Contents I. Introduction
For the optimization of low-voltage switchgear, the movement of the contact piece and the movement of the switching arc during switching are of central importance. A commonly used method for arc diagnosis is based on optical observation. Optical observation of the arc leads to the need of vastly modified laboratory sample gear. With such a modified device, influences on the switching behavior and especially on the movement of the arc cannot be prevented. To prevent the need for the use of modified devices, a diagnosis approach, which is only being used rudimentarily at the moment [1], based on the magnetic field, which is going to be introduced in this paper, is being developed. The approach is to measure and record the magnetic field outside of the breaking chamber on the exterior wall of the switching device during switching and to obtain information about the arc and contact piece movement by inverse calculation of the current density from the measured field. For this purpose, a high speed and high resolution magnetic field sensor array and the corresponding algorithms have to be developed to reconstruct the transient current paths [2]. While most of the recent development is for inspection of permanent magnets and non-destructive evaluation [3]–[5] work on current detection in various fields [6] [7] has also been published. But, little or no recent work is reported on magnetic diagnosis of switching technology.
