Advanced Materials Research Vols. 1070-1072

Abstract: Medium voltage in the electric power system of ship typically is powered by a large capacity transformer for low voltage electrical apparatus. When switching on, the primary side of transformer will produce very large current, which would endanger the safe operation of power for ships. The mechanism and characteristics of magnetizing inrush current is analyzed when the transformer switches with no load. We think that the reason caused magnetizing inrush current is transformers saturation. Pre-excitation is presented through a small volume transformer magnetizing method of suppressing the inrush current of transformer and validated by simulation and experiment.

Abstract: In the paper, electric field under overhead lines with human body existing is studied. The mixed method coupling finite element method with charge simulation method is constructed. Linkage of the finite element method domain and the charge simulation method domain is done by use of surface charge at interface. A simplified model with basic figure of human body is used. Calculation results show that human body has distortion effect on electric field nearby. Electric field at region very close to human body is greatly enhanced, while there’s little influence at region far away from the body. Head and upper side of human body play main roles of induction.

Abstract: A partial discharge (PD) signal processing method based on dynamic measurement theory and wavelet transform is proposed in this paper. The deterministic component was separated by polynomial fitting, and the random component of the remaining residual after the separation was estimated using autoregressive (AR) model; The true value estimate and dynamic measurement uncertainty of noisy signal were obtained by the deterministic component and random component;Db8 wavelet and the soft threshold based on Stein’s Unbiased Estimate of Risk were used to smoothly denoise for better PD signal processing. Finally, the effectiveness of the method was verified by MATLAB simulation and experimental noisy PD signal extraction.

Abstract: In order to study the electromagnetic interference on SAW (surface acoustic wave) wireless temperature measurement system of the corona discharge, the paper analyzes the characteristics of the frequency spectrum of corona discharge, models the corona discharge and studies its radiation characteristics by simulation on Matlab. Based on this, the experimental platforms of corona discharge is set up. The result of the experiment confirms that corona discharge causes electromagnetic interference to the system and the influence decreases as the distance between the sensor and discharge sources increase. Then the sensor should be kept a certain distance from the discharge sources.

Abstract: The software of measurement system for the transmission line debugging was designed. The transmission line is based on wireless communication. This software of measurement system is composed of acquisition controller software system and center station software system. The measurement system realized the function of data storage, waveform display, data analysis, automatic report generation and others. The field experiments were conducted at a 500kV substation in a Power Grid. The experiment proved the validity and reliability of the measurement system. The measurement system can avoid complex wiring work in substation debugging field, thus improve the experimental efficiency.

Abstract: When high speed rail run at high altitudes, over-voltage occurred in the process of operating makes the air gap of cable connector breakdown. It is necessary to clear the electric field intensity distribution and its numerical size of cable connector to make an optimization in order to curb this phenomenon. For this reason, 1:1 finite element model is established by the use of ANSYS software, and the simulation results show that the maximum value of the electric field intensity of cable connector can reach 644.05 kV/m. The maximum electric field is reduced with adding an insulating jacket to the head of cable connector. When the thickness of the insulating jacket is respectively 3 mm, 5 mm, 7 mm, 10 mm, the maximum electric field intensity percentage decreased is 10.26%, 11.4%, 16.1%, and 16.7%. So the insulating jacket would be an effective measure to inhibiting the breakdown of the air gap at the cable connector.

Abstract: Substation noise pollution as one of the most important environmental problems has been paid more and more attention. A model of substation sound barrier is built in this paper. On the basis of the model, the effects of sound isolation of the barrier with different positions, different heights are analyzed. The setting of the sound barrier that can bring best sound insulation effect will be obtained from the simulation results. Moreover, as the substation control buildings can be seen as barriers, the analysis of the sound barrier attenuation can provide a certain basis for the layout of substation buildings, and the setting of noise reduction barriers for noise controlling.

Abstract: The article is dedicated to investigate possibility of diagnostics bearing faults of induction motors by stator currents analysis. The main features of stator currents analysis are studied. The possibility of identifying air-gap eccentricity due to the working with damaged bearings by stator currents investigating is revealed. The recommendations of monitoring and configuration of a proper diagnosis of induction motor are provided.

Abstract: This paper analyzes the static characteristics of induction motor. The models, as well as typical parameters, of induction motors for stability analysis are introduced. The slip-voltage curve, active power-voltage curve, and reactive power-voltage curve are obtained for analyzing possible operating states. According to the number and the stability of operating states, induction motors are classified to three kinds.

Abstract: The assessment of operating state of the generator is an important means to guide the generator overhaul and improve the reliability of power system operation. The traditional pattern is gradually replaced by the real time state assessment model, this paper which is based on the multilevel nature and multivariate of the generator information establishes the state assessment system of the generator and uses extension level assessment method to assess the comprehensive state of the generator. Examples show that the method has a strong rationality and effectiveness.