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Compared with other lightning target on ground, the most notable feature of wind turbine is that the blade will normally be in a state of rotation during lightning strike. In order to study the specialty and mechanism of the influence of blade rotation on triggered lightning ability, the paper conducted some lightning discharge comparison tests under different status of stationary and rotating blade...
There are many methods calculating the lightninginduced outage rate, however, which still exist many limitations. The method calculating the lightning-induced outage rate proposed by author is extended in these aspects: (1) The multiple orders Finite Difference Time Domain (FDTD) method is used to compute the lightning-induced overvoltage. (2)To closer to actual lightning conditions, we apply the...
Direct current through directly-grounded neutrals of nearby AC transformers may induce DC biases of transformers when high voltage direct current transmission (HVDC) system operates on ground return mode, thus producing negative impact on the AC system. This paper introduced the influence of DC bias to transformer and its research efforts. The suppression measures of DC bias were analyzed .
In order to investigate the influence of the lightning current that flows to the ground on the metallic pipeline buried below ground, this paper calculates the maximum transient voltage imposed on coating of the pipeline when significant levels of lightning current flow to the nearby earth by using the frequency-based model of grounding grids calculation and combining the forward fast Fourier transform...
Based on the mathematical and physical model of impulsive grounding, this paper constructed a computer model to solve this problem in an efficient and precise way. The solution of this problem was divided into 4 parts: the spectrum analysis of lightning current, the general frequency model for grounding device, fast calculation of impulsive response, visualization of the result. In the end, this paper...
A novel method that is been used to simulate the lightning progress process was presented. The base of the simulation the calculation of electric field intensity, the purpose of the simulation is to find out whether the lightning will strikes phase conductors or not. In the simulation model, the descending leader is been considered as cylinder discharge, and placing a concentrated discharge in the...
Mathematic model and equivalent variation equation of temperature Held is inferred. Base on the construction symmetry of ventilating system in hydro-generator, the model of analyzing stator temperature field is determined as the range of half tooth, half slot and half axial height. The hypotheses and corresponding border conditions are provided for simplification. In addition, heat conductive coefficients...
The design of such a novel software application that can be used to calculate the backflashover rate of transmission line is presented. The software application was developed by combining ATP with VC++. The software structure and the input/output interface are provided, as well as the implementation details. In the calculation, compares the insulators' volt-time curves to the overvoltage to judge...
Basing on virtual instrument model, a suit of system was designed for monitoring DC bias of transformer. The monitoring system can measure the DC current through transformer neutral using Hall current sensor, the vibration of transformer oil tank using piezoelectric acceleration sensor, the noise of transformer using capacitive acoustic sensor. The software was developed on LabVIEW. The system was...
Lightning shielding failure is the main factor to threat the safety and reliability of EHV transmission lines. In this paper, the small-scale model experiments of lightning shielding performance of EHV transmission lines were made, taking the various influencing factors into account, including protection angle alpha , the gradient of the hillside thetas, the height of the gully H , the conductor potential...
According to alternative grounding place situation of plusmn800 KV DC project, this paper selects the theoretically suitable place to design several different arrangement scenarios of vertical grounding electrodes and then compares the technical and economic performance when the sub-electrode length remains invariable while other parameters are changed and when the sub-electrode quantity remains invariable...
According to simulating test on the model sample by using high speed digital camera (10000 fps) and combining with finite elements analysis software, this paper studies the discharge process of discrete water droplets on the hydrophobic surface in the non-uniform electric field ( needle-board electrodes ) and computes electric field intensity along hydrophobic surface. The results show that the development...
Sudden short circuit is a serious transient process though it is short in time. In this paper, 3D transient equations of heat conduction as well as its equivalent functional equation are presented. Short circuit current of stator is performed. Sudden short current and heat of the stator are analyzed and calculated. Base on the construction symmetry of ventilating system in hydro the solution region...
At present, glass insulators and composite insulators are widely used in high voltage line owing to their outstanding features. In this paper, finite element method (FEM) is introduced and simulation modeling is outlined, and FEM software-ANSYS is employed to calculate the electric potential distribution of composite insulators and glass insulators under different conditions. The aim of the computation...
Nonlinear characteristics for the core of transformer is very important in computing exciting current or etc. a few of articles utilize the nonlinear characteristic unsuitably. For example, Phi ~ i curve is regarded to be conformable to B - H curve regardless whether magnetic coupling exists in the core. This paper discusses the relationship of the two kinds of curves for different structural transformer...
In this paper, the circuit model of three-phase transformer with three-legs under DC inrushing is set up. Considering the magnetic coupling of three legs, the nonlinear single-value curve of one leg of transformer is deduced. Combining the circuit equation and nonlinear B ~ H curve of one leg of transformer, we gain the wave and harmonics distribution of exciting current. Because of magnetic coupling...
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