Alstom MiCOM P54 Series - 1.8 Earth fault distance protection (Distance option only); 1.9 Distance protection tripping decision (Distance option only)

Operation P54x/EN OP/La4
MiCOM P543, P544, P545 & P546 (OP) 5-31
OP
The protection elements are directionalized as follows:
 Zones 1, 2 and 3 - Directional forward zones, as used in conventional three zone
distance schemes. Note that Zone 1 can be extended to Zone 1X when required in zone
1 extension schemes.
 Zone P - Programmable directionality. Selectable as a directional forward or reverse
zone.
 Zone 4 - Directional reverse zone.
1.8 Earth fault distance protection (Distance option only)
The Mi
COM P54x has 5 zones of earth (ground) fault protection. It is also possible to set all
zones either with quadrilateral characteristics, or with mho circles. The choice of mho or
quadrilateral is independent of the general characteristic selection for the phase fault
elements. Each zone can be set independently to be permanently disabled, permanently
enabled or enabled in case of protection communication channel fail.
All earth fault distance elements are directionalized as per the phase fault elements, and use
residual compensation of the corresponding phase fault reach. The impedance plot
Figure 16 adds the characteristics
when set for quadrilateral operation.
P1135ENg
Directional
(reverse)
Directional
(forward)
Z4
Z1
Z2
Zp
Z3
(forward)
Figure 16 Earth fault quadrilateral characteristics (Distance option only)
1.9 Distance protection tripping decision (Distance option only)
For the Mi
COM P54x, five conditions would generally need to be satisfied in order for a
correct relay trip to result. These are:
 The phase selector needs to identify the faulted phases, and ensure that only the correct
distance measuring zones may proceed to issue a trip. Possible phase selections are
AN, BN, CN, AB, BC, CA, ABC. For double phase to ground faults, the selection is AB,
BC or CA, with N (neutral) just for indication only.
 The loop current for the selected phase-ground or phase-phase loop must exceed the
minimum sensitivity for the tripping zone. By default, this sensitivity is 5%In for ground
faults, and both of the faulted phases must exceed 5%In for phase-phase faults. The
user may raise this minimum sensitivity if required, but this is not normally done.