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Estimating arc temperature in a model high breaking capacity fuse

Summary We present estimates of the temperature at different times during the arcing period of an experimental model of a sand-filled, high-voltage, high breaking capacity fuse. The model fuse does not interrupt current automatically but the technique described here could well be used in actual current-limiting high-voltage fuses to measure the time-resolved arc temperature. The test fuse is energized using a synthetic test circuit which supplies the fuse a prospective current of.5 kA at 6 kV, 50 Hz. An optical fibre is used to carry light from the fuse’ arc to a spectrograph which is used to isolate spectral lines of interest. The spectrum is recorded by an intensified photodiode array. By gating the image intensifier in front of the diode array a complete spectrum is recorded in several microseconds. By varying the timing of the gate pulse the arc spectrum can be obtained at any desired time during the arcing period. The arc temperature is determined from the relative intensities of Si II spectral lines. The arc temperature is found to vary between 7,000 and 27,000 K at different instants during the arcing period.