Advanced Materials Research Vols. 960-961

Abstract: The model of electrolytic cleaning for cold rolled strip was established, and the simulation of cleaning process was carried out in the finite element method with the software (Ansoft). The influence of processing parameters was investigated. The results show that, the processing parameters, such as the current efficiency, the electrode plate intervals and the insulation board have intense influence on current efficiency, which is significant for improving cleaning efficiency and energy conservation.

Abstract: ZnMn ferrite, cold-rolled silicon steel, permalloy and nanocrystalline alloy can be used as magnetic cores of current sensors. And based on these four materials’ inherent characters of electromagnetic, this paper presents closed loop simulation model of them using Ansoft which is a finite element analysis software. In simulation, the measuring currents are set to DC currents ranging from 0 to 1mA. And different amplitudes of variation of currents are set for each material. The simulation of each material produces 280 sets of data and with these data a series of curves of magnetic field changing with currents can be plotted using Matlab. The simulation results show that permalloy and nanocrystalline alloy have good characters of electromagnetic and they are suitable for detecting weak DC currents. When these two materials are used as magnetic cores of sensors, the theoretical detecting accuracy can be up to 0.001mA, meanwhile, detecting accuracy of ZnMn ferrite is about 0.1mA to 0.01 mA.

Abstract: To make up insufficient of ESDD in insulator flashover voltage analysis, and A more comprehensive assessment of antifouling properties of insulators. This paper discusses the factors of suspension insulator flashover voltage of the AC, analyzed the influence of these factors on the flashover voltage, found the reason for large differences of the current test results of research institutions at home and abroad, and proposed future research directions.

Abstract: An application of intelligent pressure detection and alarm system are studied in this paper . it is consists of the high integration, powerful function new microprocessor control, the internal integration of a large number of analog and digital peripheral module. The system has strong data processing ability. multifunctional intelligent hardware is not only realized in circuit necessary configuration,but also is a small size device. it ensure the intelligence function,and has the advantages of small volume, low cost, integration and strong anti-interference ability .

Abstract: Commutation failure theory of HVDC system is proposed and its reason is analyzed. Faults at inverter bus in multi-infeed HVDC system can cause local commutation failure and even concurrent commutation failure. Anomalous commutation failure is simulated with six kinds of ac system strength, and it is more and more serious at first as the system strength increases then become less serious as the strength becomes stronger. Coupling impedance is changed to get its relationship with anomalous commutation failure.

Abstract: Commutation failure is one of the most common typical faults of HVDC, and it may result in subsequent commutation failures, even the outage of the HVDC system if without timely and effective regulatory measures. Trigger of the control measures depends on the rapid and accurate diagnosis of commutation failure. In-depth analysis of the commutation failure mechanism indicates its new substantive characteristics: valve voltage being continuously zero and valve current being continuous with high amplitudes, according to which a novel method for fault diagnosis of commutation failure based on voltage or current of the converter valve is proposed in this paper. Simulation results prove the accuracy and effectiveness of this method.

Abstract: Due to the high current density in 77K, the high temperature superconducting facilities are expected to improve the efficient in power transmission. Superconducting facilities electromagnetic design is highly dependent on the characteristic of the superconducting tape. As a result, the comparison of the effect of different tape in electromagnetic design should be studied. In this paper, several facilities model are used as example to analyze the effect of different tape utilization. The result shows in different application conditions, or, specific benefits are considered, there is a specific tape will be the best choice.

Abstract: This paper proposes a new method to evaluate the voltage sag sensitivity (VSS) of the sensitive load by the combination of several probability density function models, which can fully describe the randomness of load sensitivity. Firstly, five common probability density functions were respectively used to build the mathematical model of voltage tolerance curve (VTC) of sensitive load in uncertainty region. Secondly, the VSS of sensitive load was respectively evaluated by five models, and the weighted sum of five models’ results was calculated by unbiased variance method. In the end, the proposed method was verified to be rational according to an application example.

Abstract: When the single phase ground fault occurs in resonant grounded system, there are significant differences in the components of fault phase current between fault line and non-fault line. This feature can be reflected by intrinsic mode entropy (IMEn) of fault current. IMEn is a new signal analysis over multiple oscillation levels. It corresponds to the sample entropy (SampEn) and the empirical mode decomposition (EMD). The results of fault simulations in different conditions indicate that the method is reliable.

Abstract: Hilbert-Huang transforms calculation method was used in the study on signal of partial discharge from on-line cable. The partial discharge signal was made to be intrinsic mode function (IMF) by empirical mode decomposition (EMD).The cubic spline interpolation was selected as the interpolation function and ideal envelope curve was achieved to eliminates defects such as overshoot and undershoot effectively. Appropriate lock-in amplifier was choosed and pre-amplifier and phase sensitive detection circuit was designed to determine the calculation programs. The results showed that the test system can effectively capture the weak PD signals in cable under complex environmental conditions and the PD signal waveform obtained was improved through Hilbert-Huang transforms.The state of insulation and the remaining life of the cable can be judged effectively,which has practical significance for improving the grid security.