Abstract: Abstract:In order to increase the power transmission capacity, the series compensation devices were installed for the four output transmission lines of Togtoh Power Generation Company Limited. In order to restrain the subsynchronous resonance, which occurred after the series compensation devices were put into operation, the blocking filters were added to neutral point sides of each phase of each main transformer. In the same time, the unit shaft system torsional vibration protection and the asynchronous selfexcitation protection were configured. The reasons of subsynchronous resonance and the adopted targeted restraining measures were expounded. By means of analysis on actions of unit shaft system torsional vibration protection and the asynchronous selfexcitation protection under abnormal system operation condition, the effect of the blocking filter to restrain subsynchronous resonance was verified.

Key words: Key words:subsynchronous resonance, torsional vibration of shaft system, asynchronous selfexcitation, blocking filter