A permanent magnetic actuator with scheduled stroke curve for vacuum circuit breakers
The load characteristics of vacuum circuit breakers (VCB) are very close to the output characteristics of permanent magnetic actuator (PMA). The combination of PMA and VCB facilitates the development of phase-controlled switching technology because of its controllability. The operation time dispersion of PMA is very small, but when the actuator is impacted by the change of environment or its components, its dispersion will be unfit for phase-controlled switching. A new type of actuator driving system for PMA was proposed, which was combined with sensors, embedded system and capacitor controlled by high-current power electronic devices. The iron core trajectory of PMA was measured by a displacement sensor and compared to a scheduled action curve, the environment temperature is from a temperature sensor and the current from a Hall current sensor, then compensation to displacement was made based on the adaptive control algorithm and history data in order to match the optimal stroke curve of vacuum circuit breakers. In different conditions, the test results show that the stroke curve was in keeping with the scheduled curve and the operating time dispersion of VCB meets the requirement. The new type actuator driving system can supply an easy-controlled, constant-operating- time execution unit to controlled switching.
Development of 550 kV and 362 kV synchronous switching gas circuit breakers
550 kV and 362 kV synchronous switching gas circuit breakers (GCBs) have been developed. In the closing operation of a GCB, making voltage depends on the rate of decrease of dielectric strength (RDDS) and the mechanical scatter of the operating time. No delay is caused by the operation after a long idle time up to 1000 hours, therefore optimal closing targets for different rated voltages can be determined by measurements on these characteristics of GCBs. Optimal target points for maximum and minimum making voltage are also given as functions of the RDDS and deviations of the operating time. The distribution of experimental maximum and minimum making voltages of synchronous closing with 550 kV and 362 kV GCBs shows good agreement with those calculated by the proposed method. A series of performance tests show that 550 kV and 362 kV GCBs can be applied for synchronous closing for transformer, reactor, capacitor, and line applications. The successful closing tests demonstrated the EMC of a synchronous switching controller mounted in a 550 kV GCB cabinet.
Field tests of a circuit breaker synchronous control
A circuit breaker synchronous control interface which controls the point-on-wave at which shunt reactor circuit breakers open or close has been developed and tested on Hydro-Quebec's 735-kV power system. It takes into account the influence of outdoor temperature on the breaker closing and opening times. It is also equipped with a reignition and a high-inrush-current detection system. Opening tests at different preset arcing times were conducted and the arcing time range where there are no re-ignitions in air-blast breakers was established. The tests showed that the interface is a valuable device for the elimination of re-ignitions associated with the interruption of small inductive currents. Closing tests have shown that the interface is also useful for the limitation of high inrush currents by selecting an appropriate point-on-wave for circuit breaker closing. >