IG-150-EN version 04; 03/10/16
82
Protection functions. Description and settings
General instructions
ekor.rps
4.13. Isolated neutral protection
4.13.1. General description
The “Directional zero sequence relay” incorporated in the
relay carries out a directional protection against earth faults
in isolated neutral systems (67IN function). It can be used as
non directional.
1. Input signals
Zero sequence current (I
G
): Comes from the connection in
parallel of the secondaries of 3 phase current transformers or
from a toroid transformer embracing the 3 phases.
Zero sequence voltage (V
G
): If there are simple voltage signals
for each phase, it can be calculated internally. Other ways, it is
measured from the open delta of three voltage transformers,
with secondary nominal voltage of 110/√3 V. A setting
indicates which of the procedures is used.
2. Measurements range
Current: 2 mA to 1 A
Voltage: 0.5 V to 200 V (3*110/√3 V)
The characteristic curve of this protection function is the
following:
1
Trip zone
Figure 4.20.
Characteristic curve
They are settable parameters
1. Enable. If it is set to YES allows the protection units
actuation; set to NO inhibits the actuation and in pickup
it operates but without tripping.
2. Torque control (“external lock”). If it is set to “YES”, it
operates as directional, checking the angle between V
G
and I
G
; if it is set to “NO” it does not check the angle, that
is it works as non directional.
3. Low current (I
L
in the characteristic curve). Range 0.005
to 1 A, with 1 mA resolution.
4. High current (I
H
). Range 0.005 to 1 A, with 1 mA
resolution.
5. I
H
> = I
L
must be fulfilled
6. Low voltage (V
L
). Range 0.5 V to 60 V. 0.1 V resolution.
7. High voltage (V
H
). Range 0.5 V to 60 V. 0.1 V resolution.
V
H
> = V
L
must be fulfilled.
8. First trip timing. Range 0 to 60 s. 0.01 s resolution.
9. Switch to instantaneous timing. Range 0 to 10 s. 0.1 s.
resolution.
Operating as directional, the relay trips when the point
defined by the measured V
G
and I
G
values is within the
trip zone of the characteristic curve, being the DELAYED
with respect to V
G
an angle in the interval 90 º ± 45 º. As
“Non directional” the only trip condition is to be within the
characteristic zone, regardless of the angle.
The first trip is timed according to the corresponding
setting parameter, the successive trips that happen during
the time programmed as “switching time” starting from that
first trip are instantaneous; the first one from that time is
timed again.
4.13.2. Setting ranges
Parameter
Min
Max
Step
Notes
Enable
YES/NO
Torque control (external lock)
Low current [A]
0.005
1
0.001
High current [A]
0.005
1
0.001
Low voltage [V]
0.5
60.0
0.1
High voltage [V]
0.5
60.0
0.1
First trip timing [s]
0.00
60.0
0.01
Switch to instantaneous timing
0.0
10.0
0.1
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