2.11 Undercurrent protection I< (37)
2 Protection functions
Technical description
62
VAMP 24h support phone +358 (0)20 753 3264
VM50.EN004
2.11.
Undercurrent protection I< (37)
The undercurrent unit measures the fundamental frequency
component of the phase currents.
The stage I< can be configured for definite time characteristic.
The undercurrent stage is protecting rather the device driven
by the motor e.g. a submersible pump, than the motor itself.
Parameters of the undercurrent stage I< (37):
Parameter Value/unit Description
Measured
value
ILmin A
Min. value of phase currents
IL1…IL3 in primary value
I<
xImode
Setting value as per times Imot
Setting
values
t<
S
Operation time [s]
SCntr
Start counter (Start) reading
TCntr
Trip counter (Trip) reading
1-N, 2-N
3-N
Fault type/single-phase fault
e.g.: 1-N = fault on phase L1
1-2, 2-3
1-3
Fault type/two-phase fault
e.g.: 2-3 = fault between L2 and
L3
Type
1-2-3
Fault type/three-phase fault
Flt %
Min. value of fault current as
per times Imot
Load %
1s mean value of pre-fault
currents IL1—IL3
Recorded
values
EDly %
Elapsed time as compared to
the set operate time, 100% =
tripping
2.12.
Directional earth fault protection
I
0
φ
> (67N)
The directional earth fault protection is used for earth faults in
networks or motors where a selective and sensitive earth fault
protection is needed and in applications with varying network
structure and length.
The device consists of versatile protection functions for earth
fault protection in various network types.
The function is sensitive to the fundamental frequency
component of the residual current and zero sequence voltage
and the phase angle between them. The attenuation of the
third harmonic is more than 60 dB. Whenever the size of I
0
and
U
0
and the phase angle between I
0
and
U
0
fulfils the pick-up
criteria, the stage picks up and a start signal is issued. If the
fault situation remains on longer than the user's operation time
delay setting, a trip signal is issued.