Study on stability check of high impedance differential protection for large motors

For the problem of large motor protection in nuclear station,the stability check method of high impedance differential protection for large motors is presented. The effect of current transformer( CT) excitation inflection point,CT turns ratio error and CT loop cable resistance on the high impedance differential protection of large motors is analyzed. The test method of stability check for the high impedance differential protection is also introduced,which is then tested on the actual large motor. The evaluation of protection setting calculation is verified according to the actual motor dynamic simulation test. At last,the test result is obtained with test data analysis.