2 Functions
118
7SD5 Manual
C53000-G1176-C169-1
2.5.1.3
Calculation of the Impedances
A separate measuring system is provided for each of the six possible impedance loops
L1-E, L2-E, L3-E, L1-L2, L2-L3, L3-L1. The phase-earth loops are evaluated when an
earth fault detection is recognized and the phase current exceeds a settable minimum
value
Minimum Iph>
. The phase-phase loops are evaluated when the phase current
in both of the affected phases exceeds the minimum value
Minimum Iph>
.
A jump detector synchronizes all the calculations with the fault inception. If a further
fault occurs during the evaluation, the new measured values are immediately used for
the calculation. The fault evaluation is therefore always done with the measured
values of the current fault condition.
Phase–Phase
Loops
To calculate the phase-phase loop, for instance during a two-phase short circuit L1-
L2 (Figure2-33) the loop equation is:
I
L1
· Z
L
–
I
L2
· Z
L
= U
L1-E
– U
L2-E
with
U,
I
the (complex) measured quantities and
Z = R + jX
the (complex) line impedance.
The line impedance is computed to be
Figure 2-33
Short-circuit of a phase-phase loop
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Страница 2: ...2 7SD5 Manual C53000 G1176 C169 1 w w w E l e c t r i c a l P a r t M a n u a l s c o m ...
Страница 4: ...4 7SD5 Manual C53000 G1176 C169 1 w w w E l e c t r i c a l P a r t M a n u a l s c o m ...
Страница 18: ...Contents 18 7SD5 Manual C53000 G1176 C169 1 w w w E l e c t r i c a l P a r t M a n u a l s c o m ...
Страница 34: ...1 Introduction 34 7SD5 Manual C53000 G1176 C169 1 w w w E l e c t r i c a l P a r t M a n u a l s c o m ...
Страница 444: ...2 Functions 444 7SD5 Manual C53000 G1176 C169 1 w w w E l e c t r i c a l P a r t M a n u a l s c o m ...
Страница 580: ...4 Technical Data 580 7SD5 Manual C53000 G1176 C169 1 w w w E l e c t r i c a l P a r t M a n u a l s c o m ...
Страница 682: ...Literature 682 7SD5 Manual C53000 G1176 C169 1 w w w E l e c t r i c a l P a r t M a n u a l s c o m ...
Страница 698: ...Index 698 7SD5 Manual C53000 G1176 C169 1 w w w E l e c t r i c a l P a r t M a n u a l s c o m ...