TERASAKI AME Series, Instruction Manual

Page: 30 / 40

KRB-5200h
-24-
Calculation Example:
CT RATED CUR. I
CT
: 250 / 0.05 A
RATED CUR. In: 231 A
LONG TIME I
1
: 1.15 X In
T
1
: 20 SEC at 1.2 X I
1
Assuming the conditions shown above, the test current is given by
(A)
④
Close the ACB.
⑤
Check for the long time-delay trip pick-up current (I
1
).
To do this, increase the test current gradually and
measure the current at which the I
1
pick-up LED begins
to flicker.
It is acceptable when the measured current falls within
the range of 92.5 to 107.5% of I
1
(or 92.5 to 117.5% of
I
1
when I
1
is 50% or less of I
CT
).
After testing, decrease the test current. Otherwise,
the ACB will trip open.
⑥
Check the time delay setting (T
1
).
Caution : When the ACB trips open, turn off the power immediately.
Caution : An error of 1% in test current will lead to an error of 4% in time delay. Apply the
accurate test current to the OCR.
To check the time delay setting, apply the test current obtained at step
③
and, using a
stopwatch, measure the time from current application to ACB tripping.
It is acceptable when the measured time falls within the range of 85 to 115% of T
1
(or 80 to
120% of T
1
when I
1
is 50% or less of I
CT
).
⑦
Repeat steps
⑤
and
⑥
for remaining phases.
⑧
After completion of the tests, return the ACB to the original state.

If the tests show any problem, contact our branch office or your local agency.
Caution : When checking the short time-delay trip characteristics
1) Apply the test current for 150 ms as a guideline.
2) Set the test current to I
2
x 1.6 as a guideline. Never increase the test current to the
instantaneous trip pick-up current (I
3
) or more.
3) Applying the test current close to the short time-delay trip pick-up current (I
2
) may somewhat
lengthen the operating time. See the operation characteristic curves on page 26.
4) Test procedures:
Close the ACB.
Apply the test current of not more than 85% of I
2
and check if the ACB dose not trip.
Then apply the test current of 120 to 160% of I
2
and check if the ACB trips open within approx.
150 ms.
231
0 05
250
115 1 2 0 0638
   
.
. . .
I
１
Pick-up LED