ABB RED615 Technical Manual page 351

1YHT530004D05 D
4.3
4.3.1
4.3.1.1
4.3.1.2
4.3.1.3
615 series
Technical Manual
Differential protection
Line differential protection and related measurements,
stabilized and instantaneous stages LNPLDF
Identification
Function description
Line differential protection and related
measurements, stabilized and
instantaneous stages
Function block
GUID-F7ECAC0B-14B5-444C-9282-59AC32380576 V3 EN
Figure 177: Function block
Functionality
The phase segregated line differential protection 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.
Protection functions
IEC 61850 IEC 60617
identification identification
LNPLDF 3dI>L
Section 4
ANSI/IEEE C37.2
device number
87L
345