Aided Def Blocking Scheme; The Def Permissive Scheme; Independent Channel – Blocking Scheme - GE MiCOM P40 Agile Technical Manual

P44x/EN AP/Hb6
(AP) 5-108
A
Figure 82: The DEF permissive scheme
The scheme has the same features/requirements as the corresponding distance scheme
and provides sensitive protection for high resistance earth faults.
Where "t" is shown in the diagram this signifies the time delay associated with an element,
noting that the time-delay for a permissive scheme aided trip would normally be set to zero.
4.8.3.2.2

Aided DEF Blocking Scheme

Figure 85 shows the element reaches, and Figure 86 the simplified scheme logic. The
signalling channel is keyed from operation of the reverse DEF element of the relay. If the
remote relay forward IN> element has picked up, then it will operate after the set time delay
if no block is received.
Figure 83: Independent channel – blocking scheme
MiCOM P40 Agile P442, P444
IN> Fwd (A)
ZL
IN> Fwd (B)
Application Notes
B
P3070EN