Research Of The Effect Of Magnetic Field On Vacuum Arc Plasma Characteristics

With the rapid development of high voltage (HV) AC/DC power transmission and newenergy, the switchgear as the important core components in the AC/DC power system the basicfunction is to close and open circuit and change the connection mode and topological structureof the system, has the dual task of control and protection. Vacuum switch has the advantage oflow pollution and considerable development prospect compared to the other switchgears，which is widely used in centrally installed switchgear(CIS) and the distribution system and hasthe dominant position in medium voltage level of the power system. Research of the insulationand interrupting performance of the vacuum switches is necessary that has become one ofresearch focuses in the industry.When the vacuum circuit breaker (VCB) is opened, the arc will be generated between thecontacts. It will burn the contacts, destroy the insulation and delay the breaking of the circuit.Therefore, research of the vacuum arc is one of key problems to the R&D of the highertechnical parameter and larger capacity CBs. In this thesis, the VCB arc is taken as theresearch object, using finite element method (FEM) to analyze the vacuum arc characteristics,designed to support the application of vacuum switch in the field of DC open circuit.Because of the DC arc has no natural current zero point, compared to the AC arc, it ismore difficult to open. In this thesis, considering the influence of the classical diffusion, drift,electron impact ionization, excitation and so on, the fluid-chemical hybrid model of the arcplasma is presented. And the field-circuit coupling method is used to simulate the AC and theDC vacuum arc transient characteristics. The results show that under the same arc current, theAC arc plasma parameters distributions and the corresponding DC arc plasma parametersdistributions are the same.The VCB contact structure covers axial magnetic and transverse magnetic contact.Different function ways of the magnetic field have different effect on the arc. In this thesis, theequivalent two-dimensional contact model is proposed. According to the numerical results ofthe AC and DC vacuum arc characteristics, the vacuum arc arcing characteristics under theinfluence of the axial magnetic field (AMF) and transverse magnetic field (TMF) aresimulated. The results show that under the condition of either DC or AC circuit, the AMFmakes the arc in diffusing state, the TMF makes the arc offset and helps to the movement of arc roots. The equivalent value of the AMF and the TMF respectively applied the contactsystem has the same influence on the AC and corresponding DC arc plasma parametersdistributions. And both the AMF and TMF will weaken the ionization of vacuum arc.