571 / 2017-05-15 10:46:03

Study on Temperature of Arcs Interacting with Different Gassing Material according to Spectroscopic Measurement

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会场 > Testing Technologies in Switchgears

The circuit breaker is an essential device for the electric power distribution network, as by separating two contacts, it switches off the current of the network in the event of short-circuit or overload. In many low voltage circuit breakers, ablated plastics or gassing materials are used in arc chambers to improve current interruption and current limiting capabilities. The temperature is a basic parameter of arc plasma property which give great help to extinguish arc. The experiments have been carried out in a low-voltage model circuit breaker, which contains an apparatus separating a copper electrode pair with a constant velocity (0.1m/s) by a DC electromagnet and a model chamber mounted with a strip of the gassing material. And an arc radiant spectrum collecting system was constructed including a lens, an optical fiber and a spectrograph. A breaking arc is generated in a circuit which is composed of a DC power supply, a 10Ω ceramic resistor, sample contacts and a complementary switch, and it is observed with a spectroscopic detecting system. The schematic diagram of the experimental system is shown in figure1.Three kinds of gassing material were used, two being organic-PA6 (C6H11ON,nylon), PMMA(C5H8O2,perspex) and the third ceramic. The samples were weighted before and after tests to obtain mass losses. A major assumption was that the temperature of the arc was constant during the exposure of spectrograms in which the intensity observations were made. The spectrum to be measured ranges from 396.78 to 599.99nm in wavelength in an interval of 1ms. Confirmation of the local thermodynamic equilibrium of a Cu arc column necessitates use of Boltzmann’s plots of spectral intensities at 510.5-nm, 515.3-nm and 521.8-nm wavelength (hereafter termed “CuⅠ510.5nm”, “CuⅠ515.3 nm” and “CuⅠ521.8 nm”) to calculate the temperature. A digital storage oscilloscope was used to record the waveforms of arc current and voltage, in synchronization with the spectrum collecting system. The optical spectrum in a three-dimensional display of wavelength, time, and light intensity was obtained in different materials and currents arranging from 3A to 10A. Spectra of Cu arc plasma for a current of 6A with the ceramic in the time of 100ms after breaking is shown in figure2. From the experimental result, the arc temperature variety curves were derived. The temperature is about 6719K. Correspondingly, the arc voltage transient curve is got with an identical time axis. Compared with ceramic, which is not sensitive to ablation, gassing materials such as PA6 and PMMA have an obvious influence on lowering arc temperature.