Instruction manual
–
AQ G3x7 Generator protection IED
142 (211
)
Figure 3-85: Principal scheme of the impedance calculation Z_CALC
The inputs are:
•
The Fourier components of the three phase voltages,
•
The Fourier components of the three phase currents
•
Parameters
The outputs are the calculated positive sequence impedances (R+jX) of the three
measuring loops:
•
Impedances of the three phase-phase loops,
The calculated values of the Z_CALC module
Z_CALC includes three practically identical software modules for impedance calculation:
•
The three routines for the phase-to-phase loops get line-to-line voltages calculated
from the sampled phase voltages and they get differences of the phase currents.
3.2.23.3
Characteristics of loss of excitation protection function (OFFSET CIRCLE)
The operate decision is based on offset circle characteristics. The calculated R
1
and X
1
=
ϖ
L
1
co-ordinate values of the three measuring loops define three points on the complex impedance