Inverse Time Overcurrent (51Sef) - Siemens 7SR12 Argus Manual

During testing of the 67SEF Ires select residual current setting it is essential that the wattmetric power
setting is also exceeded. This can usually be achieved by applying the test current to the SEF input
whilst applying a nominal single phase voltage, in anti-phase with the current, to all 3 phase to neutral
voltage inputs. In this way, the wattmetric power is equal to the product of 3 times the applied voltage
and the applied current and this should always be greater than the Wattmetric power setting.
2.9.4

Inverse Time Overcurrent (51SEF)

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
P.U. Ph. Dir
D.O.
&
TIMING
I
4
TESTS
Calculated Timing values in seconds for TM =1.0
Curve
IEC-NI
IEC-VI
IEC-EI
IEC-LTI
ANSI-MI
ANSI-VI
ANSI-EI
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.
If VTS action is set to BLOCK, this option should be tested. Apply balanced voltage and current. Reduce a-phase
voltage to cause a VTS condition. Increase a-phase current and check that the element does not operate.
If VTS action is set to Non-Directional, this option should be tested. Apply balanced voltage and current. Reduce
a-phase voltage to cause a VTS condition. Increase a-phase current and check that the element operates at its
normal setting. Reverse the voltage phase direction whilst checking that the element does not reset.
2.9.4.1 Element Blocking
The Sensitive Earth Fault elements can be blocked by Binary Input Inhibit, VT Supervision and Wattmetric
protection. The Characteristic can be made non-directional by VT Supervision. This functionality should be
checked.
Element
51SEF-1
51SEF-2
51SEF-3
51SEF-4
50SEF-1
50SEF-2
©2017 Siemens Protection Devices Limited
Char. Is TM
(NI EI VI LTI, (A)
DTL)
2 xIs
10.03
13.50
26.67
120.00
3.80
7.03
9.52
7SR11 & 7SR12 Commissioning and Maintenance Guide
Operate Current
P.U. D.O. Tol
(Amps) (Amps)
BI Inhibits
Operate Time
2 x Is 5 x Is Tol
(sec) (sec)
5 xIs
4.28
3.38
3.33
30.00
1.69
1.31
1.30
VTS action
Chapter 6 Page 35 of 72