Fracture analysis of fastening bolt of closing resistance for 1 100 kV GIS circuit breaker

Abstract

The contact of the closing resistance of a certain 1 100 kV circuit breaker is faulty. Two short bolts are falling off and two long bolts are broken and separated. By technical means of macro inspection， dimensional measurement， metallographic analysis and so on， the material， connection and operation conditions are discussed， the finite element analytical model with high precision is developed， and the fault cause is analyzed by considering the height difference of bolt hole between long bolt and short bolt and the impact of operation load. The results show that both long bolts and short bolts are intact， but the long bolts show obvious fatigue fracture morphology. Further analysis shows that when the closing resistance and the active arc contact press cylinder are fully fastened， the height difference of bolt hole between the long bolt and short bolt forms the tension， which loosens the long bolt and produces cracks at the connecting plate， thus the long bolts are broken under the action of long-term opening and closing. The height difference of the blot hole can be identified as the main cause of breaking of closing resistance fastening bolts.

Keywords

• ultra-high voltage
• circuit breaker
• closing resistor
• height difference of blot hole
• fatigue fracture
• finite element analysis