Methodology of Automated Protection Analysis for Large Distribution Feeders With High Penetration of Photovoltaic Systems

This paper presents highly automated methods to study the protective device coordination in large distribution systems with high penetration of distributed photovoltaic (PV) generation. A real distribution feeder with large-scale distributed PV generation has been modeled and verified using the analysis tool OpenDSS and utilizing extensive field measurements. With the accurate and validated feeder model, thorough protection coordination of the system is investigated by applying all the possible phase and ground faults under various scenarios. Under varying PV penetration levels and with different PV interface transformer connections, settings for the phase and ground relay and recloser are verified/defined, such that proper coordination is achieved for the entire feeder under all operating conditions, corresponding to both fuse-clearing and fuse-saving schemes. An optimization-based design of protective devices is introduced that ensures proper protection coordination under thousands of possible fault cases. The automated protection analysis has been implemented using OpenDSS with the MATLAB COM interface, and this approach and these tools can be extended to analyze and design protection coordination of any large distribution feeder, as well as to use as a screening tool while evaluating large scale PV on distribution feeders.