450 / 2017-05-02 12:11:08

Dielectric Recovery Property Measurements of CO2 and Air Arcs under Free Recovery Condition using Power Semiconductors.

SF6,361,Gas circuit breaker

Sulphur-hexafluoride SF6 gas is widely used as arc quenching medium in high-voltage circuit breakers. However, global warming potential of SF6 is 22,800 times higher than that of CO2. Thus, it is necessary to reduce the amount of SF6 use. For this reason, gas circuit breakers are strongly required to be downsized, and/or alternative gas for SF6 is also desired for arc quenching in a circuit breaker.
We have developed a new simple test technique to evaluate arc interruption ability of arc quenching gases by intentional application of current and voltage to the arc using power semiconductors. For the power semiconductors in this test, we use insulated gate bipolar transistors (IGBTs). The IGBTs were connected in parallel to the arc electrodes. Switching-on the IGBTs can make the arc current commutated to IGBT in several microseconds, which produces free recovery conditions accuracy in time. In addition to this, a voltage can be intentionally applied to the residual arc under free recovery condition between the electrodes by switching-off IGBT again after the specified timing td from the current commutation. This applied voltage is called “quasi transient recovery voltage (TRV)” because it is similar but different to regular TRV. From this test, we can evaluate successful interruption or interruption failure. In addition, we also conducted to observe the behavior of residual and re-ignition arcs with high speed video cameras.
Through the abovementioned quasi-TRV application tests, we estimated interruption probability versus the specified timing td of the quasi-TRV application. Also, we fundamentally measured dielectric recovery properties of CO2 and Air arcs under free recovery condition.