Development of microprocessor based negative phase sequence current monitoring unit and negative phase sequence relay for an ac generator

摘要

The existing protection schemes for unbalance stator current in an ac generator are based on extraction of negative phase sequence (NPS) components by suitable fih6sfrom the stator current. In the present investigation, the development of NPS current in the rotor circuit during stator unbalance has been analysed theoretically and studied experimentally. This NPS current has been sensed directly with the help of a microprocessor which measures the magnitude of the peak values and generates a trip signal according to the (I{sub}2 ～ t) characteristic of the generator winding. The developed scheme has been tested in the laboratory and the experimental results have been presented.