Given an electric power plant (hydro energy) that currently has just an analog indicator for how much power (kilowatts) is generated, which components would be needed to measure the generated power digitally in real time and take that measurement into something like an Arduino and/or Raspberry Pi so that I can log the values over time in custom software?
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\$\begingroup\$ An example would be a Campbell data logger with with relevant sensors voltage, current, phase angle or power factor etc... \$\endgroup\$– Solar MikeJul 30, 2017 at 17:32
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\$\begingroup\$ Do you want to use the analog indicator or do you want all measurement hardware? \$\endgroup\$– Jeroen3Jul 30, 2017 at 19:40
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1\$\begingroup\$ Power can vary second-to-second, do you want ONLY the instant power on one-hour intervals? Do you want energy-meter (integral over time of power) information? Energy meters do NOT sleep between sample times. \$\endgroup\$– Whit3rdJul 31, 2017 at 0:46
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\$\begingroup\$ "has just an analog indicator" - It may be easiest to tap the signal that drives the indicator and measure that instead of building equipment to measure kiloWatts. \$\endgroup\$– JimmyBJul 31, 2017 at 11:58
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which components would be needed to measure the generated power digitally in real time and take that measurement into something like an Arduino and/or Raspberry Pi so that I can log the values over time in custom software?
To calculate power you need to multiply (in real time) the voltage waveform and the associated current waveform. You need to sample at a fairly high rate in order to accommodate harmonics that may be present in your current waveform. Possibly as low as 1 kHz but preferably higher.
If your powergen system is three phase, depending on how it is wired, you may be able to take two voltage waveforms and two current waveforms into your digital system via analogue to digital converters.
Worst case is 3 phase and a neutral - you'll need three voltage ADCs and three current ADCs.
You use a voltage transformer to provide a low voltage (and isolated) AC representation of the voltage and you will probably use a CT to get a safe signal.
Use simultaneous sampling analogue to digital conveters (to avoid any incurrence of a phase angle error), multiply the relevant signals together inside your digital system to get an instantaneous power waveform then average that waveform to get average power.
Output that average power value in a way suitable for the target logging system. You can choose digital or analogue for this method but I would choose a digital comms method.
answered Jul 30, 2017 at 20:23