Time Delayed Measured Earth Fault Protection (51G); Figure 3-6 Logic Diagram: Time Delayed Measured Earth Fault Element - Siemens 7SR45 Argus User Manual

3.6

Time Delayed Measured Earth Fault Protection (51G)

One time delayed measured earth fault element is provided in the 7SR45 Argus Relay.
51G-1
51G-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 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 51G-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. The reset
mode is significant where the characteristic has reset before issuing a trip output.
A minimum operate time for the characteristic can be set using 51G-n MinOperate setting.
A fixed additional operate time can be added to the characteristic using 51G-n Follower setting.
Operation of the time delayed measured earth fault elements can be inhibited by assigning binary inputs.
Inhibit 51G-n
Gn 51G- n Element
Disabled
Enabled
Inhibit 51G-n
Gn 51G
/50G Measurement
I
G
Figure 3-6
The following are the 51G-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
51G- n Setting
Gn
51G-n Char
Gn
51G- n Time Mult
Gn 51G-n Delay ( DTL )
Gn 51G- n MinOperate
Gn
51G- n Foll ' ower
Gn
51G- n Reset
c
Logic Diagram: Time Delayed Measured Earth Fault Element
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
General Pickup
Pickup
51 G - n
trip
X Tm
Chapter 1 Page 31 of 48