Investigation of the Pinch Mechanism of Liquid Metal for the Current Limitation Application

Fault current limitation is a promising solution to protect power transmission lines and electrical apparatuses. A specially designed setup is employed to observe the pinch process of liquid metal for application of current limitation, which can be classified into three stages. The liquid metal first separates from the nonsmooth spacer channel’s surface to form a uniform air gap between them. Then, it keeps deforming as the air in the gap flows toward both ends of the channel. A moustache-shaped air cavity forms finally in the channel ends and enlarges continuously until arc ignition. Besides, the fluid pinch properties influenced by several parameters are investigated by experiments including the heights of the fluid free surface and the surface profile of the spacer’s channel. To reveal the pinch mechanism, a numerical model based on the volume of fluid method and magnetohydrodynamic theory is built finally and solved by the software FLUENT, which corresponds well with the test results. It is concluded that the formation of the moustache-shaped cavity to “cut off” the liquid metal in a liquid metal current limiter arises from several factors including the nonsmooth spacer channel’s surface, the unstable flow of galinstan, and its unique properties (considerable viscosity, surface tension, and oxidization).