Debugging Power Quality Problems

Hello. We’re an IT services company helping one of our clients with some power quality problems that’s frying expensive medical equipment. We’re wondering if the IotaWatt could be used to determine which of the five main power quality problems (The Five Main Power Problems | Eaton) are at play here and which circuit it originates on?

For example we had another client that every time they used the microwave it caused their UPS to kick on. Of course, it took us a while to correlate this together and it actually fried their router a couple of times. It was only by luck that we were onsite addressing the problem and we happened to overhear both the microwave and the UPS click on/off that we figured it out.

Hope this makes sense. Thanks in advance.

To be clear, IoTaWatt isn’t a power quality instrument. What it does is measure voltage and power and records the 5 second average, sampling two or more times per second per circuit for up to 14 circuits. The data is stored for years internally and available through a graphical interface and can be uploaded to a time-series database like influxDB.

Looking at the five power quality problems referenced, I would say that IoTaWatt would not be a great tool for the first two - surge/spike and line noise. The last three - Brownout/Undervoltage/Sag, Swell/Overvoltage, and Blackout/Power Outage would be evident depending on severity and duration.

You would be able to identify the circuit if it is one of the 14 being monitored.

The UPS/microwave problem would probably have been recorded as an increase in power on the microwave circuit, and a decrease on the UPS circuit when that kicked in. The graphical output would show these two events happening at the same time, so a trained and suspicious eye could probably pick it up, particularly if it happened regularly.

So if, as a first step you just want to get a picture of the voltage swings, then IoTaWatt could be useful. But to get a handle on the overall quality you would probably need to have a good electrician instrument it with an instrument designed to look at quality rather than quantity.

Thank you for the feedback. We happen to have a couple of electrical engineers on our staff who were attempting to assist with the issue and knew that I had your toolset in my home, personally. I will forward your feedback to them and go from there. You can explain things at a much better level than I can, so I really appreciate your help/input!

Even though data history occurs at 5 second intervals, have you considered the possibility of logging power quality events, like frequency stability and voltage stability? Perhaps you could drop these into a separate log file? This would be super useful if the checked parameters had thresholds we could set. I know things like waveform distortion are too fast to check.

To paraphrase Dirty Harry - A device needs to know it’s limitations. Trying to use an energy monitor as a power quality analyzer is a slippery slope. A fully loaded IoTaWatt at best samples about 4% of the cycles of each circuit. A quality analyzer should be looking at every cycle very critically.

Also frequency is really only of interest if you are managing the electrical network for the whole system, that is the whole state or multiple states. The only way to adjust frequency is to adjust the generators and it is controlled very closley because if it moves even a small amount away from normal then thats a recipe for state wide power outages. Thats bad news.

Thought I would just bump this thread a little. Whatever the sample frequency is, it would be awesome to log events where voltage, frequency or current fell outside of defined limits. Here is what a short power cut looked like during a thunder storm with high winds. It was likely a fault clearing followed by loss of load for a large area which caused a slight surge in voltage when the OCP cleared the fault.

IotaWatt runs on a tiny 5VDC 18650 based UPS so it rides through blackouts recording 0VAC.

My fancy UPS logged 7 seconds of blackout and 12 seconds of bypass AC unqualified (it was not running in bypass mode).

My not fancy UPS says 2 seconds of utility power failure.