• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.1100-1102
• /
• 2004

열팽창 방식의 가스차단기는 아크 에너지 자체를 이용하여 압력상승을 얻고, 상승된 압력을 이용하여 전류 영점 부근에서 아크 방향으로의 유동을 형성하여 아크를 소호한다. 대전류 구간에서 노즐 폐색현상이 일어나면 노즐 용삭이 크게 일어나며 용삭된 노즐 물질은 팽창실의 압력과 온도를 상승시키게 된다. 따라서 차단 특성해석을 위해서는 노즐 용삭에 의한 압력 상승해석이 필요하다. 본 논문에서는 아크에너지에 따른 노즐 용삭비를 이용하여 용삭되는 노즐량을 계산하고, 이로 인한 back flow현상을 고려한 해석 방법을 제안한다. 개발된 프로그램을 제작한 차단부 모델에 적용한 결과, 열팽창실의 압력상승치는 시험결과와 잘 일치함을 확인하였다.

• Proceedings of the KIEE Conference
• /
• 2003.07b
• /
• pp.982-984
• /
• 2003

본 논문에서는 계통에서 사고에 의해 발생한 고장전류를 차단할 때, 가스차단부에서 발생하는 고온 고압의 아크플라즈마 하에서 노즐용삭에 의해 PTFE와 같은 노즐 물질이 $SF_6$가스에 혼입하는 경우에 노즐 재질이 아크플라즈마의 차단특성에 미치는 영향을 평가하기 위해 요구되는 과도상태 노즐용삭 해석기술에 대하여 정리한다. 그리고 노즐용삭 해석기술을 계통에서 고장이 발생한 경우에 흐르는 고장전류를 차단하는 과정에서 발생하는 아크플라즈마에 적용하여 용삭된 PTFE의 농도를 계산하고 그 결과를 제시한다.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.846_846
• /
• 2009

노즐의 용삭은 초고압 가스 차단기의 압력 상승에 중요한 역할을 한다. 기존의 연구는 총 아크 에너지와 용삭량과의 관계에 집중되어 왔으며 아크 에너지 대신 전류의 제곱등을 사용하기도 했다. 본 논문에서는 반복 시험을 통해 노즐 용삭 특성을 구하였으며, 이를 통해 아크의 전류, 전압과 용삭량과의 상관관계를 구하였다. 또한 계단형 노즐을 사용하여 노즐 반지름과 용삭량과의 관계에 대해서도 살펴보았다.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.695-698
• /
• 2008

Self-blast circuit breakers utilize the energy dissipated by the arc itself to create the required conditions for arc quenching during the current zero. During the arcing period, high pressure, temperature and radiation of the arc could burn in pure SF6 gas and PTFE nozzle. Ablated nozzle shape and $SF_6$-PTFE mixture vapor affect the performance of an self-blast circuit breaker. After a number of tests, nozzle in circuit breaker is disassembled, a section of ablated nozzle is investigated precisely. Using computational fluid dynamics, the conservation equation for the gas and temperature, velocity and electric fields within breaker is solved. Before applying a section model, developed program is verified with experimental data. Performance of ablated nozzle shape is compared with original model through analysis program.

• 한국전산유체공학회:학술대회논문집
• /
• 2005.10a
• /
• pp.311-317
• /
• 2005

It has been the most progressive interruption technique to use the ablation gas from the surface of PTFE nozzle driven by arc plasma during switching process in $SF_6$ gas circuit breakers. This advanced interruption technique can reduce the required mechanical energy to compress and blow the gas for extinguishing the arc plasma between the electrodes due to using the ablation effect instead. In order to consider the phenomena during calculation of switching process, it is required to confirm the principles of ablation from PTFE nozzle as well as of arc plasma during switching process. In this study, we have calculated the switching process considered the ablation of PTFE nozzle driven by arc plasma using multidisciplinary simulation technique and compared the results with the data without the ablation effect. More $50\%$ difference of pressure rise inside expansion chamber has been found from the results and it should be indispensable for this type of computational work to consider and include the ablation effect of PTFE nozzle. Further study on turbulence and radiation will be followed.

• Proceedings of the KIEE Conference
• /
• 2002.07b
• /
• pp.622-624
• /
• 2002

This paper describes a method for steady state hot gas flow analysis considering nozzle ablation for the nozzle of $SF_6$ gas circuit breaker. In order to take account of the effect of ablated nozzle material on the hot gas flow. the PTFE mass concentration equation is added to the established equations for hot gas flow analysis. The steady state simulations were carried out under the condition of DC current flows and the results are presented.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.2506-2511
• /
• 2007

The coupled simulation is performed to find out the interaction of arc plasmas with surrounding materials in a thermal puffer plasma chamber. In order to be more realistic, PTFE nozzle ablation and Cu electrode evaporation, which are caused by high temperature of arc plasmas, are considered together. Pressure rise and temperature inside the chamber generated during the whole arcing history are investigated with the applied currents. It is very important to define how thermal flow and mass transfer are processing between the arc plasma and surrounding materials for further understanding complex physics inside the chamber. It is concluded that the result might be very useful to understand the mechanism happened inside and to design thermal puffer plasma chambers, but further experimental studies are required to verify the results for the more practical applications.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.2494-2499
• /
• 2007

Self-blast circuit breakers utilize the energy dissipated by the arc itself to create the required conditions for arc quenching during the current zero. The high-current simulation provides information about the mixing process of the hot PTFE cloud with $SF_6$ gas which is difficult to access for measurement. But it is also hard to simulate flow phenomenon because the flow in interrupter with high current, $SF_6$-PTFE mixture vapor and complex physical behavior including radiation, calculation of electric field. Using a commercial computational fluid dynamics(CFD) package, the conservation equation for the gas and temperature, velocity and electric fields within breaker can be solved. Results show good agreement between the predicted and measured pressure rise in the thermal chamber.

• The KSFM Journal of Fluid Machinery
• /
• v.11 no.4
• /
• pp.7-13
• /
• 2008

The computational investigation is performed to find out the interaction of arc plasmas with surrounding materials and the thermal flow characteristics in a PASB (Puffer-Assisted Self-Blast) chamber, which is one of new breaking concepts in $SF_6$ switchgears. It is very important to define the flow and mass transfer happened during the full arcing history for further understanding complex physics inside the chamber. In this study, we have considered two diffusion processes by the hot arc plasma, one is PTFE nozzle ablation and the other is Cu electrode evaporation, simultaneously. It was found that the principle of the pressure-rise inside the chamber is confirmed by the computational results and the increase of the electrical conductivity of the residual gas near current zero is critical to the chamber design.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.54 no.2
• /
• pp.76-82
• /
• 2005

In this paper, a method for analyzing the thermal recovery characteristics of the nozzle of gas circuit breaker was described. In order to obtain thermal recovery characteristics, the transient simulation of SF6 arc plasma within the nozzle was carried out. In particular, the nozzle ablation was taken into account by simultaneously solving the PTFE concentration equation with the governing equations such as continuity, momentum and energy equation. After that, post arc current calculation was performed with the rate of rise of recovery voltage changed. From the calculated post arc current, it was possible to suggest the thermal recovery characteristics of the nozzle of gas circuit breaker.