Test circuit for evaluation of physical characteristics of SPDs with combined DC and impulse load

The rising amount of self sufficient DC systems for generating, storing, distributing and using electrical energy requires new surge protective devices due to the requirements arising from direct-current application. The development of such new devices demands commonly applicable and reproducible surge and line follow current pulses to reproduce typical fault current situations and to evaluate voltage and current limiting capabilities. In this paper, we present a test circuit for 10/350 μs lightning current with a possible superposition of line follow high-voltage direct-current. For this, we utilize an existing lightning current test system and present necessary modifications to create a line-pulser pulse forming network (PFN). With this, we are able to provide pulses of direct-current up to 1.2 kA at test voltages up to 6 kV with a pulse duration in the range of 2 ms to 25 ms. Furthermore, a combination of PFN und lightning current discharge is possible and presented here. With this new type of stress test, we first evaluated selected up to date spark gap-based lightning current arresters in terms of their direct-current limiting capability and current handling for combined direct-current and lightning current wave shapes. The results show a significant influence of the direct-current level and lightning current amplitude on the current limiting and interruption characteristics.