ABB RELION REX640 Technical Manual page 779

1MRS759142 F
flow into the protection zone, that is, currents with positive value, must be equal to
currents that flow out of the protection zone, that is, currents with negative value,
at any instant of time.
Figure 445
employing high-impedance differential protection. The example system consists of
a single incoming busbar feeder and two outgoing busbar feeders. The CTs from
both the outgoing busbar feeders and the incoming busbar feeders are connected
in parallel with the polarity. During normal load conditions, the total instantaneous
incoming current is equal to the total instantaneous outgoing current and the
difference current is negligible. A fault in the busbar results in an imbalance
between the incoming and the outgoing current. The difference current flows
through the protection relay, which generates a trip signal.
Figure 445: Phase-segregated single busbar protection employing high-impedance
differential protection
Figure 446
coupled with a bus coupler. Each busbar section consists of two feeders and
both sections are provided with a separate differential protection to form different
zones. The formed zones overlap at the bus coupler.
REX640
Technical Manual
shows an example of a phase segregated single busbar protection
shows an example for a system consisting of two busbar section
Protection functions
779