Functionality; Analog Channel Configuration; Operation Principle - ABB RELION REX640 Technical Manual

1MRS759142 C
4.3.4.3
4.3.4.4
4.3.4.5
REX640
Technical Manual

Functionality

The numerical stabilized low-impedance restricted earth-fault protection function
LREFPNDF for a two-winding transformer is based on the numerically stabilized
differential current principle. No external stabilizing resistor or non-linear resistor are
required.
The fundamental components of the currents are used for calculating the residual
current of the phase currents, the neutral current, differential currents and stabilizing
currents. The operating characteristics are according to the definite time.
LREFPNDF contains a blocking functionality. The neutral current second harmonic
is used for blocking during the transformer inrush situation. It is also possible to block
function outputs, timers or the function itself.

Analog channel configuration

LREFPDIF has two analog group inputs which must be properly configured.
Table 604: Analog inputs
Input
I3P
IRES
See the preprocessing function blocks in this document for the
possible signal sources.
There are a few special conditions which must be noted with the configuration.
Table 605: Special conditions
Condition
IRES measured
Improper analog channel configuration causes a validation error if the analog
channels are not completely configured or they do not match with certain settings. For
troubleshooting, check the contents of this chapter and also the preprocessing blocks
in this document. The configuration can be written to the protection relay once the
mismatch is corrected.

Operation principle

The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "on" and "off".
Protection functions
Description
Three-phase currents
Residual current (measured or calculated)
Description
The function requires that the current measured
from the neutral side is connected.
Section 4
661