7SG11 Argus Technical Reference
©2013 Siemens Protection Devices Limited
P20007 Page 35 of 71
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.
Vbc
Ia
Vca
2-out-of-3
logic
(fwd)
Dir'n Blk A REV
Dir'n Blk B REV
Dir'n Blk C REV
P300008 Protection Functions / Dir'n P/F
Vab
Ic
Ib
fwd
rev
fwd
rev
fwd
rev
2-out-of-3
logic
(rev)
Dir'n Blk A FWD
Dir'n Blk B FWD
Dir'n Blk C FWD
Event
Event
Event
Event
Event
Event
Phase A forward
Phase B forward
Phase C forward
Phase A reverse
Phase B reverse
Phase C reverse
P/F Charact Angle
2-Out-Of-3 Logic
Figure 2.7-1
Functional Diagram – Phase-fault Directional Element
Vn
Ie
Dir'n Blk E/F REV
P300008 Protection Functions / Dir'n E/F
fwd
rev
Dir'n Blk E/F FWD
Event
Event
Earth forward
Earth reverse
E/F Charact Angle
Figure 2.7-2
Functional Diagram – Earth-fault Directional Element
Table 2-17
Directional Settings
Sub-menu:
Directional
Setting name
Range (
bold
= default)
Units Notes
