Interruption of Medium-Voltage Direct-Currents by Seperation of Contact Elements in Mineral Oil Using an Ultra Fast Electro-Magnetic Actuator

Abstract

The increasing usage of medium-voltage direct-current in upcoming electrical energy grid topologies requests novel solutions for MVDC switching. The interruption of direct-currents is accomplished by enforcing a current zero crossing by adequate means and preventing reignition due to the recovering dc voltage. This paper evaluates the rapid separation of the contact elements in mineral oil leading to a liquid flow around the contact elements and the switching arc. The energy turnover of dielectric liquids interacting with an electric arc is considerably higher leading to heavily increased arc voltages compared to dielectric gases. This paper confirms results of earlier publications and carries them further towards a possible usage in an MVDC switching or protection device. Thus a contact arrangement surrounded by mineral oil in combination with an ultra fast electro-magnetic actuator is introduced and performed measurements are discussed.

Experimental study on the underwater DC arc behaviors regulated by an external transverse magnetic field

“…Furthermore, the random moving arc in water without control is difficult to apply to DC fault current protection. Some methods prove to be effective for directionally driving the arc, such as adopting electrodes with an arc running angle [12], forced liquid flow [13] and fast opening of electrodes using a repulsion mechanism [14]. In addition, arc control can also be achieved by applying an external transverse magnetic field (ETMF), which has been rarely reported in water.…”