659 / 2017-05-18 08:51:15

Design and Test of Vacuum Circuit Breaker with Hybrid Fast Operation Mechanism

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With the demand for electrical power system expansion and intelligence, fast speed switching requirements is increasing in electrical transmission. The new requirements of high speeds witching have been put forward in many fields and situations such as fault current limiter, phase selection switch, double power switching device, DC circuit breaker etc. However, the closing or opening time of traditional switchgear driven by hydraulic mechanism or spring mechanism is longer. For example, the opening time of UHV circuit breaker relied on the hydraulic mechanism is up to 30ms and its closing time is nearly 120ms. The opening time of 12kV vacuum circuit breaker with spring mechanism is about 50 ms and its closing time is nearly 70 ms. With the rapid development of power grid, these mechanisms can’t meet the fast switching demands. It is necessary to develop switchgear with the fast driven mechanism.
The fast vacuum circuit breaker was designed, which was driven by the hybrid fast operation mechanism constructed with electromagnetic repulsion and permanent magnetic mechanism. The closing operation was driven by permanent magnetic mechanism, and the opening operation was driven by electromagnetic repulsion mechanism with double coil series, along with a spring. With the simulation of mechanism characteristics, the coil turns and wire diameter used in electromagnetic repulsion mechanism moving/motionless coil was obtained. Pure iron mixed with epoxy resin materials was selected as fixed permanent magnet coil skeleton material. Moreover，pure iron material was set as electromagnetic repulsion mechanism cover material. The effect on closing time by closing coil turns and wire diameter of permanent magnetic was analyzed. The simulation results have shown that fewer turns and the larger diameter can shorten the closing time. The relationship of permanent magnetic actuator armature shape with closing retention was investigated to use the T-shape armature. The cover structure and weight of permanent magnetic actuator were optimized. The closing bounce was simulated and the buffer mode to suppress closing bounce and opening rebound was determined to use double end points/closing hydraulic buffer device. The steel reinforced structure was inserted into the conductive rod in the arcing chamber was designed to add its strength, which can avoid the deform of the arcing chamber caused by the contacts impact.
Two12/40.5 kV prototypes of fast vacuum circuit breaker were developed. The product specifications referred to the existing standards of circuit breaker were formulated. According the new specification, type testing of the prototypes were carried out, including insulation, mechanical, temperature, main circuit resistance measurement, short time and peak current and the breaking level, etc. Test results have shown that the closing time of 12 kV prototype is no more than 10 ms, the opening time is no more than 3ms and the mechanical life times is 5000.The closing time of 40.5kV prototype is no more than15ms,opening time is no more than 5ms and the mechanical life times is 3000.These parameters meets the technical requirements. The switching time of fast circuit breaker can be greatly shorten with hybrid fast operation mechanism to satisfy the fast control and protection requirements of power grid.