7SR10 Description of Operation
©2018 Siemens Protection Devices Limited Chapter 1 Page 36 of 77
3.3.3 Time Delayed Measured Earth Fault Protection (51G)
Two instantaneous measured earth fault elements are provided in the 7SR1002/7SR1003 relay and four elements
are provided in the 7SR1004 relay.
51G-1, 51G-2, (51G-3 & 51G-4 – 7SR1004)
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.
Operating curve characteristics are illustrated in
Section 3 – ‘Performance Specification’
.
The
51G-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
A binary or virtual input.
79 E/F Inst Trips:
51G-n
When ‘delayed’ trips only are allowed in the auto-reclose sequence
(
79 E/F Prot’n Trip n
=
Delayed
).
51G-n Inrush Action: Block
Operation of the inrush current detector function.
51G-n VTSAction:
Inhibit
Operation of the VT Supervision function.
General Pickup
51G-n
If directional elements are not present this block is
omitted and the '51G-n Dir En' signal is set TRUE.
Forward
Reverse
51G-n Dir
Non-Dir
≥
1
&
&
51G-n Dir En
67G Fwd
67G Rev
51G-n VTS Action
Off
Non Dir
Inhibit
VT Fail
&
&
&
≥
1
IL
4
(I
G
)
51G/50G Measurement
51G-n Setting
51G-n Charact
51G-n Time Mult
51G-n Min Operate Time
51G-n Reset
51G-n Delay (DTL)
51G-n Follower DTL
c
Pickup
trip
Inhibit 51G-n
&
51G-n Element
Enabled
Disabled
81HBL2
51G-n Inrush
Action
Off
Inhibit
&
51G-n Dir En
&
79 P/F Inst Trips
= 51G-n
79 P/F Prot’n Trip n
= Delayed
AUTORECLOSE
Figure 3-10 Logic Diagram: Measured Time Delayed Earth Fault Element (51G)
Summary of Contents for 7SR10 Argus Series
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