Comparison of the Interrupting Capability of Gas Circuit Breaker According to SF6, g3, and CO2/O2 Mixture

Abstract

In the study, an interrupting performance test on the 145 kV gas circuit breaker is performed according to three different gases: SF6, g3 (5% NovecTM4710 with 95% CO2), and CO2(70%)/O2(30%) gases. Thanks to research advancements, it is confirmed that CO2 and g3 (5% NovecTM 4710) gases, respectively, have 40% and 75% dielectric strength, compared to that of SF6 gas. The filling pressure and transient recovery voltage criteria of each gas were determined differently in order to compare the maximum interrupting performance of each gas. The pressure of SF6 gas was determined to be 5.5 bar, which is typically used in circuit breakers. The pressure of the other two gases was determined to be 8.0 bar (the maximum available pressure of the test circuit breaker) to find the maximum interrupting performance. Moreover, the rate-of-rise of transient recovery voltage of SF6 was determined as 10 kV/μs, which is the value at the state of maximum interrupting performance of the test circuit breaker with SF6. On the other hand, the rate-of-rise of transient recovery voltages of g3 (5% NovecTM4710 with 95% CO2) and CO2(70%)/O2(30%) gases were, respectively, determined as 4∼5 kV/μs to find the interruption available point. The characteristics of arc conductance, arc current, and arc voltage near the current zero, and post-arc current are analyzed to compare the interrupting performance, according to different arc-quenching gases. The arc current is measured using a current transformer (Rogowski coil), and a signal processing method of the arc current and arc voltage is introduced to increase the reliability of the interrupting performance results. As a result of the test, it is confirmed that the critical arc conductance for all test conditions converged within a certain range and the value is around 0.7 mS. In addition, the critical current slope just before the current zero-crossing during the interrupting process is shown to be 1.8 A/μs between interruption success and failure. Consequently, it is verified that the CO2(70%)/O2(30%) mixture and g3 (5% NovecTM4710 with 95% CO2) have a similar arc extinguishing performance and SF6 has a relatively higher extinguishing performance than that of CO2(70%)/O2(30%) mixture and g3 (5% NovecTM4710 with 95% CO2) under the aforementioned filling pressure and TRV conditions.

Breakdown Initiation and Electrical Strength of a Vacuum Insulating System in the Environment of Selected Noble Gases at AC Voltage

“…Both sulfur hexafluoride and the aforementioned perfluorocarbons increase their temperature while residing in the atmosphere and thus create a greenhouse effect. This is evidenced, among others, by the GWP index (greenhouse effect potential), which is 22,200 for SF 6 , 5700 for CF 4 , and 9200 for C 2 F 6 [14].…”

A Method for Analysing and Characterizing the Arc Cooling Effect of Different Gases in Strong Axial Flow With SF6 and Air as Examples

“…On the switching side, it is a different story. While some test results were obtained [14] [15], the challenge is with the understanding and explanation of the differing interruption performances of different gases. It is evident that circuit breaker design has a significant influence on the interruption capability, however the fact that SF6 has been dominating high voltage switching applications is a far cry that it is the material properties that ultimately underpin its dominance.…”

Modelling G3 gas as an alternative gas for SF6 using COMSOL multiphysics

“…The first one is 4mol% Novec 4710+96% CO2 and the second ratio is 6mol% Novec 4710+94% CO2. These two ratios are the famous which used as alternative gas for SF6 gas [16], [17]. From Figure 3 when the fluoronitrile content reaches 18-20% in the new gas a pressure equal to1 bar then the dielectric strength will be equal to SF6 gas [11].…”