ABB Relion REG670, Техническое руководство

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openCircuitLimit
Open Circuit
Hysteresis
0
no open-circuit open- circuit
Open- circuit
characteristics
IEC11000073-1-en.vsd
Z
Measured
{ } re
IEC11000073 V1 EN
Figure 141: Open circuit characteristics
Blocking : The output OPCIRC is blocked during an error occurring and during
initialization of function.
Detailed Set: If the total measured real part of the impedance is greater than the setting
OpenCircLim the output OPCIRC is TRUE, see figure 128 .
7.9.9.5 Measuring reference impedance
The healthy impedance is equal to the parallel connection of the neutral point resistor
(
R
N
), the capacitive reactance between the stator windings and earth (1/ω C
stat
) , the
transformer magnetization impedance ( Z
mT
) and the earth fault resistance ( R
f
). The
series resistance in the injection circuit is eliminated by k2 . R
f
is very large in the non-
faulted case and the measured impedance is equal to the stator reference impedance:
1 1 1
stat
ref N mT
j C
Z R Z
w
= + +
EQUATION2502 V1 EN
Where
2
inj
f
w p
= ×
EQUATION2503 V1 EN
The injected frequency f
inj
of the square wave, is a set value, deviating from the
fundamental frequency (50 or 60 Hz). The injected frequency can be set within the
range 50 – 250 Hz with recommend value 87 Hz in 50 Hz systems and 103 Hz in 60
Hz systems.
The reference impedance can vary depending on the operational state. The reason for
this can be the following:
Section 7
1MRK502052-UEN B
Impedance protection
312
Technical manual