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Time delayed residual overcurrent protection
(TEF)
Table 23:
Operate time formulas
Characteristics
Operate time (s)
Normal inverse
t
Very inverse
t
Extremely inverse
t
Logarithmic inverse
t
Where:
I
is a multiple of set current 3I
k
is a time multiplying factor, settable in the range of 0.05 to 1.10
Also check the tMin (minimum operate time) and IMin (minimum oper-
ate current) functions.
10. Activate the TEF--BC input to check the function of the switch-on-
to-fault logic.
11. Check that the TEF--TRSOTF output is activated with a 300 ms time
delay when injecting a current two times the set IMin operate value
in forward direction.
12. Set the phase angle of the polarising voltage to ϕ =245° and check
that the directional current function and the switch-onto-fault logic
gives no operation when the current is in the reverse direction.
13. Connect the rated DC voltage to the TEF--BLOCK configured binary
input and switch on the fault current.
No TEF--TRIP nor TEF--START signal should appear.
14. Switch off the fault current.
15. Connect the rated DC voltage to the TEF--BLKTR configured binary
input and switch on the fault current.
No TEF--TRIP nor TEF--TRSOTF should appear. But the output
TEF--START shall be activated.
16. Continue to test another function or complete the test by setting the
test mode to off.
0.14
------------------- - k ⋅
=
0.02
I
–
1
13.5
---- ------- k ⋅
=
I 1
–
80
------------- k ⋅
=
2
I
1
–
(
⋅
)
5.8
1.35
ln
I
=
–
>
0
Chapter 13
Verifying settings by secondary
injection
(Equation 1)
(Equation 2)
(Equation 3)
(Equation 4)
119
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