Ground Current Accuracy; 50:0.025 Ground Accuracy Test - GE 239 Instruction Manual

CHAPTER 7: TESTING
7.6

Ground Current Accuracy

7.6.1

50:0.025 Ground Accuracy Test

239 MOTOR PROTECTION RELAY – INSTRUCTION MANUAL
Courtesy of NationalSwitchgear.com
1. Alter the following setpoints:
S2: SYSTEM SETUP\CT INPUTS\GROUND SENSING:
S2: SYSTEM SETUP\CT INPUTS\GROUND CT PRIMARY:
S4: PROTECTION\GROUND CURRENT\GROUND TRIP:
S4: PROTECTION\GROUND CURRENT\GROUND ALARM:
2. To determine if the relay is reading the proper ground current, inject various ground
currents shown in the table below into the 5A ground input and view the readings in
A2: METERING\CURRENT\GROUND CURRENT
stated in the table.
Table 7–4: Ground Current Accuracy Test
INJECTED EXPECTED GROUND
CURRENT CURRENT READING †
0.5
1.0
3.5
5.0
6.0
† displayed current
=
1. Alter the following setpoint:
S2: SYSTEM SETUP\CT INPUTS\GROUND SENSING:
2. Inject the values shown below as primary values into a GE Multilin 50:0.025 Core
Balance CT. View the readings in
verify with the expected readings shown in the following table.
Table 7–5: 50:0.025 Ground Current Accuracy Test
INJECTED EXPECTED GROUND
PRIMARY CURRENT READING
CURRENT
0.25 A
1 A
10 A
25 A
and verify with the expected readings
ACTUAL GROUND CURRENT
10
20
70
100
120
PHASE CT PRIMARY
⎛
× ----------------------------------------------- -
injected current
⎝
5 A
A2: METERING\CURRENT\GROUND CURRENT
ACTUAL GROUND CURRENT
0.25 A
1.00 A
10.00 A
25.00 A
X:5
100
OFF
OFF
READING
⎞
⎠
CORE BAL 50:0.025
and
READING
7–101