NEW NOISE REJECTION TECHNIQUES ON PULSE-BY-PULSE BASIS FOR ONLINE PARTIAL DISCHARGE MEASUREMENT OF TURBINE GENERATORS

On-line partial discharge tests for turbine generators are useful for recognizing abnormal or deteriorated stator winding insulation without a machine outage. One problem related to such a test is additional in stallation of sensors, We propose that wires of a resistance temperatu re detector (RTD) embedded in a stator slot are applied as a partial d ischarge sensor in the form of an RF coupler, The other problem is ele ctrical noise that is a pulse similar to partial discharge in frequenc y characteristic and has higher amplitude than partial discharge, The sensors in two steam turbine generators showed enough sensitivity and broad frequency bandwidth to facilitate the elimination of noise from the partial discharge measurement, Two new techniques of noise rejecti on on pulse-by-pulse basis are investigated with the multiple sensors, One is founded on the correlation between pulse height in two frequen cy bands, The other is based on the correlation between pulse height f rom the two partial discharge sensors, It was found that each noise re jection technique was successful in a trial testing.