Alstom MiCOM P545 - 1.15.1 Phase fault zone settings (Distance option only); 1.15.2 Ground fault zone settings (Distance option only)

P54x/EN OP/La4 Operation
(OP) 5-40 MiCOM P543, P544, P545 & P546
OP
Using the Advanced setting mode, the user has decided to set all the zones him/herself,
and must complete all the reach and residual/mutual compensation settings on a per zone
basis.
Note: Distance zones are directionalized (where applicable) by a delta
directional decision. The characteristic angle for this decision is set
along with the Delta Directional configuration, in the
GROUP x DISTANCE SETUP menu column. The default setting is
60
o
.
1.15.1 Phase fault zone settings (Distance option only)
Each
zone has two additional settings that are not accessible in the Simple set mode. These
settings are:
 A tilt angle on the top line of any quadrilateral set for phase faults;
 A minimum current sensitivity setting.
By factory defaults, the Top Line of quadrilateral characteristics is not fixed as a horizontal
reactance line. To account for phase angle tolerances in the line CT, VT and relay itself, the
line is tilted downwards, at a “droop” of -3
o
. This tilt down helps to prevent zone 1 overreach.
In Advanced setting mode, the Top line tilt is settable.
The current Sensitivity setting for each zone is used to set the minimum current that must be
flowing in each of the faulted phases before a trip can occur. If for example a phase A-B line
fault is present, the relay must measure both currents Ia and Ib above the minimum set
sensitivity. The default setting is 7.5% In for Zones 1 and 2, 5% In for other zones, ensuring
that distance element operation is not constrained, right through to an SIR ratio of 60.
1.15.2 Ground fault zone settings (Distance option only)
It should b
e noted that the Ground reach settings (Reach and Angle) are set according to the
positive sequence line impedance, and so will generally be identical to the Phase reach
settings.
The Top Line of ground quadrilateral characteristics is not fixed as a horizontal reactance
line. To account for phase angle tolerances in the line CT, VT and relay itself, the line is
tilted downwards, at a “droop” of -3
o
. This tilt down helps to prevent zone 1 overreach.
However, to further improve performance this line incorporates an additional dynamic tilt,
which will change according to the phase angle between the faulted phase current and the
negative sequence current:
 Zone 1 is allowed to tilt down to avoid overreaching for prefault power export;
 Zones 2 and 3 are allowed to tilt up to avoid underreaching for prefault power import.
As the tilt is dynamic, this is why ground fault elements do not have a setting for the angle.
The current Sensitivity setting for each zone is used to set the minimum current that must be
flowing in the faulted phase and the neutral
before a trip can occur. If for example an
A-ground fault is present, the relay must measure both currents Ia and Iresidual above the
minimum set sensitivity.
The default setting is 7.5% In for Zones 1 and 2, 5% In for other zones, ensuring that
distance element operation is not constrained, right through to an SIR ratio of 60.