Time Delayed Measured Earth Fault Protection (51G); Figure 3-10 Logic Diagram: Measured Time Delayed Earth Fault Element (51G) - Siemens 7SR12 Argus Manual

3.3.3 T D
IME ELAYED
Two instantaneous derived earth fault elements are provided in the 7SR11 relay and four elements are provided
in the 7SR12 relay.
51G-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 51G-n Char. A time multiplier is applied to the characteristic curves
using the 51G-n Time Mult setting. Alternatively, a definite time lag (DTL) can be chosen using 51G-n Char.
When DTL is selected the time multiplier is not applied and the 51G-n Delay (DTL) setting is used instead. The
full list of operating curves is given in Section 2 – 'Settings, Configuration and Instruments Guide'. Operating
curve characteristics are illustrated in Section 3 – 'Performance Specification'.
The 51-n Reset setting can apply a definite time delayed reset, or when the operation is configured as an IEC or
ANSI or user characteristic if the reset is selected as IEC/ANSI (DECAYING) reset the associated reset curve will
be used. 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 51G-n Min. Operate Time setting.
A fixed additional operate time can be added to the characteristic using 51G-n Follower DTL setting.
Where directional elements are present the direction of operation can be set using 51G-n Dir. Control setting.
Directional logic is provided independently for each 51G-n element e.g. giving the option of using two elements
set to forward and two to reverse.
Operation of the time delayed measured earth fault elements can be inhibited from:
Inhibit 51G-n
79 E/F Inst Trips: 51G-n
(79 E/F Prot'n Trip n = Delayed).
50-n Inrush Action: Block
51G-n VTSAction: Inhibit
51G-n Inrush
Action
Off
Inhibit
81HBL2
AUTORECLOSE
79 P/F Inst Trips
= 51G-n
79 P/F Prot'n Trip n
= Delayed
51G-n Dir
Non-Dir
Forward
Reverse
67G Fwd
67G Rev

Figure 3-10 Logic Diagram: Measured Time Delayed Earth Fault Element (51G)

©2017 Siemens Protection Devices Limited
M E
EASURED ARTH
51G-1, 51G-2, (51G-3 & 51G-4 – 7SR12)
A binary or virtual input.
When 'delayed' trips only are allowed in the auto-reclose sequence
Operation of the inrush current detector function.
Operation of the VT Supervision function (7SR1205 & 7SR1206).
51G-n Element
Disabled
Enabled
Inhibit 51G-n
&
51G-n Dir En
&
51G/50G Measurement
I (I )
4 G
&
&
7SR11 & 7SR12 Description Of Operation
F P
AULT ROTECTION
&
51G-n Setting
51G-n Charact
51G-n Time Mult
51G-n Delay (DTL)
51G-n Min Operate Time
51G-n Follower DTL
51G-n Reset
c
Pickup
trip
If directional elements are not present this block is
51G-n VTS Action
omitted and the '50G-n Dir En' signal is set TRUE.
Off
Non Dir
Inhibit
& &
VT Fail
≥1
&
(51G)
General Pickup
51G-n
≥1
51G-n Dir En
Chapter 1 Page 41 of 88