6 AIDED DELTA SCHEME LOGIC
If either a Permissive Overreaching scheme or a Blocking schemes is selected, it can be used to implement
Directional Comparison(Aided Delta) protection.
Caution:
Aided Delta should not be used on a communications channel if that channel is being used to
implement an Aided Distance Scheme or an Aided DEF scheme. You should ensure that the Aided
Distance and Aided DEF elements are disabled if you want to apply the Aided Delta (Directional
Comparison Protection).
6.1
AIDED DELTA POR SCHEME
The channel for an Aided Delta POR scheme is keyed by operation of the overreaching Delta Forward elements. If
the remote device has also detected a forward fault upon receipt of this signal, the protection operates.
If the signalling channel fails, Basic distance scheme tripping is available.
The logic is:
● Send logic: Key channel if a Detla Fault Forward is detected
● Permissive trip logic: Trip if a Delta Fault Forward AND a keyed channel is received.
This scheme is shown in the figure below.
P446SV Chapter 8 - Carrier Aided Schemes
P446SV-TM-EN-1 195
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