Lin Xin

Magnetic field calculation and dynamic behavior analyses of the permanent magnetic actuator

Due to its great advantages, the permanent magnetic actuator for a vacuum circuit breaker drew great attention from engineers all over the world. We present the magnetic field and dynamic behavior analyses for the permanent magnetic actuator using finite element method associated with parametrization, for calculating the displacement of the moving parts and the supply current when the actuator is DC voltage supplied or capacitor supplied. In this analysis, the magnetic, electric and mechanical phenomena are coupled and some curves reflecting the dynamic behavior obtained. In addition, the comparison of dynamic behavior between DC voltage supplied and capacitor discharge supplied is drawm.

Calculation and analysis for line losses in distribution networks

The paper presents an improved backward-forward sweep method for solving radial distribution networks. The radial feature of the network has been fully exploited to develop an algorithm by a particular lateral, node and branch numbering scheme. The method has been extended for meshed distribution networks, using a multi-port compensation technique. The proposed method has been successfully applied to the solution of a number of practical distribution networks.

Motion control system simulation of cylindrical linear induction motor used in circuit breaker operating mechanism

According to the requirements of movement characteristics during the opening and closing of 40.5 kV vacuum circuit breaker on operating mechanism, this paper designed a new type of motor drive operating mechanism-cylinder linear induction motor (C-LIM) drive mechanism. Based on the characteristics of short trip, strong anti-force, high speed in mechanism, analysis the motor mechanism movement characteristics, calculated the dynamic characteristics of the contact under the optimized velocity curve and also plan the move curve of the contact in the paper. Pointing at proper border effect of C-LIM mathematical model is built of vector control system when consider dynamic vertical border effect, and simulated of the mechanism control system for driven by (C-LIM) in MATLAB environment. The simulation results show that it can get a good dynamic performance, small vibration and perfectly meet the requirements of mechanism movement characteristics during the opening and closing of circuit breaker when the linear motor direct drive circuit breaker actuator operating shaft, and still lay the foundations of circuit breaker intelligence control.

Theoretical analysis of mechanical characteristics of vacuum circuit breaker with spring operating mechanism

In this paper, mechanical characteristics of spring operating mechanism of vacuum circuit breaker are calculated theoretically and the normal opening speed curve is obtained when spring mechanism is operated under unload condition. The calculated results have good coincidence with the real testing results. And at the same time, the fault opening speed curves are also calculated assuming that some components of the spring operating mechanism are in fault conditions. The calculated results are valuable for the circuit breakers on-line monitoring, fault diagnosis and condition maintenance.

Design and dynamic simulation of permanent magnet motor actuator on high voltage circuit breaker

A novel permanent magnet motor actuator on high voltage circuit breaker is proposed. Based on the characteristics requirement of the circuit breaker, a limited angle permanent magnet brushless DC servo motor actuator is designed. By using the finite element method, the basic characteristics and dynamic simulation of starting are carried out, which the simulation results of the motor (such as electromagnetic torque, current, speed and location parameters) have been analyzed. The analysis is indicated that the rotary motor actuator can provide the mechanism characteristics and so it can supply a basis for vacuum circuit breaker using the rotary motor actuator.

Effects of Series Reactor on Short-circuit Current and Transient Recovery Voltage

With the increasing of short-circuit current of the power grid, by use of series reactor to limit 500 kV short-circuit current is feasible, but the introduction of series reactor could change the transient recovery voltage and have effect on the circuit breakers interrupting performance. In this paper, 500 kV reactor is used to limit short-circuit current of Dongqing substation, the current changes of different reactor values under three-phase short-circuit fault are analyzed, the best-value work interval is obtained; at the same time, the problem of TRV is solved by the mean of introduction parallel capacitance, it can reduce the amplitude and rate of TRV. The results showed that: the way of using parallel capacitors to reduce amplitude and rate of TRV is feasible, if reduce the amplitude of the TRV substantially, larger capacitors are required.

The Analysis of Secondary Arc Extinction Characteristics on UHV Transmission Lines

One of the important operational conditions of a single-circuit transmission line is the reclosing of circuit breaker, which depends on the value of secondary arc current. This paper presents the major methods of suppressing secondary arc current in ultra-high-voltage power transmission system. When the high speed earthing switch is adopted, the effect of secondary arc is studied. The magnitude of the secondary arc current and recovery voltage in arc path are obviously reduced after installing high speed earthing switch on line, which in turn reduces the extinction time of the secondary arc and assures successful single-phase auto reclosure. The arc affects the single-phase reclosing time of an ultra-high-voltage power transmission line, which is investigated on the basis of the secondary arc models.

Notice of Retraction A Novel Power Predicting Model of Wind Farm Based on Double ANNs

To solve the problem of the variancy of the wind power when wind farm connect with the power grid, a wind power predicting model of wind farm based on double ANNs is proposed in the paper. Wind velocity and wind direction on wind farm are the key of wind power predicting, and other circumstance conditions such as temperature, humidity, atmospheric pressure, are also great influence on it. The observed values of these five circumstance conditions can be treated as a nonlinear time series and be analyzed by the nonlinear time series ANNs model. The wind power predicting model consists of double artificial neural networks. The first is consisted of five artificial neural networks which is used to prediction the circumstance conditions time series, the second is employed to prediction the power of wind farm use predicting value of the five conditions. A series of simulation show that the results of the predicting model is acceptable in engineering application.

High frequency model of metal-oxide surge arrester for researching on VFTO

In the simulation of very fast transient over-voltage (VFTO), establishing the accurate equivalent model of electrical equipments in GIS has a major effect on the calculation results. At present, nonlinear resistance model based on static V-I characteristics is used for metal-oxide surge arrester (MOA) when simulating the VFTO in GIS. But the result is not accurately, because polarization in high frequency electric field is neglected by this model. In this paper, combined with the conductive process of grain and grain boundary in the microstructure of arrester valve piece, based on the polarization theory in alternating electric field, the high frequency circuit model of arrester is proposed, and the model can accurately simulate polarization process of arrester in high frequency electric field by comparing the simulation and the actual waveform. Then based on a GIS in China, the VFTO is simulated with the high frequency model, and the effect of MOA on VFTO amplitude, spectrum characteristics and gradient are analyzed. The simulation results show that, MOA has some inhibitory effect on the amplitude and steepness of VFTO, especially for the equipments that nearing the arrester. In addition, the nearer equipment from the arcing disconnector, the greater steepness on it, conversely, the farther from the disconnector, the steepness is lower. The result has some practical significance for calculating and analyzing VFTO.

Comparison and Analysis on Very Fast Transient Overvoltage Based on 550kV GIS and 800kV GIS

The transitional process from EHV to UHV not only brings many technical problems, such as zero drift, resonance overvoltage, quenching of secondary arc current, but also makes the problem of VFTO in GIS caused by operating disconnector increasingly outstanding. With the development of UHV GIS in China, there still exist many works to be done thoroughly for the further study of VFTO characteristics. In this paper, a mathematical model has been set up respectively based on a 500 kV GIS and an 800 kV GIS to study the amplitude-frequency of VFTO and its effects on power transformers, using FORTRAN and EMTP. The protective effect of shunt resistor of DS has been verified again in suppression of VFTO in 800 kV GIS. By comparing and analyzing the calculation results between the two EHV systems, an important reference is provided to accelerate the UHV transmission network for the localization of UHV utilities and GIS manufacture.