Figure 161: Overcurrent protection of parallel lines using directional protection
relays
DPH3xPDOC can be used for parallel operating transformer applications. In these
applications, there is a possibility that the fault current can also be fed from
the LVside up to the HV-side. Therefore, the transformer is also equipped with
directional overcurrent protection.
Figure 162: Overcurrent protection of parallel operating transformers
Closed ring network topology
The closed-ring network topology is used in applications where electricity
distribution for the consumers is secured during network fault situations. The
power is fed from at least two directions, which means that the current direction
can be varied. The time-grading between the network level stages is challenging
without unnecessary delays in the time settings. In this case, it is practical to
use the directional overcurrent IEDs to achieve a selective protection scheme.
Directional overcurrent functions can be used in closed-ring applications. The
arrows define the operating direction of the directional functionality. The double
arrows define the nondirectional functionality where faults can be detected in both
directions.
Protection functions
1MRS757644 H
316 620 series
Technical Manual
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