Instruction manual
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AQ G3x7 Generator protection IED
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Current base harm.
This module calculates the basic Fourier components of the of the phase currents both for the
network side and for the neutral side. The result of this calculation is needed for the differential
characteristic evaluation.
Differential characteristics
This module performs the necessary calculations for the evaluation of the percentage differential
characteristics.
Decision logic
The decision logic module decides if a general trip command is to be generated.
The following description explains the details of the individual components.
Differential current calculation
The differential currents in the phases are calculated as the difference between the currents
measured on the network side and those on the neutral side.
This module calculates the basic Fourier components of three differential currents. These results
are needed also for the high-speed differential current decision.
Principle of harmonic analysis
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The differential currents
The outputs are the magnitude of the base harmonic Fourier components of the differential
currents:
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The the magnitude of the base harmonic Fourier components of the differential currents
These values are processed by the “Differential characteristics” software mo
dule evaluating the
currents according to the differential characteristics.