E03501
Zone 3
Zone 2
Zone 1
Zone 1
Zone 2
Zone 3
Trip A Trip B
Z4
Z3
Z2
Zp
Z1
Z4
Z3
Z2
Zp
Z1
TZ4
TZ3
TZ2
TZp
TZ1
TZ4
TZ3
TZ2
TZp
TZ1
Optional features of scheme
&
&
1
1
CRx
CRx
CTx
CTx
Z
Z
A
B
Figure 71: Aided Distance PUR scheme
4.2
PERMISSIVE OVER-REACH SCHEME
Permissive Over-reach schemes are variously referred to as POR, POP, POTT. We normally use the term POR.
In a Permissive Overreach scheme the channel is keyed (that means that the aiding signal is asserted) by the
pickup of an over-reaching Zone 2 element.
To use this scheme, you need to set the relevant setting (Aid. 1 Selection or Aid. 2 Selection) in the SCHEME LOGIC
column to POR.
If a remote protection element detects a forward fault and receives a POR signal, the protection operates without
further delay. Faults in the last 20% of the protected line are therefore cleared with minimal time delay.
Note:
This assumes a 20% typical end-zone when Zone 1 is set to 80% of the protected line.
Chapter 8 - Carrier Aided Schemes P446SV
172 P446SV-TM-EN-1
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