Application - ABB RELION REX640 Technical Manual

Section 4
Protection functions
4.3.1.7
582
GUID-7FC34CCB-60C2-415C-895E-1C63FD0874EC V1 EN
Figure 319: An example of a test mode situation where three-phase currents are
injected to the local end protection relay

Application

LNPLDF is designed for the differential protection of overhead line and cable feeders
in a distribution network. LNPLDF provides absolute selectivity and fast operating
times as unit protection also in short lines where distance protection cannot be applied.
LNPLDF provides selective protection for radial, looped and meshed network
topologies and can be used in isolated neutral networks, resistance earthed networks,
compensated (impedance earthed) networks and solidly earthed networks. In a typical
network configuration where the line differential protection scheme is applied, the
protected zone, that is, the line or cable, is fed from two directions.
RED 615
GUID-807098C6-1229-40A3-85F6-B7B02A9B3A2F V1 EN
Figure 320: Line protection with phase segregated line differential with in-zone
transformer
LNPLDF can be utilized for various types of network configurations or topologies.
Case A shows the protection of a ring-type distribution network. The network is also
used in the closed ring mode. LNPLDF is used as the main protection for different
sections of the feeder. In case B, the interconnection of two substations is done with
parallel lines and each line is protected with the line differential protection. In case C,
the connection line to mid scale power generation (typical size around 10...50 MVA)
is protected with the line differential function. The protection includes the transformer
from the protection field. In case D, the connection between two substations and a
Communication
PROTECTED ZONE
1MRS759142 C
RED 615
REX640
Technical Manual