Influence Of Current Amplitude Research Articles

Influence Of Transmission Lines On Buried Pipelines Under Various Operation Conditions

Abstract Electromagnetic interference from transmission lines to adjacent pipelines can adversely affect the safe functioning of these pipelines. In this paper, a simulation model that the transmission line crosses the buried pipeline is established in CDEGS software. The influence of current amplitude, soil resistivity, and cross angle on the electromagnetic interferences are analyzed under different operation conditions of transmission line, including normal operation, short circuit fault and lightning fault. The analysis results are as follows: the soil resistivity has a great influence on the coating withstand voltage under the short circuit fault and lightning fault condition; with the increase of the current amplitude and the cross angle, the coating withstands voltage increases and decreases, respectively. These results indicate that, during construction, it is advisable to avoid parallel layouts of transmission lines and pipelines. Pipelines ought to be built in regions characterized by lower soil resistivity.

Vibration Feature Analysis for Gas-Insulated Switchgear Mechanical Fault Detection under Varying Current

As a key component to ensure the safe operation of the power grid, mechanical defect diagnosis technology of gas-insulated switchgear (GIS) during operation is often neglected. At present, GIS mechanical fault detection based on vibration information has not been developed. The main reason is that the excitation current is considerable but uncontrollable in the actual operation of GIS. It is difficult to eliminate the influence of excitation on the vibration amplitude and form an effective vibration feature description technology. Therefore, this paper proposes a unified feature-extraction method for GIS vibration information that reduces the influence of current amplitude for mechanical fault diagnosis. Starting from the GIS mechanical analysis, the periodicity of vibration excitation and the influence of amplitude are discussed. Then, combined with the non-linear characteristics of GIS systems and non-linear vibration theory, the multiplier frequency energy ratio (MFER) is designed to extract vibration-unified features of GIS for diagnosing the mechanical fault under different current levels. The diagnosis results of the experimental data with different feature-extraction methods show the applicability and superiority of the proposed method in the GIS’s mechanical fault-detection field based on vibration information.

Influence of current amplitude on the nonlinear asymmetric ac volt–ampere characteristics in amorphous ribbons with GMI effect

Asymmetric giant magnetoimpedance (GMI) effect in amorphous ribbons is very promising due to its possible application in developing the highly sensitive linear magnetic-field sensors. In this paper, the model of the nonlinear asymmetric volt–ampere characteristics in field-biased Co-based amorphous ribbon has been established through the time derivative of the longitudinal magnetization component in the ribbon. Its harmonics are also developed by Fourier analysis. The influence of the current amplitude on the nonlinear asymmetric effect has been studied. It is found that when the current amplitude is 8.54 mA, the sensitivity of the first harmonic voltage on the external field is equal to that of the second harmonic voltage. The results obtained are useful for developing the high-sensitive magnetic-field sensors.

Magnetically driven high current switching arcs in vacuum and low pressure gas

The behavior of high current switching arcs in transverse magnetic fields is essential for the design of switching elements, in which arc motion is used to reduce contact erosion. In this paper magnetically driven arcs in vacuum and low pressure gases are investigated at currents of several tens of kA. Arcs driven in a low pressure environment exhibit a peak arc velocity of more than 1/spl times/10/sup 5/ m/s, exceeding those of comparable vacuum arcs by at least two orders of magnitude. The influences of current amplitude, gas pressure, and the kind of gas filling on the arc velocity are investigated. A threshold behavior concerning the minimum requirements for a nonstationary arc is found. An improved model is presented, which explains the observed peak arc velocities in vacuum and in low pressure gases.

Calculation method for estimating thermal impedance for pulse current of power semiconductor devices

The described method is valid for arbitrary wave forms of the constant pulse current and for all diode, transistor and thyristor family devices whose thermal circuit can be modelled electrically by the serial connection of resistor-capacitor RC-pairs and whose forward characteristic can be approximated by slope resistance and threshold voltage. Temperature dependence of the device's thermal circuit parameters and temperature dependence of the forward characteristic parameters were not taken into consideration. The method enables an estimate to be made of the influence of current amplitude on the value of thermal impedance for pulse current.