1) Insulation performance. According to the internal structure of the circuit breaker, combined with different dielectric constants of SF6, epoxy resin and ceramics, an electric field simulation model was established, and the insulation characteristics were analyzed and calculated. The arc-break chamber fracture is calculated by applying a 2400kV lightning impulse voltage to one end and applying a power-frequency voltage with a reverse polarity peak of 635kV at the other end, that is, 900kV, which is the most demanding condition. The product structure is optimized according to the electric field requirements, and the test verification meets the insulation requirements. 2) Breaking capacity. On the basis of the breaking capacity 50kA circuit breaker, the structure of the arc extinguishing chamber is optimized. Considering the effects of the opening speed, the volume of the compressor chamber, the shape of the nozzle and the breaking current, the gas pressure in the process of breaking the 63kA short circuit current of the circuit breaker was simulated and analyzed, and the air chamber and the nozzle were obtained. The ideal air pressure. Through the performance verification test conducted by the circuit breaker prototype, the parameters such as opening speed, arcing time, arcing interval and pre-breakdown time were improved. The type test results show that the developed UHV circuit breaker has superior large short-circuit current breaking capability. 3) Operating mechanism. The UHV circuit breaker uses a high-power hydraulic operating mechanism, which places high demands on operational characteristics and stability. On the basis of the hydraulic mechanism of the UHV circuit breaker with a breaking capacity of 50kA, according to the modular design, the output power of the mechanism is increased, and the high-flow quick-acting valve, the integrated multi-stage buffer system, and the sealing structure in the form of grid ring and seal are used. By optimizing various structural parameters, excellent mechanical properties are obtained, and the operating speed is adjustable. 4) Short-circuit breaking test technology. The short-circuit breaking test of the UHV circuit breaker in China adopts the current introduction synthesis test method. The test current is appropriately adjusted to introduce the current and frequency of the voltage source to meet the requirements of the zero zone assessment equivalence. When the rated voltage is higher than 800kV, the test equipment of the current introduction method reaches the limit and cannot meet the requirements of the integral test of the UHV circuit breaker. To this end, a synthetic test loop of the "three-loop method" was proposed. In the high current phase, the current through the sample is supplied by the current source, and the first set of voltage loops is input at the appropriate time before the zero-crossing break, and the current supplied by the current source and the first set of voltage loops flows through the circuit breaker under test; After the zero-crossing of the product, the first set of voltage loops provides the TRV starting part at one end of the circuit breaker. When the TRV rises to a certain stage, the second set of voltage loops is applied and simultaneously applied to the other end of the circuit breaker and the outer casing. The voltages of the voltage loops are superimposed to form the recovery voltage applied to both ends of the sample, and the full voltage evaluation of the casing is satisfied; in the circuit switching, the equivalence requirement of the current zero zone should be ensured. The "three-loop method" synthetic test circuit has good equivalence and high safety, and successfully completed the whole machine breaking test of T100s and T100a of 1100kV circuit breaker.
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Indispensable electrical equipment in UHV transmission and transformation - circuit breaker
The voltage of the UHV circuit breaker is high, the short-circuit breaking current is large, the DC component decay time constant is 120ms, and the breaking is difficult. It is necessary to establish a test circuit equivalent to the actual breaking condition, which puts forward higher requirements for the breaking test and needs to be carried out. Insulation, short-circuit breaking and test technology research. In-depth research on the insulation performance, breaking capacity and test technology of the circuit breaker has been carried out in China, and an ultra-high voltage circuit breaker with double-break/four-break and 63kA breaking capacity has been developed.