Earth Fault Monitoring In It (Ungrounded) Systems (+Q954); What This Chapter Contains; To Which Drives This Chapter Applies; Earth Fault Protection In Tn (Grounded) Systems - ABB ACS800 Series Hardware Manual

Earth fault monitoring in IT (ungrounded) systems
(+Q954)

What this chapter contains

This chapter describes earth fault monitoring option +Q954 in IT (ungrounded)
systems. The chapter deals with applicability, wiring, operation and use. Example
circuit diagrams are included. The chapter also describes the internal earth fault
protection of the drive in short.

To which drives this chapter applies

The chapter applies to the following drives:
Drive type
ACS800-07
ACS800-U7
ACS800-17
ACS800-37

Earth fault protection in TN (grounded) systems

AC fuses

The supply AC fuses protect the drive against a direct earth fault in the supply or
intermediate DC circuit in case the fault current exceeds the operating current of the
fuse.

Internal earth fault protection of the ACS800-02/U2/07/U7

The drive is equipped with a hardware and software based earth fault protection
against earth faults in the motor cable or motor. The output currents of the drive are
measured by current transducers and added up. The current sum is normally close
to zero. In case of an earth fault, current i produces over resistor R
is measured by the AINT board. A signal is sent to the RMIO board. If the measured
voltage exceeds the set limit, an earth fault warning or trip is produced, depending
on a parameter setting of the application program.
In parallel-connected inverters, the sum current measurement is located at the
output of each inverter. One RMIO board produces an earth fault warning or trip,
whenever the current sum of an inverter exceeds the set limit.
Frame sizes Option code and description
R6, R7, R8; +Q954 = earth fault monitoring for IT (ungrounded) systems
n×R8i
R6i, R7i, n×R8i

Earth fault monitoring in IT (ungrounded) systems (+Q954)

83
a voltage which
T