Chunguang Hou

Design and Analyses on Permanent Magnet Actuator for Mining Vacuum Circuit Breaker

A novel permanent magnet actuator (PMA) for mining vacuum circuit breaker (VCB) is presented in this paper. Which is monostable, has two coils and able to break the VCB when the fault of low-voltage happened. And can detect the voltage variation in main circuit at each instant. When the fault of low-voltage happened, it can automatically break without additional detection and control of apparatus. Moreover, the different states and parameters of breaking and closing courses have been numerical computed and analyzed by adopting ANSOFT software. Based on the simulation results, the prototype is manufactured and assembled in the mining VCB. The feasibility and validity of the proposed PMA have been proved by testing results

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.

Flow rate measurement system using thermal air flow sensor

An intelligent digital flow rate measurement system is presented to replace the conventional hot-wire flow rate measurement system, which uses original analog feedback circuit. In this paper, the conventional Wheatstone bridge measurement circuit is replaced by a new Pulse Width Modulation (PWM) circuit for the purpose of energy conservation. The system employs a PIC18F452 chip to interface a thermal flow measurement system to measure the flow rate. And a signal prediction algorithm is introduced to speed up the measurement. It has been proved that the performance of the intelligent digital flow rate measurement system has been increased compared with conventional flow rate measurement system based on the thermal air flow sensor.

Design and stationary characteristic analysis of magnetic system of small capacity permanent magnet DC contactor

Permanent magnet DC contactor has the advantages of simple structure, low energy consumption and low noise. A magnetic system structure applicable to DC contactor is presented in this paper. Based on the traditional structure of single coil and single stable position contactor, an auxiliary gas gap is added. By changing the size of the gas gap to change the attraction of permanent magnet, the whole magnetic system improves the reliability of breaking-closing operating. A mathematical model of the magnetic system is established, and the magnetic field and the stationary characteristic are calculated by using finite element method. According to the calculations, cooperation between attraction characteristics and counterforce characteristics is analyzed and the result indicates that the magnetic system, which has a advantages of strong electromagnetic actuation, reliable breaking, manual resetting without disassembly, can be used in industrial production.

PIC simulation of discharge in vacuum and influencing factors

There are great differences between vacuum discharge and common gas discharge. For short gap gas breakdown, the main reason can be explained as followings: electrons from the cathode emission are accelerated by the electric field and impact the anode which will release a lot of metal vapor. The ions produced by the collisions between metal vapor gas molecule and electron impact the cathode and secondary electrons emission will come into being. Based on the field emission theory in vacuum, particle in cell simulation method is used in our paper to trace the motion of electrons produced by cathode emission and ion produced by collision in time and space dimensions. Mont Carlo method is used here to cope with the collisions between electrons and neutral molecules. The cross sections of the collision which relate with the energy are all from the experiments. The secondary electron emission, exciting, elastic and ionizing collisions between electrons and metallic vapor molecules have been considered in our paper. The state parameters of charged particles at any position and time are recorded and the effect of vacuum degree on discharge voltage are simulated which can explain the mechanism of vacuum discharge from microscopic view.

Arc igniting mechanism analysis of high voltage interrupter based on PIC-MCC method

In order to explain the mechanism of high voltage interrupter, a particle in cell method is used in our work to simulate the breakdown process before arc formation of vacuum and SF6 circuit breaker. The electrons and ions which play vital roles in this process are traced by Newton equation. The electrons from field emission, impact ionization and secondary electron emission are all considered in our simulation. The effect of space charge on the motion of charged particles is considered here. Constant time step method of Monte Carlo is used to cope with the collisions between the particles. For vacuum breaker, the exciting, elastic and ionizing collisions between electrons and metallic vapor atoms have been considered here and for SF6, momentum transfer, excitation, dissociative ionization and attachment are considered. The simulation results explore the breaking mechanisms of different circuit breaker and have some values on arc quenching research.

Simulation on SF 6 gas discharge by PIC-MCC method

Sulfur hexafluoride is a gas with high electronegativity. For its strong adsorption to the electrons, it is widely used in the gas insulation. A microscopic model is established in our work to study the motions of particles in sulfur hexafluoride gas. Particle in cell method is used to trace the motions of the charged particles and the collisions between electrons, ions and atoms are simulated by a random method - Monte Carlo collision method. A plane electrodes system is modeled in our work and the distance between the electrodes is 25.4mm and the voltage between the electrodes is 12kV. The temperature of the gas is 293K. We traced the motions of a large amount of the electrons and assembled average which made us acquire the macroscopic distributions. Nine types of collisions between electron and molecule are considered in our work and the elastic collision and charge exchange between ions and atoms are also considered. According to the simulation, the densities of different particles and the electric field solved by Possion equation are acquired.

Research on rotary-gas high voltage SF 6 circuit breaker with novel blade nozzle Part I: Design and research on novel blade nozzle

In order to improve the dielectric recovery characteristic in high voltage circuit breaker (HVCB), the method of rotating gas flow to extinguish the arc is presented in the studying of a 126kV single-break SF6 CB. And a novel arc quenching chamber structure with blade nozzle is presented and three dimension (3-D) mathematical model of arc quenching chamber in SF6 CB is proposed. The Finite Volume Method (FVM) and total variation diminishing (TVD) schemes are used to numerically calculate the gas flow model. The characteristics of cold gas flow in arc quenching chamber during the interruption for different structures are simulated. The distributions and variations of gas flow field quantities in the arc quenching chamber such as velocity, pressure and density have been obtained and compared. The feasibility and validity of the proposed blade novel nozzle structure has been proved.

Measurement of arc temperature in SF 6 model circuit breaker based on CCD

Investigation on arc shape in SF6 circuit breaker has very important significance to analyze arcs forming, moving and extinct principles, to reduce its dimensions and enhance switching capability. In order to facilitate to research arc characteristics, a set of dismountable SF6 model circuit breaker is designed in this paper. The experimental system of diagnosing arc plasma parameters is built based on Charged Coupled Device (CCD) signals. Finally, the temperature distributions of arcs plasma are obtained through Abel inverse transformation.

Simulation on the formation of sheath in argon discharge

The formation of arc in high voltage equipment is an unbalanced gas disruption and the principles of it are important in apparatus switching. For the complexity of gas disruption principles, the modeling and computer simulations to the beginning of gas disruption are vital in this domain. Particle-in-cell method is adopted in our work to disperse the Boltzmann equation and build a mathematical model. The gas disruption between the contacts of electrical apparatus at the beginning of switching is studied by this method and the microscopic parameters about gas disruption and the formation of sheath are also acquired here. A lot of charged particles are traced in our work and the formation of plasma sheath, the distribution function of electron, ionization rate, density of electron and the electric field are acquired. The long-range collisions between electron, ion and atom are considered here and the cross section is relating to particle energy. It can be seen from the results that the voltage between the electrodes have an effect on the formation of the sheath and the sheath plays an important role in breaker switching.