Research on the Characteristic of an Arc Device Equivalent to the Fire Source of the Cable Outer Sheath

Due to the failure of the grounding system of the armor layer of the cable, the suspension voltage of the outer sheath of the cable is too high, resulting in arcing, which is an important factor causing cable fires. In this paper, the distributed parameter model is first used to study the fire causes of the cable outer sheath. The results show that for a 110 kV cable, when the cable armor layer fails to ground, the voltage on the outer sheath can reach more than ten thousand volts, and the arc current is only mA level. Subsequently, the simulation test was carried out and the arc temperature was measured to be 2100 K, but the existing traditional fire source simulation method is difficult to reflect the characteristics of arc ignition. Therefore, this article adopts the way of climbing the ladder to generate arc, and its temperature is similar to the temperature of the test fire source, so it can be equivalent to the arc fire source of the cable outer sheath. Then, the characteristics of the arc device were studied, and it was shown that the electron density of the arc is on the order of 10
²¹
. And the smaller the electrode angle, smoother the electrode surface, larger the bottom distance or higher the applied arc current, the faster the climbing rate and the easier the arc is to climb to the top of the electrode. After entering the steady state, the shape and power of the arc fire source are affected by the arc current and the distance between the top electrodes. The larger the arc current or electrode distance, the greater length and height of the arc fire source, and the arc power is increased. So the control of the arc power can be realized through the calibration of the arc current and the electrode.