ABB RELION REX640, Техническое руководство, Страница: 1043 / 1960

•
Ng Seq impedance Fw can be set to 50% of the Z
1
tot magnitude of the line 1
which equals in primary ohms 60.4/2 = 30.2.
•
Ng Seq impedance Rv can be set to 50% of the Z
1
tot magnitude of the line 2.
Setting is for reverse fault in parallel line and therefore magnitude is negative.
Thus setting value is in primary ohms -60.4/2 = -30.2.
• If
Characteristic angle mode is set to “Fixed”, then the value for Characteristic
angle setting can be calculated as below.
Characteristic angle = arctan(X/R)
= arctan(60.1/12.6)
= 78.3 deg
(Equation 280)
The setting
Restrain factor is set based on the minimum unbalance loading allowed
in the power system network. In this case 10% unbalance is allowed in the given
example system, hence the
Restrain factor is set to 0.1.
Fault simulation
The phase to ground faults are simulated in the given example shown in
Figure 580
,
the relay is located at the sending end of the line1 and the output is captured for
forward and reverse direction fault.
The phase A to ground fault is applied on the line1 in the forward direction, the Z
2
value is positive as well as exceeds the
Ng seq impedance Fw setting threshold,
hence the
START
output issued, FAULT_DIR indicates the fault in the forward
direction and the
OPERATE
output will be issued after the
Operate delay time
setting has passed as shown in below Figure 581 .
Figure 581: Phase A to ground fault on forward direction
The phase A to ground fault is applied on the line2 in the reverse direction, the
calculated Z
2
value is negative as well as lower the Ng seq impedance Rv setting
threshold, hence the
START
output issued, FAULT_DIR indicates the fault in the
reverse direction and the
OPERATE
output will be issued after the
Operate delay
time setting has passed as shown in below Figure 582
.
1MRS759142 F Protection functions
REX640
Technical Manual
1043