Monitoring functions
SIMOCODE pro
5-2 GWA 4NEB 631 6050-22 DS 03
5.1 Earth-fault monitoring
5.1.1 Description
SIMOCODE pro measures and monitors all three phase currents. By
evaluating the summation current of the three current values, the motor
feeder can be monitored for a possible fault current or earth fault.
Internal earth-fault monitoring via current measuring modules or current/
voltage measuring modules is only possible for motors with a 3-phase
connection in networks that are either grounded directly or with low
impedance.
Internal earth-fault-monitoring can be activated by means of
parameterization. It covers two different operating conditions.
• The normal operating condition up to 2 x I
s
. The effective operating current
must be smaller than twice the set current I
s
. Fault currents of > 30% of the
set current I
s
will be detected.
• Start-up or overload operation from 2 x I
s
. The effective operating current is
more than twice the set current I
s
. Fault currents of > 15% of the effective
motor current will be detected.
Note
If you use internal earth-fault monitoring for star-delta circuits, false tripping
may occur. During delta operation, the summation current is non-zero due to
harmonics.
External earth-fault monitoring via a summation current transformer and
an earth-fault module is normally used for networks that are grounded with
high impedance.
Rated fault currents of 0.3 A/ 0.5 A/ 1 A can be evaluated with the 3UL22
summation current transformer. The response delay of the summation
current transformer is 300 ms - 500 ms. This response delay can be further
delayed by parameterizing SIMOCODE pro accordingly.
A definable and delayable response can be parameterized when an earth
fault is detected.
An event is generated if the earth-fault limit is exceeded. You can set
additional trippings via parameterization.
If the rated fault currents are exceeded, SIMOCODE pro V reacts by either:
• Turning off the contactor controls QE, or
• By issuing a warning,
depending upon the configuration you have set.
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