Study On The Breaking Characteristics Of 550kV Single-Break Self-Blasting Circuit Breaker

In recent years,the rapid development of the UHV industry has brought huge profits to the transmission and transformation equipment market and it has greatly led the development of transmission and transformation equipment.Puffer type SF₆ circuit breaker occupies a dominant position in the high-voltage circuit breaker market due to its excellent breaking and insulation performance.Since the puffer circuit breaker needs the cylinder to continuously work on the gas in the cylinder during the breaking process especially for the UHV circuit breaker,a high-power operating mechanism is required to complete the breaking task.The self-blasting circuit breaker can make up for this deficiency due to its small size and low operating power.At present,due to insufficient knowledge of the arc theory,the further development of high-voltage self-blasting circuit breakers has been limited.Most of the circuit breakers used in 550kV are puffer type SF6 circuit breakers,which need large equipment and high operating power.Therefore,the study on the high-voltage large-capacity self-blasting arc chamber has become an important part of achieving the goal of"self-blasting"in UHV circuit breakers.This subject relies on the science and technology project of State Grid Corporation"Study on the Key Technology of 550kV Single-Break Self-Blasting Arc Chamber".This subject takes a 550kV single-break self-blasting circuit breaker as the research object and establishes a two-dimensional dynamic arc mathematical model considering the nozzle ablation.This paper stem from three aspects:the breaking characteristics of small current,the breaking characteristics of large current and study on the influencing factors of breaking characteristics.In terms of small current,the paper considers the insulation characteristics of the arc chamber,the pressure and medium recovery characteristics under small capacitive current,and the pressure and temperature characteristics under the condition of 10%rated short circuit current.In terms of large current,the paper studies the effects of different short-circuit currents,different arcing times and nozzle ablation on pressure and temperature characteristics.The breaking performance is compared and analyzed by the distribution of flow parameters between the breaking gap at the time of current zero.In addition,this paper also studies the action characteristics of the valve and the compression work characteristics of the cylinder,and compares and analyzes the difference between the puffer type structure and the self-blasting type structure.Finally,the effects of different nozzle expansion angles,expansion chamber volume and inflation pressure on breaking characteristics are compared and analyzed.The results show that under the condition of breaking small capacitive current,the shortest arcing time that can be successfully interrupted is 2ms.Under large current breaking conditions,the larger the current value,the stronger the breaking performance and the greater the nozzle ablation quality;while the longer the arcing time,the weaker the breaking performance,but the larger the nozzle ablation quality and the pressure in expansion chamber won’t larger.The short-circuit current and arcing time have less influence on the acting time of the valve.Nozzle ablation contributes less to the pressure in expansion chamber,but will reduce the average temperature of the arc zone by 3000K-5000K and the medium recovery capacity after the arc will be correspondingly improved.Compared with the puffer type cylinder,the self-blasting cylinder can reduce the compression work about24%at least and the compression power can be reduced by about 25%-40%.Combining several calculation conditions in this article,the existing design scheme,that is,the downstream expansion angle of the 50°nozzle,100%expansion chamber volume and the inflation pressure of 0.65MPa can achieve a relatively good breaking performance.