Aided Def Blocking Scheme; Figure 84: Aided Def Por Scheme - GE MiCOM P40 Technical Manual

P446sv
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P446SV
A
CB Open
DEF-Reverse
LD0V
DEF-Forward
DEF Inst
DEF Bu1
DEF Bu2
DEF IDMT
E03518

Figure 84: Aided DEF POR scheme

5.6

AIDED DEF BLOCKING SCHEME

The scheme has the same features/requirements as the corresponding Distance scheme and provides sensitive
protection for high resistance earth faults.
The signalling channel is keyed from operation of the reverse Aided DEF element (DEF REV Set). If the remote
device's forward Aided DEF element (DEF FWD Set) has picked up, it operates after the Aid. 1 DEF Dly. expires if no
block is received.
Where 't' is shown in the diagram this signifies the time delay associated with an element. To allow time for a
blocking signal to arrive, a short time delay on aided tripping must be used.
The logic is:
Send logic: Key channel if DEF REV Set picks up
Trip logic: Trip if DEF FWD Set AND Channel NOT Received, after Aid. 1 DEF Dly. expires.
P446SV-TM-EN-1
&
CRx
&
CTx
1
&
&
1
t
Bu1
t
Bu2
t
IDMT
Selectable features
DEF Forward
ZL
DEF Forward
CRx
CTx
1
Trip
Trip
A
B
1
Chapter 8 - Carrier Aided Schemes
B
&
CB Open
&
DEF-Reverse
LD0V
&
&
DEF-Forward
DEF Inst
DEF Bu1
t
Bu1
DEF Bu2
t
Bu2
DEF IDMT
t
IDMT
189

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