IG-267-EN versión 01; 07/04/2017
23
General Instructions
ekor
.rpa
Protection functions
4.3. Directional units
The directional units are combined with the overcurrent
units when taking a decision on tripping. In accordance with
the "torque control" direction setting (
Forward
or
Reverse
)
and the result of the direction of the fault, the overcurrent
units finish by tripping or not.
The
ekor
.rpa-100 model 120 systems have the following
directional units:
• Three phase directional units (3 x 67)
• A neutral directional unit (1 x 67N)
• A sensitive neutral directional unit (1 x 67NS)
4.3.1. Phase directional units
Angular criterion
The phase directional units are units which, using the
angular criterion, determine the direction of each of the
3 phases. The polarisation voltage used for each phase is the
compound voltage corresponding to the other 2 phases.
These units determine direction based on:
• The calibrated settings.
• The phase difference existing between the polarisation
signal and the current signal.
The settings for the phase directional unit are:
•
Characteristic phase angle
: Characteristic angle
(from - 90.0
°
to 90.0°). This often corresponds to the
series impedance angle of the lines. Typical values in
distribution: 30° and 45°.
•
Minimum phases voltage
: Minimum polarisation
voltage (from 0.5 kV to 72.0 kV). Polarisation voltage
value as of which the directional unit considers the
angle reliable, and is capable of determining a direction.
•
Indeterminate zone
: Indeterminate zone angle (from
0.0° to 90.0°). Setting to establish the indetermination
zone which is close to the zero torque line.
The direction indicated by the units can be
Forward
,
Reverse
or
ndef
(undefined).
The Forward direction zone is delimited by the following
formula:
The
Reverse
direction zone will be the opposite of the
Forward
zone. In other words, the above formula needs to
be turned around 180° in order to achieve the expression
which delimits the
Reverse
direction zone.
The directional units will indicate
ndef
direction if in the
indeterminate zone or polarisation voltage is below the
V
min
setting.
The figure shows an example of operation of the directional
unit of phase A:
1
Reserve
2
Forward
3
Indeterminate zone
4
Zero torque line
5
Maximum torque line
Figure 4.3.
Phase A directional unit
Summary of Contents for ekor.rpa Series
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