Mains Voltage Supply Monitoring

RE: Mains Voltage Supply Monitoring

shabaz — Thu, 14 Jul 2022 12:40:31 GMT

There was a mains outage today, it covered a large portion of the town (49 postal codes!).

Anyway, even after an hour or so, the mains voltage is still not fully recovered, it is slightly lower than usual.

I took a few captures using this project, with an ADC connected to the Pi (using an ADC board reviewed here), about an hour after some electricity returned, I didn't capture the precise time unfortunately.

By chance I caught a very noticeable fluctuation in the mains voltage. Y-axis is volts:

The only reason I decided to capture the mains was because the electric fan sounded strange, it had a louder-than-normal whine from its motor (presumably an induction motor) that was very noticeable at its slowest setting.

I've placed CSV files of a few mains captures that I took about an hour after the outage, in a file called mains_data.zip in case anyone ever wants to explore such a thing (I have not looked in any more detail than this). The captures are for 5 and 30 seconds, there are several files in the zip folder, and they were captured in the order that they are named, i.e. the file c1 was captured before d1. The sample values in the files need multiplying by 1880 to see the actual values in volts.

The chart above is drawn from the file c1.

RE: Mains Voltage Supply Monitoring

neuromodulator — Wed, 25 May 2022 16:31:37 GMT

Very interesting. Have you tried to time the waveform? In the old times synchronous clocks synched to utility frequency, which was controlled so that in the long run stayed constant. If we take the AC signal as a clock signal it would be interesting to see how it drifts from the ideal frequency. It also would be interesting to see how the waveform looks if you plot it overlapped like in an eye diagram.

RE: Mains Voltage Supply Monitoring

michaelkellett — Wed, 25 May 2022 08:52:56 GMT

Good idea if you need to measure mains often. Design looks good but is 100% dependent on the £0.41 transformer for safeness [emoticon:c4563cd7d5574777a71c318021cbbcc8]

Have you a way of testing it - I have a 1000V DC tester but that's about the minimum - for a test box you should probably test right up to transformer spec (on the basis that if it doesn't meet its spec then it may have a fault which might get worse.).