Principle and Implementation of Networked Protection in Active Distribution Networks

The performance of conventional protections has deteriorated in active distribution networks (ADN) because of high penetration of distributed generator (DG) and solid state transformer (SST). In this paper, based on the features of short-circuit current fed by DG and SST, the current distribution characteristics of ADN are analyzed. Moreover, a networked protection scheme is proposed for ADN. This scheme compares the amplitudes of negative-sequence, zero-sequence and phase currents between different ports of grid component to realize fault identification. It can act rapidly and has the ability to cope with large transition resistance. Communication system only needs to transmit current amplitude, and synchronous sampling is not required. In addition, there is no requirement for voltage measurement, which will help to reduce cost. The effectiveness of the protection scheme is verified via simulation tests.