To study the contact erosion characteristics of SF

6

circuit breaker during opening operation

the erosion test was conducted on the tested SF

6

circuit breaker and the dynamic resistance curves as a function of contact travel was obtained in different levels of degradation of contacts by dynamic contact resistance measurement. Some parameters of contact condition were extracted from the curve. According to the variation of these diagnostic parameters

the following results can be obtained. A minimum value of contact travel is obtained to be 14.2 mm.The value of contact resistance has a standard range

which is 50

1

50 mW for main contact and 200

4

00 mW for arcing contact.The length decrement of arcing contact is 0.318 mm for

each erosion test. According to these results

we analyzed the contact material erosion process during the opening operation and the impact on the circuit breaker characteristics. Meanwhile

the length decrement of arcing contact for each erosion test is calculated to be 0.268 mm

which is close to the measured value of 0.318 mm. Eventually

the preliminary prediction method for the electrical life of SF

6

circuit breaker was summarized.