Line current differential protection (CDP) is very suitable for active distribution networks (ADNs) with complex fault characteristics in principle, but its high cost limits its application. The dataself-synchronizat...
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Line current differential protection (CDP) is very suitable for active distribution networks (ADNs) with complex fault characteristics in principle, but its high cost limits its application. The data self-synchronization (DSS) methods do not require investing in additional synchronization equipment and provide a low-cost solution for line CDP in ADNs. However, the existing DSS methods based on time-domain features still have some shortcomings, such as they cannot be applied to lines with T-connected branches and are vulnerable to noise. In this paper, the existing DSS methods are first reviewed. On this basis, an improved DSS scheme based on reference phasor is proposed. This scheme calculates reference phasors based on the full-cycle data in a specific period before the fault and corrects the CDP criterion according to reference phasors. The proposed scheme includes three correction methods designed for lines without T-connected branches, lines with measurable T-connected branches and lines with unmeasurable T-connected branches, respectively. Finally, the performance of the proposed scheme is verified by an ADN simulation model based on PSCAD/EMTDC. Simulation results show that compared with existing DSS methods, the proposed scheme has the advantages unaffected by fault inception angles, better anti-noise ability, lower sampling frequency requirements, and wider application scenarios.
With the high penetration of distributed generations (DGs), the conventional radial distribution network is becoming an active distribution network (ADN). It has the characteristics of multisource, multibranch, bidire...
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With the high penetration of distributed generations (DGs), the conventional radial distribution network is becoming an active distribution network (ADN). It has the characteristics of multisource, multibranch, bidirectional power and fault current flow, as well as weak infeed. To provide effective protection for such a network, a novel current differential protection scheme, together with new implementation technology, is proposed in this paper. In this scheme, instead of using phase currents, a positive-sequence fault component (PSFC) is introduced into the differential protection. By building the PSFC equivalent circuit of the ADN, the distribution characteristic of PSFC within the ADN is theoretically analyzed in detail, especially for the case when the ADN contains inverter interfaced DGs. The PSFC-based differential protection criteria for different types of feeder are then established and simulated. To put the scheme into practice, data self-synchronization and peer-to-peer communication techniques are established. Based on this principle and using an advanced hardware platform, a protection prototype is successfully developed and tested. The test results verify the feasibility of the proposed protection scheme.
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