ABB RED615 Technical Manual page 224

Section 4
Protection functions
218
is a risk that the fault situation in one part of the feeding system can de-energize the
whole system connected to the LV-side.
GUID-1A2BD0AD-B217-46F4-A6B4-6FC6E6256EB3 V2 EN
Figure 112: Overcurrent protection of parallel lines using directional IEDs
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 LV-
side up to the HV-side. Therefore, the transformer is also equipped with directional
overcurrent protection.
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Figure 113: 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
1YHT530004D05 D
615 series
Technical Manual