Applied Mechanics and Materials Vols. 303-306

Abstract: Some techniques of controlling remotely the digital storage oscilloscope are proposed including VISA, VXIplug&play drivers, TVC and IVI-COM drivers. By means of TekVISA, several application development environments can be used to develop functions of the digital storage oscilloscope. The programming language of Visual C++ is used to develop software. With the help of TekVISA and the dynamic link library, remote control to the digital storage oscilloscope through network is completed. All operations to the digital storage oscilloscope including parameters setup, data acquisition, waveform acquisition and storage, data processing are implemented in a remote place. The results show that the techniques of remote control are convenient and efficient and fit for experiments of scientific research and practical projects.

Abstract: To suppress the interference of radiated noise from the other ship and improve the measurement efficiency, a new method of the measurement for the ship noise with a single vector sensor was proposed. The ship at different direction were classified via the DOA estimation with a single vector sensor, then the radiated noise from the special ship was accumulated. The experiment of measuring the ship noise with a single vector sensor was conducted in the Yellow sea of China in the summer of 2010. The results showed the validity of the given method.

Abstract: Aiming to obtain higher navigation precision, this paper studied error sources of the acoustic Doppler Velocity Log (DVL) navigation system. Through analyzing the basic navigation equations of DVL, we knew that the acoustic navigating error was related to on-board attitude sensor error, velocity error and installation deviation error (array deviation angle and array eccentricity error). The author also derived the equations of random navigating errors and measure value errors, giving quantitative analysis of navigation error. Simulation shows the velocity error has more influence on the acoustic navigation error than others. The navigating precision can be promoted by increasing DVL precision, choosing high-precision attitude sensor and better installation error calibrating for acoustic array.

Abstract: IACC is an important objective acoustics parameter for evaluating hall acoustics. In order to find out subjective preference value or range of IACC for Chinese national music, under Ando’s hall acoustics theory, by keeping other acoustics parameters unchanged, subjective preference test on IACC was completed by paired-comparison method using headphone reproduction. Firstly, depending on measured binaural impulse responses with very low IACC, by adjusting correlation coefficient, five pairs of binaural impulse responses with different and equal-spaced IACC were derived and then convolved with CD musics including solo and tutti played by Chinese national musical instruments, thus auralization binaural signals were produced. The test’s results indicate that when IACC is between 0.15 and 0.41,acoustics for Chinese national music hall is preferable subjectively，accordingly, subjective preference range for IACCE3 is between 0.19 and 0.46.

Abstract: On-line insulation monitoring of transformer and the fault diagnosis are effective means to avoid sudden accidents happening on the transformer, which are necessary to perform the condition based maintenance (CBM) of transformer. Partial discharge is often accompanied by the external signals of sound, light and electricity as well as some detectable physical phenomena such as characteristic gas and dielectric loss. The partial discharge defects inside the transformer can be found by detecting the external signals. The principle of electro-acoustic monitoring, its monitoring systems and the related judgment technologies are expounded, on the basis of which an outline design of the monitoring system is presented.

Abstract: In transmission network, according to that current in each no-fault line connecting to same bus bar is so far less than current in fault line and CT isn’t saturated or a little, a method of acquiring current in fault line based on principle of continuity for electric current is proposed. It acquires current in fault line through measuring currents in no-fault lines connecting to the same bus bar, even considering influence from distributed capacitance of bus bar in time domain analysis. Simulations indicate that the method is correct, and can eliminate or effectively diminish influence from CT saturation.

Abstract: To evaluate the uncertainty caused by mismatch using Equivalent Capacitance Substitution Method (ECSM) with a T-network of matching resistors for monopole antenna calibration poses a problem. This paper derives the mathematical model of the mismatch factor through network analysis. The model can be used to evaluate the uncertainty component caused by mismatch or to calculate the mismatch correction factor using ECSM with a T-network for monopole antenna calibration. A case study on the application of the model to actual measurements is also included.

Abstract: Partial discharge will cause deterioration of insulation of high-voltage electrical equipment, resulting in insulation breakdown and short circuit accident. In order to ensure the normal operation of the high-voltage equipment, it is necessary to detect partial discharge online. By using Ultra High Frequency (UHF) defection method, statistical 2-dimensional (2D) patterns of partial discharge are obtained. Extracting the envelopes of the 2D patterns, we do the harmonic analysis for patterns’ envelopes, and the harmonic components are used as a characteristic parameter for defect type’s recognition. The results show that the harmonic components can be used as characteristic parameter for defect types’ recognition. This method has the characteristics of strong real-time and simple operation.

Abstract: Based on the basic theory of electromagnetic field, the Electric Field Distortion (EFD) in power frequency electric field caused by induced current of human body has been analyzed. The enhancement factor of the electric field distortion is introduced to reduce the influences caused by human body in the measurement of high voltage electric fields. The Ansoft Maxwell is used to simulate and calculate the electric field distribution under the influence of the human body to have the value of enhancement factor. In addition, the enhancement factor has been corrected by experiment with the electromagnetic field analyzer EFA300. With the enhancement factor introduced in this paper, the measurement error can be reduced.

Abstract: Because CNC systems are usually used in industrial sites, their immunity measurements are very important, this paper introduced how to perform the measurement of electrostatic discharge immunity, surge immunity, electrical fast transient burst immunity and voltage dips and short interruptions immunity. According to experience, it is not so easy to pass the measurements, this paper detailed suitable devices or other countermeasures to solve the problems in order to pass the four measurement items mentioned above.