7SR10 Description of Operation
©2018 Siemens Protection Devices Limited Chapter 1 Page 32 of 77
3.2.3 Time Delayed Derived Earth Fault Protection (51N)
Two time delayed derived earth fault elements are provided in the 7SR1002/7SR1003 relay and four elements are
provided in the 7SR1004 relay.
51N-1, 51N-2, (51N-3 & 51N-4 – 7SR1004)
51N-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
51N-n Char
. A time multiplier is applied to the characteristic curves
using the
51N-n Time Mult
setting. Alternatively, a definite time lag delay (DTL) can be chosen using
51N-n
Char
. When definite time lag (DTL) is selected the time multiplier is not applied and the
51N-n Delay (DTL)
setting is used instead.
The
51N-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 the
51N-n Min. Operate Time
setting.
A fixed additional operate time can be added to the characteristic using the
51N-n Follower DTL
setting.
Where directional elements are present the direction of operation can be set using
51N-n Dir. Control
setting.
Directional logic is provided independently for each 51N-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 51N-n
A binary or virtual input.
79 E/F Inst Trips:
51N-n
When ‘delayed’ trips only are allowed in the auto-reclose sequence
(
79 E/F Prot’n Trip n
=
Delayed
).
51N-n Inrush Action: Block
Operation of the inrush current detector function.
51N-n VTSAction:
Inhibit
Operation of the VT Supervision function.
Summary of Contents for 7SR10 Argus Series
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