Time Delayed Derived Earth Fault Protection (51N); Figure 3-4 Logic Diagram: Time Delayed Derived Earth Fault Protection - Siemens 7SR45 Argus User Manual

3.4

Time Delayed Derived Earth Fault Protection (51N)

One time delayed derived earth fault element is provided in the 7SR45 Argus Relay.
51N-1
51N-n Setting sets the pick-up current level.
A total of 7 shaped characteristics are provided from IEC and ANSI. An inverse definite minimum time (IDMT)
characteristic is selected 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 (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 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 the 51N-n MinOperate setting.
A fixed additional operate time can be added to the characteristic using the 51N-n Follower setting.
Operation of the time delayed derived earth fault elements can be inhibited by assigning binary inputs.
Inhibit 51N-n
Gn 51N - n Element
Disabled
Enabled
Inhibit 51N-n
IL1
IL2
IL 3
Figure 3-4
The following are the 51N-n supported curve characteristic:
• DTL, IEC-NI, IEC-VI, IEC-EI, IEC-LTI, ANSI-MI, ANSI-VI, ANSI-EI
Operating time for IEC : t
Operating time for IEEE/ANSI : t
Reset time for IEC/IEEE/ANSI :
©2018 Siemens Protection Devices Limited
A binary input.
&
Gn 51N - n Setting
Gn 51N - n Char
Gn 51N - n Time Mult
Gn 51N - n Delay (DTL)
Gn
51N - n MinOperate
Gn
51N- n Follower
Gn
51N - n Reset
c
I
N
∑
Logic Diagram: Time Delayed Derived Earth Fault Protection
K
α
=
I
X Tm
op
( )
1
Is
A
+ B
P
=
I
op
( )
1
Is
R
n
t =
X Tm
I
r
( )
1
Is
Chapter 1 - 7SR45 Description of Operation
'
Pickup
trip
X Tm
General Pickup
51N- n
Chapter 1 Page 28 of 48