you can do other than complain to the utility if you consistently get high mains at night outside the tolerance of the supply.

[Lurch]

Shouldnt be safer to put down the breakers at night just to make sure nothing gets damaged during the nights or ths can be considered normal?

Your voltage is extremely stable. The utility company will have different targets and specifications but ±10% isn't unusual so until it goes outside these figures the utility company won't be that interested. A couple of volts is not worth worrying about.