Study of arcing processes in circuit breakers by means of spatially resolved magnetic field recordings

Magnetic field measurements performed on a circuit breaker in order to study the switching arc processes are presented. Characteristic for these measurements is the spatial two-dimensional recording of the magnetic field with simultaneous high temporal resolution. A sensor head was developed for this purpose, which records the magnetic flux density in an area of 42 mm x 60 mm with a spatial resolution of 12 x 24 measuring points. A highly integrated sensor chip based on the Hall effect was used for the design. The configurability of this sensor chip makes it possible to adapt the time resolution to the measurement task, always in compromise with the amplitude resolution and the number of field components to be measured. Measurements with a sampling rate of 80 kHz were conducted. Also, with the sampling rate reduced to 25 kHz, three axis measurements could be performed. By combining two sensor heads into one measuring system, it was possible to perform simultaneous measurements at the two contacts of a low-voltage circuit breaker with double breaker. As a result, both slow and fast changes in the magnetic field caused by the arcing process were recorded and visualized. The changes in the field distribution measured with the two sensor heads correlated well with the respective arc voltage. With the help of such magnetic field measurements, study of the arcing processes in low-voltage switchgear should be made possible without interference of the arc itself.