Anti-Islanding Protection Relay for Medium Voltage Feeder with Distributed Generator

Large distributed generators such as solar farms and wind farms are usually connected to medium voltage feeders. The anti-islanding protection for medium-voltage (typically up to 50 kV) DG relies on the transfer trip from transformer station. This paper presents a local anti-islanding protection relay as a backup for transfer trip in case of failures. The anti-islanding detection scheme is to short the phase or line voltage at the point of common coupling when voltage crossing zero, and then detects the current in thyristor to determine the operating mode of the DG units. This proposed scheme has been evaluated using analytical, simulation and experimental test. The results show that the proposed scheme features high performance, low cost and high neutrality. It has the ability to protect against islands operation of DG units.