Instruction manual
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AQ G3x7 Generator protection IED
141 (211
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The numerical processes apply the simple R-L model.
For the equivalent impedance elements of the measuring loop, the following differential
equation can be written:
If current and voltage values sampled at two separate sampling points in time are
substituted in this equation, two equations are derived with the two unknown values R and
L, so they can be calculated.
This basic principle is realized in the algorithm by substituting the Fourier fundamental
component values of the line-to-line voltages for u and the difference of the Fourier
fundamental components of two phase currents:
R
1
Positive sequence resistance of the measuring loop
L
1
Is the positive sequence inductance of the measuring loop,
L1, L2, L3 indicate the three phases.
The applied numerical method is solving the differential equation of the measuring loop,
based on the orthogonal components of the Fourier fundamental component vectors.The
calculation results complex impedances on the network frequency.
Figure below shows the principal scheme of the impedance calculation Z_CALC.
