Chapter 1 - 7SR45 Description of Operation
©2018 Siemens Protection Devices Limited Chapter 1 Page 25 of 48
3.2 Time Delayed Overcurrent Protection (51)
One time delayed overcurrent element is provided in the 7SR45 Argus Relay.
51-1
51-n Setting
sets the pick-up current level.
A total of 7 shaped characteristics are provided from IEC and ANSI standards. An inverse definite minimum time
(IDMT) characteristic is selected using
51-n Char
. A time multiplier is applied to the characteristic curves using
the
51-n Time Mult
setting. Alternatively, a Definite Time Lag (DTL) can be chosen using
51-n Char
. When
Definite Time Lag (DTL) is selected the time multiplier is not applied and the
51-n Delay (DTL)
setting is used
instead.
The
51-n Reset
setting can apply a
definite time delayed reset
or when the operation is configured as an IEC or
ANSI and if the reset is selected as
(IEC/ANSI) DECAY
reset, the associated reset curve will be used.
A minimum operate time for the characteristic can be set using
51-n MinOperate
setting.
A fixed additional operate time can be added to the characteristic using
51-n Follower
setting.
Operation of the time delayed overcurrent elements can be inhibited by assigning binary inputs.
Inhibit 51-n
A binary input.
≥
1
General Pickup
51-n
Gn 51-n Setting
Gn 51-n Char
Gn 51-n Time Mult
Gn 51-n Delay (DTL)
Gn 51-n Reset
c
Gn 51-n Follower
Gn 51-n MinOperate
IL1
IL2
IL3
Gn 50/51
Measurement
c
Pickup
trip
c
Pickup
trip
c
Pickup
trip
Inhibit 51-n
Gn 51-n Element
Enabled
Disabled
&
≥
1
Figure 3-2
Logic Diagram: Time Delayed Overcurrent Element