Design
The earth fault and short circuit indicator consists of:
3 pcs. short circuit sensors
1 pc. earth fault sensor
1 pc. reading instrument
connecting cables
The reading instrument is
incorporated in a plastic housing together with the electronics for the
time reset and the evaluating electronics.
Each type of fault, short circuit and earth fault, is indicated by one
blinking LED.
The fault is remotely indicated over one relay (1x changer) for earth
fault and short circuit.
The reading instrument is equipped with a test/reset button.
Each sensor consists of a plastic housing, which contains a coil to
detect impulses caused by a short circuit or an earth fault. The
housing is fully sealed and follows the standards of IP 67.
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Function
The
sensors detect earth faults and short circuits inductively. The
operating points for earth fault and short circuit are adjusted with
electronics for threshold levels. When the current picked up by the
coil exceeds the preadjusted threshold level,
an impulse is sent to the reading instrument for evaluation. The
respective LED indicates a short circuit and/or an earth fault.
Minimum impulse adjustment: The reading instrument is equipped with a
setting for minimum impulse duration.
The impulse picked up from the sensor is evaluated regarding its
duration. If the impulse duration is shorter than the adjusted value of
the mininum impulse duration, no fault will be indicated. If the
impulse duration is longer than the preadjusted duration, an earth
fault or short circuit is indicated.
This equipment allows the filtering of peak current caused by switch
currents or similar circumstances. Wrong indications are thus avoided.
With the instrument 4 values for minimum impulse duration can be
adjusted (times follow request of customer).
The reset of the earth fault or
short circuit indication can be done by:
a) automatic time reset. A time element controls the indication and
resets it after a preadjusted time
(4 values between 0.5 h to 40 h are selectable).
b) manual reset with a push-button.
c) recovering net voltage (if the reading instrument is supplied from
the monitored net).
Assembling
-
Please refer to the assembling instructions delivered with each
instrument -
The reading instrument has to be installed outside the high voltage
area. The short circuit sensors and the earth fault sensor must be
installed on screened, earthed cables. The earth fault sensor must be
installed around all three cores to assure that the sum current of all
three cables is picked up.
The frames of the sensors can be opened for installation.
The short circuit sensors the earth fault sensor are connected to the
reading instrument via cable.
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