Zhou Bihua

Experimental investigation of EMP shielding effectiveness of reinforced-concrete cell model

For studying the EMP shielding effectiveness, various shielding cell models are established, which are composed with mesh of reinforcement bars or reinforced-concrete. The results of experiments show that if the reinforcement mesh cells and reinforced-concrete shielding cells are specially designed, shielding effectiveness for an EMP plane wave can be about 40 dB and 20 dB for E-field and H-field respectively.

Analysis of transient grounding resistance under pulsed discharging current

This paper presents numerical analysis of the transient grounding resistance of the grounding conductor under pulsed discharging current using the FDTD method; and analyses the influence of its size, buried depth and the ground conductivity. In the end, methods for reducing transient grounding resistance and discharging faster are discussed.

Analysis and Test of EM Shielding for Low-Frequency Magnetic Field

Electromagnetic shielding is the technique that reduces and prevents coupling of undesired radiated electromagnetic energy into equipment, so as to enable it to operate compatibly in its electromagnetic environment. Usually, the frequency considered for electromagnetic shielding design is above 10 kHz, but the lower frequency for some special demand is 50 Hz or even 0.01 Hz sometimes. This paper mainly studies the shielding design for low-frequency magnetic field, and the shielding effectiveness of single shielding and multimedia shielding are discussed separately. Moreover, the shielding effectiveness of a steel shielding enclosure and two different shielding doors for low-frequency magnetic fields in the near zone is measured.

Full-waveform measuring system for lightning current caused by lightning strikes to tall structures

In order to protect electronic devices against the effects of lightning strikes to tall structures, detailed information about the lightning currents are necessary. For this purpose, a full-waveform measuring system was set up on the north towers of Jiangyin Highway Bridge. In this paper, the calibration to this system is introduced and the results of simulating lightning currents are given.

Application of MW-FDTD to simulate the electromagnetic pulse(EMP) propagation in tunnel

To simulate the EMP propagation in large-scale and long-distances vaulted tunnel, an effective MW-FDTD method based on parallel computing [1] was presented. The convolution PML (CPML) [2] is adopted to truncate the computation domain, which reduces the reflection error greatly. The accuracy and the efficiency of the proposed method have been verified by comparing the results of the parallel FDTD algorithm with the proposed method.

Statistical results on the emp conductive susceptibility of a serial network measurement and control device

The EMP conductive susceptibility of a measurement and control device used in automatic management system is studied by experimental test. Two EMP waveforms with different rise time are applied to the devices. Responses of the EUT are measured and compared. The sensitivity thresholds of EUT are analyzed by statistical method. Results show the EMP with fast leading edge tends to cause more serious interference when its amplitude remains the same as the EMP with slow leading edge.

Influences of mesh size and lightning channel length on lightning electromagnetic field calculation using FDTD algorithm

One of the most important problems of FDTD method used in calculation of lightning electromagnetic effects is that the calculation is very expensive, time consuming, and sometimes even impossible due to the computer limitations. Mesh size and lightning channel length can greatly affect calculation speed in lightning electromagnetic field calculation. In this paper, Influences of different mesh sizes and the lightning channel lengths on the calculation have been discussed. Very strait grid can be used in lightning electromagnetic field calculation without any scatter object; however, too strait grid will cause error when scatter object is taken into consideration. The proposed 7500m channel length is not necessary for lightning electromagnetic field in the vicinity of the channel. Shorter channel can be used to calculate the nearby lightning electromagnetic fields; closer the area we care about is, shorter the channel is necessary.

Research on Distribution of Electric Field near Ground during Thunderstorm Process

In this paper, electric field near ground during thunderstorm process is discussed with field data measured by thunderstorm electric field mill and numerical simulation. The measured field data shows that the atmospheric field became strong as measure height increased. The cause is given out by the numerical simulation. And the result of numerical simulation shows accordance with measured data. The distribution details of electric field near ground are given out by the numerical simulation.

Calculation of step voltage near lightning current

The method to obtain the step voltage near a lightning current by calculating the near zone horizontal electric field was introduced in the first part of this paper. Then, the relationship between the step voltage and the peak value of the lightning current, the electrical conductivity of ground and the radial distance to the lightning current was investigated. Finally some discussions on the safety zone near a lightning current were made.

The definition of EMP shielding effectiveness

In this paper the experimental results of the interference and damage effects of plane-wave EMP and pulsed magnetic field on microcomputer and microcomputer measuring and control apparatus are introduced. Then some important conclusions are obtained, and, on this basis, the author presents the definition of EMP shielding effectiveness.