TLF/DAT Earth Fault Tests - Secondary Current Injection
Follow the below steps to perform the TLF/DAT earth fault test - secondary current injection:
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Select the required CT ratio using 12 pin connectors on the PCBA board.
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Replace both the fuses with temporary shorting links on PCBA board.
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Connect the secondary injection test equipment as shown in below Figure – Schematic Diagram of TLF/DAT Earth Fault Tests - Secondary Current Injection.
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Close the disconnector and circuit breaker (respective ring switch mechanism) to Main ON.
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Select the earth fault sensitivity using the 2 pin connector as shown in Figure – Earth Fault Sensitivity.
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Inject the CT secondary current 5 A in each phase in turn using the CT terminal block available in LV panel, accordance with the below Table – Range Phase Under Test, to help ensuring the correct actions result and the tripping levels are within the tolerance.
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Repeat steps 1 to 6 for remaining parts of phases (and CT ratio if required).
Range Phase Under Test
|
Range phase under test |
CT ratio |
Trip level (Earth fault setting) |
Circuit breaker action |
||
|---|---|---|---|---|---|
|
Low earth fault setting |
High earth fault setting |
No earth fault |
|||
|
L1 |
50/5 A |
1.8–3.0 A |
2.5–4.0 A |
No Trip |
Trip |
|
L2 |
Trip |
||||
|
L3 |
Trip |
||||
|
L1 |
100/5 A |
1.4–2.25 A |
2.25–3.0 A |
No Trip |
Trip |
|
L2 |
Trip |
||||
|
L3 |
Trip |
||||
|
L1 |
200/5 A |
1.25–1.875 A |
2.125–3.0 A |
No Trip |
Trip |
|
L2 |
Trip |
||||
|
L3 |
Trip |
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