IEC Reset
If the element is configured as an IEC characteristic, it may have an IEC (decaying) reset delay applied.
IEC reset times from operated condition to fully reset are as follows for zero applied current and Time multi-
plier (Tm) = 1.0. The reset curve characteristic type and Tm is defined by the operating characteristic.
Curve Fully Operated to Reset with Zero Current Applied
& Tm = 1 (s)
IEC-NI 9.7
IEC-VI 43.2
IEC-EI 58.2
IEC-LTI 80
Apply current in the following sequence, a) 2 times setting for a time to ensure element operation, b) Zero
current for the reset time above (xTm), c) 2 times setting for a time to ensure element operation. Check that
the second operation (c) is similar to the first (a) and in line with the expected operate time for the element at
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)
Element Blocking
The 51CL overcurrent elements can be blocked by Binary Input Inhibit. This functionality should be
checked.
Element
BI Inhibits
51CL
51V Voltage Dependent Overcurrent – Phase
OC Phase
Control Voltage
CT1(I
A
) V
12
(V
AB
)
CT2(I
B
) V
23
(V
BC
)
CT3(I
C
) V
31
(V
CA
)
IDMT Phase Overcurrent elements 51-n should be tested for pick-up and timing before this function is
tested. The General Pickup LED can be used to assess operation of this function if other functions are disa-
bled or if the setting allocating General Pickup is temporarily modified.
Apply nominal 3 phase balanced voltage. Apply 3 phase balanced current at a level below the normal 51-n
setting but above the effective 51V-n setting. Ensure that the thermal rating of the relay is not exceeded.
Gradually reduce the voltage until the a-b voltage is less than the Voltage setting. Pickup LED operation
can be used to confirm the Voltage setting. If the 51V-n current setting is above the continuous rating of the
relay an alternative procedure should be used, apply test current in short duration shots with applied voltage
being gradually reduced for each subsequent shot.
Apply nominal 3 phase balanced voltage. Increase the voltage such that the a-b voltage is 110 % of the
Voltage setting. Test current can be applied as 3 phase balanced current or as a single phase a-b current via
CT1 and returning through CT2. Gradually increase the a-b phase current or balanced 3P current until Pickup
LED operates. Confirm result of phase O/C test above.
Reduce the applied voltage to a level such that VAB phase-phase voltage is less than 90 % of the setting. The
element threshold is operated by phase to phase voltage but the most common connection of the 3 phase
voltage inputs is phase to neutral.
Gradually increase the CT1 phase-phase current until Pickup LED operates.
9.9.18
Functional Tests
9.9 Protection Functional Tests
Reyrolle 7SR5, Overcurrent Protection Device, Device Manual 487
C53000-G7040-C014-1, Edition 11.2019
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