ABB RELION REX640 Technical Manual page 644

Protection functions
4.3.1.2 Function block
Figure 360: Function block
4.3.1.3 Functionality
The line differential protection with in-zone power transformer LNPLDF is used
as feeder differential protection for the distribution network lines and cables.
LNPLDF includes low, stabilized and high, non-stabilized stages. The line differential
protection can also be used when there is an in-zone transformer in the protected
feeder section.
The stabilized low stage provides a fast clearance of faults while remaining stable
with high currents passing through the protected zone increasing errors on current
measuring. Second harmonic restraint insures that the low stage does not operate
due to energizing of a tapped or in-zone transformer. The high stage provides a
very fast clearance of severe faults with a high differential current regardless of their
harmonics.
The operating time characteristic for the low stage can be selected to be either
definite time (DT) or inverse definite time (IDMT). The direct inter-trip ensures both
ends are always operated, even without local criteria.
4.3.1.4 Analog channel configuration
LNPLDF has one analog group input which must be properly configured.
Table 645: Analog inputs
Input
I3P
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.
644
See the preprocessing function blocks in this document for the possible
signal sources.
Description
Three-phase currents
1MRS759142 F
REX640
Technical Manual