Liao Ruijin

Numerical simulation and experimental validation of a direct current air corona discharge under atmospheric pressure

Air corona discharge is one of the critical problems associated with high-voltage equipment. Investigating the corona mechanism plays a key role in enhancing the electrical insulation performance. An improved self-consistent multi-component two-dimensional plasma hybrid model is presented for the simulation of a direct current atmospheric pressure corona discharge in air. The model is based on plasma hydrodynamic and chemical models, and includes 12 species and 26 reactions. In addition, the photoionization effect is introduced into the model. The simulation on a bar-plate electrode configuration with an inter-electrode gap of 5.0 mm is carried out. The discharge voltage—current characteristics and the current density distribution predicted by the hybrid model agree with the experimental measurements. In addition, the dynamics of volume charged species generation, discharge current waveform, current density distribution at an electrode, charge density, electron temperature, and electric field variations are investigated in detail based on the model. The results indicate that the model can contribute valuable insights into the physics of an air plasma discharge.

The harmonic analysis method and its application in the on-line detection of electric equipment insulation

This paper describes the harmonic analysis method which can be used to measure the resistance current of the metal oxide arrester (MOA) and the dielectric loss of the capacitive apparatus. The theory of this method and the requirement to the hardware circuit are introduced also. The testing and the analysis of the theory show that this method is more accurate and sensitive than the routine compensation method for measuring higher order harmonic of the resistance current, and it can improve the stability and the precision for measuring tg/spl delta/. At last, the actual measuring results of using this method in substation are given also.

Experimental study on irreversible electrical breakdown of tumor cell under steep pulsed electric fields

Describes the dynamic changes of the SKOV3 cancer cell under steep pulsed electric fields (SPEFs, generated by the energy-controllable steep pulse apparatus for tumor treatment) using an inverted phase contrast microscope (IPCM) and finds that the cell was swollen in very short time. The study showed that the membrane of treated cell was destroyed under a scanning electron microscope (SEM), the nucleus was swollen and its karyotheca was not integrated under the transmission electron microscope (TEM). The mitochondria was also cavitated and swollen. It is clear that the SPEFs can result in irreversible electrical breakdown of the tumor cell. It may be a new therapy for tumor treatment.

GIS based distribution system spatial load forecasting and the optimal planning of substation location and capacity

The geographic information systems (GIS) platform is used in spatial load forecasting (SLF) and the mathematical models of the substation location and capacity optimisation problems are established in this paper. Based on the theory of network flow, a new multi-period optimal selecting algorithm of substation is proposed, which could determine the reasonable location, capacity and time that are put into the running of the substation. The real instance shows that this algorithm could solve the multi period optimal selecting problem of substations in distribution system planning (DSP) successfully, and has a practical value.

A steam turbine-generator vibration fault diagnosis method based on rough set

According to turbine-generator vibration characteristic spectrum, a discretized generator fault attribute decision table and condition. attribute set reduction method based on rough set theory are presented in this paper, though the key character which influences classifying is picked up. BP network input dimension is reduced and training time is saved. Experiment shows that the result is effective.

Study on calculation model of the lightning protection performance of shielding failure for 500 kV double circuit transmission line

Using double-circuit transmission line is the developing trend for 500 kV main configuration to reduce the line holding ground, So analyzing its lightning protection performance is significative to extend double-circuit transmission line in Ultra high voltage network. When analyzing the lightning protection performance of shielding failure for 500 kV double-circuit transmission line, the EGM is improved by considering the effect of wind speed and the calculation model is built in this paper. Furthermore, the results that more accord with the practical condition are got by using program to calculate it.

Time domain electrical impedance measurement method for ultrasound transducer

High intensity focused ultrasound transducer (HIFU) is a key part of HIFU treatment system, the electrical impedance characteristics of which is an important parameter. The currently adopted electrical impedance measurement methods are based on frequency-domain, which are expensive and difficult to realize on-line measurement. The time-domain measurement method for electrical impedance of high intensity focused ultrasound transducer based on impulse response is studied in this paper. The principle of measurement is theoretically analyzed and verified through simulation. The measurement platform is experimentally established and the measurement results of impedance analyzer and impulse response method are compared. The approaches of current sampling resistor correction and wavelet denoising to reducing measurement error are presented. The study results show that: the impulse response measurement method can obtain good measurement accuracy after current sample resistance correcting and wavelet denoising; the measurement method is cost-effective and convenient for integrating in equipment to realize on-line measurement. This measurement method also provides an effective means of researching electrical impedance characteristic of high intensity focused ultrasound transducer.

A practical PD online monitoring system used for transformers

In this paper, we develop a partial discharge (PD) online monitoring system with frequency band from 50 kHz to 1 megahertz used for transformers. The monitoring system mainly consists of wide-band signal detectors for multi-terminal measurements, signal pre-processing circuit, high speed A/D converter and cascaded 2nd order IIR lattice digital notch filter. The major measures to suppress narrowband interference are the signal pre-processing device and the digital notch filter. With analysis to field monitored signal from a transformer at a 220 kV substation, it is shown that the monitoring system can detect and extract the discharge pulse signal effectively. With PD pattern recognition method, the monitoring system can get more stable and reliable detection results.

On-line detection of gases dissolved in transformer oil and the faults diagnosis

This paper describes the theory of on-line detection of six kinds of gases-H/sub 2/,CO,CH/sub 4/,C/sub 2/H/sub 4/,C/sub 2/H/sub 2/,C/sub 2/H/sub 6/-which are dissolved in transformer oil, and analyzes the characteristics of the microcomputer detection system. The back propagation neural network (BPNN) is applied to diagnosing the transformer faults, and the results of verification show that the BPNN diagnosis method is effective.

The development of the linear Rogowski coil for measuring large impulse current

This paper describes the theory, design of the linear Rogowski coil, and analyzes its properties. The testing results show that it can measure not only large impulse (or power-frequency) current but also distributing impulse current on tabulate conductor. The rise time of this coil is about several nanoseconds, and its structure is simple. So it can be well used.