Arc-fault simulator platform

Experiments on the thermal behavior of arc-fault were conducted using a DC arc-fault simulator as shown in Fig 1. The main circuit, consists of a DC power supply, resistor array and an arc-fault simulator, is shown in Fig 1(B). The DC power supply (ETS-1000X10 from Ametek, America) could provide a variable DC voltage U with a maximum 1000 V and uncertainty within 0.2%. The resistor array was made of several high power corrugated resistors (with electric resistance 20 Ω and maximum power 2000 W, from GEE Electronics, China) by series connection. The total resistance R could be altered by changing the number of corrugated resistors (e.g., R was adjusted to be 40 Ω, 60 Ω and 80 Ω during tests, respectively). A Hall effect current sensor (CHB25-NP from Sensor Electronics, China) was used to measure the current I variation in circuit with a maximum 25 A and uncertainty within 0.8%. The current I and arc voltage U_a were both recorded by an oscillograph (DPO4010B-L from Tektronix, America) online. In order to obtain high quality data, the sampling frequency was chosen to be 100 Hz.

Experimental setup (a) and sketch of main circuit (b) with arc-fault simulator (c).

A more detailed diagram of the arc-fault simulator is shown in Fig 1(C). This simulator was designed based on standard UL1699B [19]. With the proper terminal voltage and electrode gap, the arc could be generated between a couple of coaxial copper electrodes A (Anode) and B (Cathode), which were mounted in insulation bases respectively. The discharge tips of electrode A and B are designed to be cone shape and flat shape respectively in the tests. Considering the electrode gap should be adjustable, the insulation base of electrode A was fixed on a steel sliding block, which could only make a one dimensional movement along the direction parallel to the two electrodes. The movement velocity and distance of electrode A from B, i.e., the length of electrode gap (or arc gap when discharging) L, was controlled by a programmable stepping motor, which could lead the sliding block move forward or backward precisely according to a screw structure rod. Also, there is another way to give a fine tuning to the gap L by hand using the distance control knob behind the stepping motor.

For a better observation of the arc with small scale, a high magnification digital camera (TD-208A from Taida Instruments, China) with 30 frames per second and maximum magnification rate 620 was set right above the electrode gap to record the arc shape from top view. Another use of this camera was to confirm or assist correcting the gap distance controlled by the stepping motor. A high speed camera (Phantom Miro M110 from Vision Research, America) with maximum 1630 frames per second was used to monitor the arc burning behavior from side view. As shown in Fig 2, temperatures were measured by thermocouple array (T1-T8) with each diameter 0.5 mm and uncertainty within 0.75%. T1-T4 were fixed on the surface of electrode A, which showed the surface temperature with position S (distance from the tip of electrode A) 1 cm, 2.5 cm, 4.5 cm and 6.5 cm. T5-T8 showed the ambient air temperature rises by arc heating with position S’ (distance from the edge of electrode B) 1mm, 1cm, 2cm and 3cm, respectively. Any trade name mentioned above is only for descriptive purpose.