ABB RED615 Technical Manual page 380

Section 4
Protection functions
374
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.
GUID-E9D80758-16A2-4748-A08C-94C33997E603 V2 EN
Figure 197: 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 small distribution transformer is located
at the tapped load. The usage of LNPLDF is not limited to these applications.
1YHT530004D05 D
615 series
Technical Manual