this current level. Repeat the test with the reset time (b) reduced to 50 % of the previous value. Ensure that
the second operate time (c) is 50 % of the first (a) operate time.
Operate Time
(expected)
Reset Time
(calculated)
Operate Time
(measured)
50 % Reset Time
(calculated)
50 % Operate
Time (calcu-
lated)
50 % Operate
Time (meas-
ured)
First test (c) Second Test (c)
51CL Cold Load Overcurrent – Phase
The CB must be open for more than the Cold Load Pick-up Time to allow testing of this function. It may
be convenient to reduce this setting to suit the test procedure. If the CB is open throughout the tests, the
Cold Load protection settings can be tested provided that the current is not allowed to fall below the level
of the Reduced Current Level for more than the Reduced Current Time during testing. It may be
convenient to set the Reduced Current setting to Disabled for the duration of the test. The Cold Load
Active output is provided and can be used as an indication during testing.
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.
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 Pickup LED to operate for
the function.
Gradually increase current until Pickup LED operates.
Apply 2 times setting current and record operating time.
Apply 5 times setting current and record operating time.
Compare to calculated values for operating times.
Table 9-7
P.U. D.O. & Timing Tests
Ph. Dir Char.
(NI EI VI
LTI,
DTL)
I
set
(A) Tm Operate Current Operate Time
P.U.
(Amps)
D.O.
(Amps)
Tol 2 ⋅ I
set
(sec)
5 ⋅ I
set
(sec)
Tol
CT1(I
A
)
CT2(I
B
)
CT3(I
C
)
Calculated timing values in seconds for Tm = 1.0
Curve
2 ⋅ I
set
5 ⋅ I
set
IEC-NI 10.03 4.28
IEC-VI 13.5 3.38
IEC-EI 26.67 3.33
IEC-LTI 120 30
ANSI-MI 3.8 1.69
ANSI-VI 7.03 1.31
ANSI-EI 9.52 1.3
Note that the operate time may be subject to the Minimum Op Time setting for the element and/or may
have a Follower DTL applied.
9.10.14
Functional Tests
9.10 Protection Functional Tests
438 Reyrolle 7SR5, Transformer Protection Device, Device Manual
C53000-G7040-C015-1, Edition 11.2019
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