87L provides selective protection for radial, looped and meshed network topologies and
can be used in isolated neutral networks, resistance grounded networks, compensated
(impedance grounded) networks and solidly grounded 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.
Communication
INCOMING
INCOMING
PROTECTED ZONE
RED 615 RED 615
GUID-E9D80758-16A2-4748-A08C-94C33997E603 V3 EN
Figure 240: Line protection with phase segregated line differential with in-zone
transformer
87L 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. 87L 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 use of 87L is not limited to these applications.
Section 4 1MAC059074-MB A
Protection functions
490 615 series ANSI
Technical Manual
To Next Page
Loading...
