Artificial Low Current Arc Fault for Pattern Recognition in Low Voltage Switchgear

Low voltage switchgear is usually protected against over-current and short-circuit by fuses and circuit-breakers. However, protection devices are not sensitive enough to detect low current arc faults, which may arise for example by slow loosening of screw or rivet connections in an electrical busbar [11]. Here, the current is within the range of the rated current and limited by the connected load, known as serial arcs. Parallel low current arcs between two phases or phase and ground are also possible and may be initiated by contamination. Both types of failures result in a local heating-up of the busbar material and insulation material and can cause local carbonization and low current arcing. After a certain time this process can result in a short circuit and may damage the whole switchgear. To test the reliability of arc fault protection devices, usually an arc is generated by a short circuit between 2 or more phases. However, it is difficult to test other faults than a very low resistive short circuit with usually high arc current. In this paper, a method will be demonstrated and discussed, how to ignite an arc with a relatively low arc current which is burning for at least 80 ms. By using resistors to limit the arc current and due to special devices to ignite the arc, it is possible to generate arcs up to 1200 A peak to peak current in a very reliable, reproducible and save way. Using this method, arc fault detection devices, which are able to detect arc faults within the rated current range of the switchgear, can be tested.