Earth Fault Protection; Signal Flow Of The Earth Fault Protection Function - ABB UMC100.3 Manual

U M C 1 0 0 . 3 U N I V E R S A L M O T O R C O N T R O L L E R T E C H N I C A L D E S C R I P T I O N
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Earth Fault Protection

The earth fault protection function protects the motor and the network against ground current flow. Earth faults are mainly caused
due to ageing of the insulation, deterioration of insulation due to sustained or cyclic overloading, moisture or conductive dust. The
monitoring of the earth fault is carried out with the help of the auxiliary device CEM11 or based on an UMC100.3 internal calculation
of the ground fault current. Detection of ground faults can be used to interrupt the motor to prevent further damage, or to alert
the maintenance personnel to perform timely maintenance.
Protection based on external earth fault detection device CEM11
The CEM11 device monitors if the sum of the three phase currents is zero. It is using a current transformer where all 3 phases are
fed through. The signalling output of the CEM11 can be connected to one of the multifunction inputs of the UMC.
The earth fault signal can be optionally delayed. It is also possible to suppress the earth fault during the motor start-up phase.
• CEM11 can be used in all types of networks (grounded or undgrounded)
• Can be used also in networks with higher impedance to ground. Also small ground fault currents can be detected
Block diagram:
CEM11 Signal
Ton
Suppress
during
start up
—

Signal flow of the earth fault protection function

Sample Circuit Diagram: To use CEM11 with the UMC proceed as follows:
1. Select the CEM11 model that suits your application needs. There are four different models available with feed-through holes
from 35 mm to 120 mm.
2. Connect the CEM11 to one of the multifunction inputs DI0, DI1 or DI2 and 24V DC supply.
3. Configure the corresponding multifunction input as earth fault input. You can select if the earth fault supervision shall be sup-
pressed during motor start or not.
4. Optionally a time can be configured to delay the creation of a fault or warning. It is adjustable from
5. Configure the threshold when an earth fault should be signalled. The threshold can be set directly at the earth fault monitor
(CEM11) itself. See the CEM11 technical manual for further details.
UMC100
10 11 13 14
DI0 DI1 DI2 DI3 DI4 DI5
0 V 24 V DC
Relevant Parameters CEM11:
• Multifunction Delay Time
• Multifunction Inputs 0,1, or 2
&
Earth Fault
Trip / Warning
3
15 16 17 18
3
M
0.1 to 25.5 s.