Risk assessment of surge current generated by spark discharges on open contacts of small power relays

Abstract

In this study, the spark discharge risks on small relays in low-voltage circuits are evaluated based on the test current magnitude and the rate of current change of surge current. For the risk assessment of spark discharge caused by the high-voltage switching surge on the small relay in low-voltage circuits, there are fewer papers relevant to the topic. First of all, this study presents the construction of a test circuit model, in which the open contacts of small relays are energised by a set of spark discharge generators. The actual current waveforms are measured and analysed. This study provides a manner to evaluate the risk degree of the small relay in low-voltage circuits damaged by the surge current. Referring to the relevant IEEE standards concerning surge protection, a surge protection circuit of a signal line is applied. The test is done after installing this surge protection circuit, the test of spark discharge is done after installing this surge protection circuit, and the test result confirms that the use of surge protection devices can suppress the surge current, so this study can be applied to reduce the hazards of the low-voltage equipment.