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7SR11 & 7SR12 Commissioning and Maintenance Guide
CB Open
CB Closed
CB
&
Open
CB
&
Closed
Reduced
Reduced
Current Level
Current
c
Enabled
Disabled
<
IL1
<
IL2
<
IL3
Ensure that the Cold load active is not raised. This can be reset by CB closed for more than the Cold Load Drop-
off Time or current less than the Reduced Current Level for greater than the Reduced Current Time. Check the
Cold Load Pick-up Delay by applying or simulating CB Open. Measure the time delay before Cold Load Active is
raised. Apply current above the Reduced Current Level if this functionality is Enabled before applying CB Closed.
Measure the time for Cold Load Active to reset.
2.4.1
Inverse Time Overcurrent (51C)
It will be advantageous to map the function being tested to temporarily drive the relevant Pickup output in the
Pickup Config sub-menu in the Output Config menu as this will allow the Pick-up led to operate for the function.
Gradually increase current until Pickup LED operates.
Apply 2x setting current and record operating time,
Apply 5x setting current and record operating time.
Compare to calculated values for operating times
Ph.
Dir
P.U.
I
(I
)
L1
A
D.O.
I
(I
)
&
L2
B
TIMING
I
(I
)
L3
C
TESTS
©2017 Siemens Protection Devices Limited
Cold Load
Enabled
Disabled
Inhibit Cold Load
Pick-up Time
Drop-off Time
Reduced Current DTL
&
Figure 2-5
Char.
Is
TM
(NI EI VI LTI,
(A)
DTL)
&
S
Q
1
51c-n Setting
R
51c-n Charact
51c-n Time Mult
51c-n Delay (DTL)
51c-n Min. Operate Time
51c-n Follower DTL
51c-n Reset
c
c
L1 Dir En
c
L2 Dir En
c
L3 Dir En
Cold Load Logic diagram
Operate Current
P.U.
D.O.
Tol
(Amps)
(Amps)
51c
See Delayed
Overcurrent
(51-n)
Pickup
1
General Pickup
trip
Pickup
trip
Pickup
1
51-n
trip
Operate Time
2 x Is
5 x Is
Tol
(sec)
(sec)
Chapter 6 Page 20 of 72
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