These sequence component quantities are very useful in that they can be measured and used as
operating parameters to help safeguard equipment. Proper management of the power system conserves
resources and minimizes potentially harmful exposure to the public and operating personnel.
Using symmetrical components, we can say the following about phase currents:
(see the associated figure)
I
a
= I
1
+ I
2
+ I
0
I
b
=
2
I
1
+
I
2
+ I
0
I
c
=
I
1
+
2
I
2
+ I
0
where
is an operator equal to 1.0
120
o
.
From this we can derive that the equation for negative-sequence current I
2
,
is
I
2
=
1
/
3
(I
a
+
2
I
b
+
I
c
)
Under balanced conditions, this value would be zero. If a single-phase input is applied, then a negative-
sequence quantity will appear to the relay. If we let I
b
= I
c
= 0
,
then, I
2
= I
a
3 .
Time Overcurrent (51)
Pickup and Dropout Verification (51/151/251/315/451)
Purpose:
To verify the accuracy of the operation of the 51/151/251/351/451 elements.
Reference Commands:
SL-51/151/251/351/451, S<n>-51.
Step 1:
Connect a current source to Terminals A3* and A4 (A-phase Input 1).
Step 2:
To initially prepare the x51 elements for pickup and dropout testing, send the commands in
Table 13-50 to the relay.
Table 13-50. 51/151/251 Time Overcurrent Test Commands
Command Purpose
A= Gain
access.
SL-N=NONE
Zero out custom logic settings/overwrite with logic =
None settings.
Y Confirm
overwrite.
SL-N= 51
Name custom logic for this test.
SL-51=1,0
Enables 51P/51N/51Q, CT Input 1.
SL-VO1=51PT
Enables OUT1 to close for 50P trip.
SL-VO2=51NT
Enables OUT2 to close for 51N trip.
SL-VO3=51QT
Enables OUT3 to close for 51Q trip
SG-CT1=1,WYE,NA,0
Input 1 ctr = 1, ct = wye, xfmr= na, no grd source.
SG-TRIGGER=51PT+ 51NT+51QT,51PPU+
51NPU+51QPU,0
Enable 51PT+51NT+51QT to log targets and trigger
fault recording
E Exit
Y Save
settings
Step 3:
Transmit to the relay the appropriate row of the setting commands S0-51P from Table 13-51.
With the HMI, you may also go to the front panel interface Screen \PROT\SG0\51\51 and edit
the 51P, 51N, and 51Q settings.
Table 13-51. Time Overcurrent 51 Element Test Settings
Sensing Input Type
Phase
Neutral
Negative-Sequence
1 A
S0-51P=1.0,0.5,I2
S0-51N=1.0,0.5,I2 S0-51QN=0.33,0.5,I2
5 A
S0-51P=5.0,0.5,I2
S0-51N=5.0,0.5,I2 S0-51QN=1.67,0.5,I2
13-60
BE1-CDS240 Testing and Maintenance
9365200990 Rev F
Summary of Contents for BE1-CDS240
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