Protection Based On Internal Calculation; Signal Flow Of The Internal Earth Fault Protection Function - ABB UMC100.3 Manual

C O N F I G U R I N G T H E M OTO R P R OT E C T I O N F U N C T I O N S

Protection based on internal Calculation

The UMC can detect an earth fault by summing up the three phase currents without using an external current transformer. The inter-
nal earth fault detection function signals a warning when the earth fault current exceeds a set threshold for a configurable period
of time, after the motor start-up. The earth fault detection function creates a trip when the current continuously exceeds a separa-
tely set threshold for a set period of time, after the motor start-up.
• Ground fault current must be > 20% of I
• Only usable in networks with low impedance to ground.
Only higher ground fault currents can be detected
• The set trip and warn levels should not be above 80% of I
• In case of fast starting motors without load an earth fault trip can happen during the start-up phase. Configure a
delay time in this case.
Block Diagram:
Vectorsum
I > Warn Thresh.
L1
I
L2
I
L3
Vectorsum
> Trip Thresh.
Always
>
After
start-up
—

Signal flow of the internal earth fault protection function

Relevant Parameters Internal Ground Fault:
• Earth Flt Trip Level
• Earth Flt Trip Delay
• Earth Flt Detection
If Trip Level and Warn Level = 255% then Earth Flt Level is not calculated.
If Trip Level or Warn Level is not 255% then Earth Flt Level is calculated and visible on panel or application.
& Ton
Earth Fault Warning
& Ton
Earth Fault Trip
• Earth Flt Warn Level
• Earth Flt Warn Delay
to be detected
e
e
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