Intelligent load shedding relay with disturbance detection scheme for power system protection.

摘要

The power distribution system may experience an abnormal frequency condition caused by loosing system generation and islanding of Distribution System Generators (DSG). In order to provide an accurate protection, it is necessary to differentiate the two conditions. Frequency relays with different settings are used for removal of pre-determined load to recover from the emergency generation deficiency condition. Other schemes are necessary for removing the islanding condition by separating the DSG from the system.; This thesis describes the design of intelligent load shedding relay which can differentiate the two conditions and activate the operation of corresponding functions. The relay has a unarmed frequency relay for normal operation and an armed frequency relay for islanding condition. The disturbance detector algorithm selects one of the relays based on phase shifts and frequency changes caused switching and faults on the power system. The multiple functions are based on the firmware and one common hardware. A description of hardware, real time software design and communication protocol is given.