Two-Out-Of-Three Gate; Voltage Memory - Siemens 7SG11 Manual

In relays with type I directional elements the residual voltage is obtained from the open delta connection of the
tertiary windings of the line-N voltage transformers. The earth-fault characteristic angles can be user programmed
to 0 , -15 , -45 or -65 using the Protection:E/F Charact Angle setting.
In relays with type II directional elements an open delta tertiary winding can be used or alternatively the relay will
itself calculate the residual voltage internally from the three applied phase-earth voltages. With these relays any
characteristic angle between -90 and +90 can be selected. The characteristic angle setting should be matched
to the expected nominal angle of system fault.
Note that when type I directional Argus relays are used on 60Hz systems the nominal characteristic angles will
change slightly, typically P/F by less than +5 and E/F by less than -5 .
2.7.2

Two-out-of-three Gate

This feature is applicable to relays with three directional phase-fault poles. It provides the means of achieving
absolute discrimination, between two directional overcurrent protection relays, in power system applications
where +1 : -2 : +1 fault current distribution can occur.
When the Directional:2-Out-Of-3 Gate Logic setting is set to ON, the directional elements will only operate for the
majority direction, e.g. if phase A and C detect forward current flow and phase B detects reverse current flow,
phase A and C will operate forwards, while phase B will be inhibited.
2.7.3

Voltage Memory

In the condition of a 3 phase fault where the polarising voltage collapses the relay can maintain the Forward or
Reverse direction for each pole for up to 0.5 s. The Directional:Voltage Memory setting is used to set the amount of
time the relay will hold the memory of the direction.
P/F Charact Angle
Vbc
Ia
Vca
Ib
Vab
Ic
Figure 2.7-1
E/F Charact Angle
Vn
Ie
Figure 2.7-2
Table 2-17 Directional Settings
Sub-menu: Directional
Setting name
©2013 Siemens Protection Devices Limited
Phase A forward
fwd
Phase B forward
rev
Phase C forward
fwd
rev
Phase A reverse
fwd
Phase B reverse
rev
Phase C reverse
Functional Diagram – Phase-fault Directional Element
Earth forward
Event
fwd
Earth reverse
Event
rev
Functional Diagram – Earth-fault Directional Element
Range (bold = default)
7SG11 Argus Technical Reference
2-Out-Of-3 Logic
Event
2-out-of-3
logic
Event
(fwd)
Event
Event
2-out-of-3
logic
Event
(rev)
Event
Units Notes
Dir'n Blk A FWD
Dir'n Blk B FWD
Dir'n Blk C FWD
Dir'n Blk A REV
Dir'n Blk B REV
Dir'n Blk C REV
P300008 Protection Functions / Dir'n P/F
Dir'n Blk E/F FWD
Dir'n Blk E/F REV
P300008 Protection Functions / Dir'n E/F
P20007 Page 35 of 71