Application Manual - ABB REL650 Applications Manual

Section 3
REL650 setting examples
86
capacitance between the phase conductors and ground and the impedance of equipment
connected between the transformer neutral point and ground. In this network a Petersen
coil parallel with a neutral point resistor is connected to the transformer neutral. The active
ground fault current, that is, the residual current in phase with the residual voltage, is used
for line fault detection. The active residual current only flows on the connection from the
neutral point resistor and the fault point on the faulted line.
1. Set OpModeSel to 3I0Cosfi if the current component is related to the set
characteristic angle relative to the reference voltage, or 3I03V0Cosfi if the power
component is related to the set characteristic angle relative to the reference voltage,
or 3I0 and fi, if measuring the total residual current if the angle fi is within the set
range.
The active ground fault current, out on the faulted feeder, can be calculated by first
to calculate the residual voltage at required sensitivity (fault resistance).
V
Phase
=
V
o
×
3 R
f
+
1
Z
0
GUID-28E30403-2324-4F8E-BC5F-0FCA0D974410 V1 EN
where
= -
Z jX / / R / / j X 3
0 c n
GUID-B1001899-6E4B-4BE6-9C55-0800F736D37C V1 EN
The active ground fault current component can now be calculated according to
V
0
= ×
I I
j ,active Rn
V
Phase
GUID-759EDA57-30C1-42C7-90EC-64F8EA10B1FE V1 EN
where I is the rated current of the neutral point resistor.
Rn
In the network the following conditions applies:
The Petersen coil is perfectly tuned: 3X
The neutral point resistor provides 25 A at ground fault without resistance. This
gives the value of R
13800 / 3
R = =
3187
n
25
GUID-6F86369A-425B-4597-A4FB-1DC0B0D13D3D V1 EN
The zero sequence network impedance works out as:
= -
Z jX / / R / / j X 3
0 c n
GUID-254283ED-CBD6-4BE7-839B-192065CF0815 V1 EN
9 R X X
N N C
=
3
(
n
+ ×
3 X X j R 3 3 X
N C N
= X
n
.
n
W
9 R X X
N N C
=
3
(
n
+ ×
3 X X j R 3 3 X
N C N
1MRK 506 334-UUS A
)
-
X
N C
c
= = W
3 R 9561
)
n
-
X
N C

Application manual

(Equation 26)
(Equation 27)
(Equation 28)
(Equation 29)
(Equation 30)