Time Delayed Sensitive Earth Fault Protection (51Sef); Figure 3-14 Logic Diagram: 7Sr11 Sef Time Delayed Element (51Sef) - Siemens 7SR12 Argus Manual

3.4.3 T D
IME ELAYED
Two sensitive earth fault elements are provided in the 7SR11 relay and four elements are provided in the 7SR12
relay.
51SEF-n Setting sets the pick-up current level.
A number of shaped characteristics are provided. An inverse definite minimum time (IDMT) characteristic is
selected from IEC and ANSI curves using 51SEF-n Char. A time multiplier is applied to the characteristic curves
using the 51SEF-n Time Mult setting. Alternatively, a definite time lag (DTL) can be chosen using 51SEF-n Char.
When DTL is selected the time multiplier is not applied and the 51SEF-n Delay (DTL) setting is used instead.
The 51SEF-n Reset setting can apply a definite time delayed reset, or when configured as an IEC or ANSI
characteristic an IEC/ANSI (DECAYING) reset. The reset mode is significant where the characteristic has reset
before issuing a trip output – see 'Applications Guide'.
A minimum operate time for the characteristic can be set using 51SEF-n Min. Operate Time setting.
A fixed additional operate time can be added to the characteristic using 51SEF-n Follower DTL setting.
Where directional elements are present the direction of operation can be set using 51SEF-n Dir. Control setting.
Directional logic is provided independently for each 51SEF-n element e.g. giving the option of using two elements
set to forward and two to reverse.
Operation of the time delayed earth fault elements can be inhibited from:
Inhibit 51SEF-n
79 SEF Inst Trips: 51SEF-n
51SEF-n VTSAction: Inhibit
Directional elements will not operate unless the zero sequence voltage (V
Voltage setting i.e. the residual voltage is greater than 3 times this setting and the phase is in the
Forward/Reverse operating range. If 67SEF Wattmetric is set to Enabled, the calculated residual real power
must be above the 67SEF Wattmetric Power setting. The residual power P
component of 3V I and therefore the wattmetric component of 9V
0 SEF
AUTORECLOSE
79 P/F Inst Trips
= 51SEF-n &
79 P/F Prot'n Trip n
= Delayed

Figure 3-14 Logic Diagram: 7SR11 SEF Time Delayed Element (51SEF)

©2017 Siemens Protection Devices Limited
S E
ENSITIVE ARTH
51SEF-1, 51SEF-2, (51SEF-3 & 51SEF-4– 7SR12)
A binary or virtual input
When 'delayed' trips only are allowed in the auto-reclose sequence
(79 SEF Prot'n Trip n = Delayed).
Operation of the VT Supervision function (7SR1205 & 7SR1206).
51SEF-n Element
Disabled
Enabled
Inhibit 51SEF-n &
I
4
7SR11 & 7SR12 Description Of Operation
F P (51SEF)
AULT ROTECTION
0
I
0 0
51SEF-n Setting
51SEF-n Charact
51SEF-n Time Mult
51SEF-n Delay (DTL)
51SEF-n Min Operate Time
51SEF-n Follower DTL
51SEF-n Reset
c
Pickup
trip
(I )
SEF
) is above the 67SEF Minimum
is equal to the wattmetric
res
General Pickup
51SEF-n
Chapter 1 Page 45 of 88