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3.2.1
Effective (RMS-) values
Calculation of the RMS values is calculated every half period over a complete period (20 ms @ 50 Hz or 16,66 ms @
60 Hz).
This consists in summing up the squared input voltage values and taking the root of the result, as per the equation:
Here, P stands for the number of samples. For a sampling frequency of 10 kHz and a network frequency of 50 Hz, P =
100.
3.2.2
Flicker
Calculation of the flicker proceeds according to the description of a flicker meter in the standard EN 610000-4-15
(IEC868). However, the entire structure has been replicated completely digitally, i.e. as a component of DSP
program. Flicker calculation is performed at a sampling rate of 100 Hz. This means that the values arrive at the
classifier at a rate of 100 Hz.
The flicker calculation's input signal is the squared mean value from the RMS-value filter. Block 3's weighting filter
(see standard) can be realized completely correctly by digital signal processing. Switching between ranges isn't
necessary, since calculation is performed with 32-bit Floating-Point numbers. Scaling of the output signal to the
means value of the input voltage (Block 1) comes after the weighting filter.
The classifier at the end of the chain (Block 5) computes P st . The classifier's operating range is
10, the error limit of 5 % is adhered to.
Note
If there are very strong amplitude fluctuations which would cause a value of P
the tolerance of 5% is no longer assured. In this case, the error cutoff depends on the
characteristic curve's interference and can range up to 12%.
Introduction
Power Quality Recorder SICAM Q80 7KG8080, System manual
E50417-H1076-C420-A2, Release 12.01.2015
13
20. Up to a P st
greater than 10,
st
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