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The residual axial magnetic field (AMF) at current zero, which is caused by large di/dt during the forced current-zero stage of DC interruption based on the technique of artificial current zero, has significant influence on the interruption performance of the vacuum circuit breaker. In this paper, a model of AMF contacts is developed by finite-element-analysis software, Ansys. The eddy current induced...
In this paper, the temperature rise situation under normal operation of a 12kV medium voltage switchgear is studied through modeling and simulation method. Firstly, in the simulation analysis of the whole switchgear, based on the theory of eddy current field, gas flow field, and temperature field, the temperature rise distribution of the switchgear under the condition of natural convection and forced...
Wire explosion technique has been widely studied in recent years to produce nanoparticles of different materials due to the enormous outstanding characteristics of nanomaterials as well as the advantages of wire explosion technique1. In the wire explosion process for preparation of nanoparticles, the wire firstly melts, vaporizes and then generates a mixture of metal vapor and liquid droplets. The...
A series of triggering experiments were carried out to investigate into the characteristics of vacuum arc controlled by TMF-AMF contacts. During the whole experiments, current ranged from 5kA to 20kA (rms) and both arc appearance and the behavior of cathode spots were captured by high-speed camera with corresponding arc current and arc voltage. A 3D steady MHD model was built to simulate and analyze...
Microsecond explosion of metallic wires has drawn attention of many researchers due to its complicated physical process and various applications, such as production of metal nanoparticles1. When a high density pulsed current passes through a thin wire, it quickly melts, vaporizes and ionizes. The medium pressure and charging voltage have significant effect on the development of the generated plasma2...
The fast electrical explosion of a metal wire is a common method to study the behavior of wires during the prepulse in wire array Z-pinch. The experimental results of the electrical explosion of aluminum (Al) wires using negative nanosecond-pulsed current with magnitude of 1∼2 kA are presented in this paper. The Al wires with different diameter are exploded with current rate of 90–170 A/ns. A laser...
In this paper, a method is proposed to simulate the two-dimensional random motion of a single cathode spot step by step. Simulation parameters, e.g., the characteristic displacement and time step of random motion, are taken from relevant experimental data. In every motion step, the moving direction along the x axis (+x or −x) and y axis (+y or −y) are chose randomly, and the displacements along the...
The 300MW turbine generator which uses Tung oil-BMI-epoxy resin-rich insulation in Wu Jing Thermal Power Plant was subjected to a wide variety of diagnostic tests during the regular planned overhaul. This generator has kept safely running for 23 years since 1991. Diagnostic tests included direct current diagnostic tests, capacitance, dissipation factor and tip-up, partial discharge, AC proof voltage...
In this paper, a non-destructive method based on isothermal relaxation current (IRC) theory was used to diagnose the insulation condition of stator bar specimens during thermocycling aging. One thermocycling aging cycle is “room temperature-160 °C — room temperature”. In test cycle, five specimens were taken out to do insulation puncture test except IRC test. IRC test includes three steps, i.e. polarization,...
The influence of lagged axial magnetic field (AMF) due to eddy current induced in contacts system on the distribution of cathode spots (CSs) in current-zero stage of vacuum arc with different current falling rates was investigated experimentally. Experiments were conducted with cup-shaped AMF contacts in a demountable vacuum chamber. The characteristic of CSs distribution of triggered vacuum arc in...
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