Protection Coordination of Biogas Power Plant Connected to Distribution Network

Over the past few decades, the need for proper protection coordination at the distribution level has increased due to the addition of distributed generation (DG) to radial distribution networks. In radial distribution networks the problem of coordination of overcurrent protection (OCP) devices does not exist- The relay, which is located at the furthest point from the source, is tripped in the shortest time. Other relays are tripped in a sequence with longer time delays, going back in the direction of the source. The paper presents the integration of the biogas (BG) power plant with the rated power of 1 MW to the Croatian distribution network. During the integration process the most important part on which the Croatian HEP Distribution System Operator (DSO) insists is the study of protection coordination. The protection coordination, and the antiisland protection, plays a significant role in the process of DG connection to the distribution network. The distributed generations from any type of renewable (PV, wind, biogas or biomass) power plant is not allowed to work in island with DSO in Croatia. Also the existing Network Grid Code does not allow islanding work too. This paper presents a protection coordination model of all the passive protection devices used in the real biogas power plant connected to the distribution network. The short-circuit currents for 3 phase fault (LLL) and single line to ground faults (SLGF) in the BG power plant and the surrounding distribution network are modelled and simulated. The protective devices are modelled with their real current-time characteristics. The protection coordination is performed using the SmartPDC-Smart Protective Device Coordination modules of the Easy Power Protector Software tool.