ABB REG670 - Simplified Logic Diagram

7.9.9.6 Simplified logic diagram
Uinj
Rshunt
95% Stator earth fault protection
STTIPHIZ
REX060
REG670
1
I
U
u_i_sef
u_u_sef
X
S
a>b
a
b
K1
K2
U
UN> = 5%
t
tON=0.5s
95% Trip
un
Compare &
Evaluate
ZRef2
ZRef3
ZRef4
ZRef5
SELECT REFERENCE
3
8
2
4
56
7
9
IEC10000325-2-en.vsd
Measured
Z
Bare
Z
Inj
I
Inj
U
N
U
R
f
ZRef1
IEC10000325 V1 EN
Figure 143: Simplified logic diagram for 100% stator earth fault protection
STTIPHIZ
1
The 100% stator earth fault protection function receives amplified injected voltage and current
via the REX060 unit as two voltage signals. (Voltage inputs in the REG670).
2 The phasor of injected voltage U
Inj
and phasor of injected current I
Inj
is calculated by using
special filter from raw samples. Observe that phasors are calculated for the injected
frequency.
3
The complex bare impedance is calculated from U
inj
/ I
inj
.
4, 5 The complex measured impedance is derived as Z
Measured
= Z
bare
* k1 + k2 .
6 The fault resistance (R
Fault
) is calculated from the complex measured impedance and a
selected complex reference.
7 Selection of one (out of maximum 5) Z
Ref
.
8 Fourier filter to derive the phasor of zero sequence voltage at fundamental frequency
9 The 95% stator earth fault zero sequence over voltage function must operate in parallel with
STTIPHIZ.
1MRK502052-UEN B Section 7
Impedance protection
317
Technical manual