Zenghui Lai

Arc fault diagnosis and analysis based on wavelet neural network

Research on the external characteristic of the switch with contact is an important subject in breaking techniques nowadays. In this paper, based on the proposed experimental platform covering the arc fault diagnosis, load selection and wavelet neural network (WNN) design, a combination method of the experiment and simulation of the actual lines for the arc fault testing system is presented. And the external parameters of the series arc fault has been obtained under different loads, such as the resistance-reluctance loads and a series of electrical loads. By using the wavelet packet transform, frequency bands subdivision of experiment data and energy statistics under different frequency band are accomplished. And the current energy distributions for different loads under fault condition have been obtained and figured out. Additionally, the proposed energy criterion is applied as the input and the trained relax-model WNN can identify the arc fault effectively. By analyzing the arc faults of different loads for the demonstrated cases, the feasibility and the validity of the proposed scheme for arc fault diagnosis is verified.

Research on insulation characteristics of multi-break in series extra high voltage vacuum circuit breaker

Multi-break in series is the measurement applied in the design of the extra high voltage vacuum circuit breakers (EHV VCBs). Because of the existence of the coupling and transient variation of the multi-physical fields, the multi-break in series is the uniformed large space-time field system covering the multiple physical parameters. And the insulation performance for each break in the series system change a lot than one break case, and the investigations on the unknown factors are necessary. Based on the application of the EHV VCB applied in the system, the dynamic insulation coordination property covers the dynamic insulation of each break and the design of the multi-break in series. In this paper, the 3D electric field of the triple-break vacuum interrupter (VI) in series is numerically simulated using finite element method (FEM). And the location of the maximum electric field strength and the field distribution along the surface of the movable and fixed contact are calculated and figured out. By the comparative analyses with different insulation structures in series, the variations of the electric field strength are obtained and illustrated. Moreover, by introducing the shielding covers and parallel capacitors, the design of each 72.5 VI unit is accomplished and the insulation property of the 220kV triple-break in series EHV VCB is analyzed.