TLF/DAT Earth Fault Tests - Primary Current Injection
Follow the below steps to perform the TLF/DAT earth fault test - primary current injection:
-
Select the required CT ratio using 12 pin connectors on the PCBA board.
-
Replace both the fuses with temporary shorting links on PCBA board.
-
Connect 3-phase shorting link (200 A rated) at L1, L2, and L3 connections of bushing.
-
Connect the primary injection test equipment as shown in below Figure – Schematic Diagram of TLF/DAT Earth Fault Tests - Primary Current Injection.
-
Close the disconnector and circuit breaker (respective ring switch mechanism) to Main ON.
-
Select the earth fault sensitivity using the 2 pin connector as shown in Figure – Earth Fault Sensitivity.
-
Inject a primary current instantaneously (pulse) in accordance with the below Table – Range Phase Under Test, to help ensuring the correct actions result and the tripping levels are within the tolerance.
-
Repeat steps 1 to 7 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 |
18–30 A |
25–40 A |
No Trip |
Trip |
|
L2 |
Trip |
||||
|
L3 |
Trip |
||||
|
L1 |
100/5 A |
28–45 A |
45–60 A |
No Trip |
Trip |
|
L2 |
Trip |
||||
|
L3 |
Trip |
||||
|
L1 |
200/5 A |
50–75 A |
85–120 A |
No Trip |
Trip |
|
L2 |
Trip |
||||
|
L3 |
Trip |
||||