Schweitzer Engineering Laboratories SEL-251D-1, Instruction Manual

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7-14 Maintenance and Testing Date Code 940518
SEL-251D-1 Instruction Manual
51GP
Ground/Residual time-overcurrent element pickup
50G
Ground/Residual definite-time overcurrent element pickup
51NP
Ground/Residual time-overcurrent element pickup
50NL
Ground/Residual definite-time overcurrent element pickup
50NH
Ground/Residual instantaneous overcurrent element
Method: 1.
Using the SET command, set the desired programmable output (A1-A4) to
follow the appropriate overcurrent element. Select one of the overcurrent
elements from the first row of the Relay Word listed above.
2. Disable all external and internal torque control on the overcurrent elements.
Using the SET command, enter NA for the ETC(1) and ITC(1) settings. These
settings specify the overcurrent elements in Relay Word row R1 you want
externally and internally torque controlled (none in this case).
3. Apply current to one phase and observe the pickup and dropout of each element.
Record the results.
Note:
With current applied to only one phase (e.g., I
A
= 6 A, I
B
= I
C
= 0),
the following zero-sequence current results:
I
0
=
13
[I
A
+ I
B
+ I
C
]
=
1
3
[6 A
A
0
0
+ 0 A
A
0
0
+ 0 A
A
0
0
]
= 2 A
A
0
0
The ground/residual overcurrent elements respond to 3xI
0
current. Thus, for this
test all overcurrent elements see 6 A.
'(),1,7(7,0(29(5&855(17(/(0(177,0,1*7(676
Purpose: Verify operating times for the following definite-time overcurrent elements.
50LT
Phase definite-time overcurrent element
50GT
Ground/Residual definite-time overcurrent element
50NLT
Ground/Residual definite-time overcurrent element
Method: 1.
Disable all external and internal torque control on the definite-time overcurrent
element pickups in Relay Word row R1. The above definite-time overcurrent
elements are derived from their respective pickups in Relay Word row R1. If
one of these pickups in Relay Word row R1 is torque controlled, the respective
definite-time overcurrent element it drives in Relay Word row R2 is also torque
controlled.
Using the SET command, enter
NA
for the ETC(1) and ITC(1) settings. These
settings specify the overcurrent elements in Relay Word row R1 you want
externally and internally torque controlled, respectively (none in this case).