scholarly journals Earthing Transformer to Support the Normal Operation of the Power System at Failure of a Protection System

2018 ◽  
Vol 182 (31) ◽  
pp. 1-6
Author(s):  
Yousuf Mohammad ◽  
Abdul Ghani
Keyword(s):  
Power System ◽  
Protection System ◽  
Normal Operation

The Solution for Malfunction of the Leakage Protection System Caused by Mine-Used Converter

2014 ◽  
Vol 912-914 ◽  
pp. 1481-1484
Author(s):  
Yan Wen Wang ◽  
Hai Hong Li ◽  
Da Wei Wang ◽  
Zheng Fan
Keyword(s):  
Power System ◽  
Coal Mine ◽  
Protection System ◽  
Normal Operation ◽  
Coal Production ◽  
Actual Situation ◽  
Matlab Simulation ◽  
Zero Sequence ◽  
Working Principle ◽  
Isolation Transformer

The leakage protection system usually trends to make a misjudgment and tripping in normal operation after applying the converter in the coal mine power system. This seriously affects the safety in coal production. Based on the research of the structure and working principle of the converter, it has obtained the definite reason for the converter interfere the leakage protection system. It is the higher harmonics and pulses that generate the zero sequence current through the ground capacitance. Combined with the actual situation in coal mine, it has proposed two corresponding solutions: one is adding the isolation transformer in the output lines of the converter; another is modifying criterion of the leakage protection system. Both methods have their own characteristics, and have verified the feasibility of the methods through the MATLAB simulation.

Reliable Analysis on Fast Valving of Ultra-Supercritical Unit Under Transient Fault Conditions

2017 ◽  
Author(s):  
Yu Cai ◽  
Wei Li ◽  
Bao Zhang ◽  
Wenjian Wu ◽  
Deren Sheng ◽  
...  
Keyword(s):  
Power System ◽  
Steam Turbine ◽  
Dynamic Model ◽  
Transient Stability ◽  
Power Grid ◽  
Load Shedding ◽  
Control Mode ◽  
Normal Operation ◽  
Transient Fault ◽  
The Stability

Fast valving of ultra-supercritical unit has great effects on over-speed prevention, load-shedding control, transient stability analysis of electrical system and other security problems. The purpose of fast valving is to maintain the stability of power system once fault or load shedding of unit occurs in the electric power system. Therefore, it is of great significance to study the reliability of fast valving for ultra-supercritical unit. In this paper, the KU ( short shedding) logic condition of SIEMENS T3000 system is analyzed as the research object of fast valving. The unit can be avoided over speed by monitoring the unit load and fast valving under faulty grid conditions based on the KU control. A series of measures will be taken after KU is triggered, for instance the governing valving will be closed quickly and the DEH (digital electro-hydraulic) control of the steam turbine will be switched to speeding control mode. On the other hand, the unit will return to normal operation if the transient fault of power grid disappears. The key contributions of this thesis include three parts: Firstly, based on the analysis of control characteristics of ultra-supercritical unit and protective logic and triggered conditions of KU function, a novel dynamic model by coupling the fast valving of steam turbine and the transient stability of generator is established by applying the PSCAD software. Then, the dynamic response process of ultra-supercritical unit is simulated and calculated by adopting the coupling dynamic model when KU function is triggered. Also the influence factors and reliability of fast valving are analyzed under transient fault conditions. Finally, two optimized measures by increasing the time delay and the speed of quantitative judgment are put forward to reduce risks and avoid the misoperation of signal distortion which may be caused by the power transmitter under transient fault conditions. The results of this study can not only help to evaluate the reliability of fast valving function scientifically in power grid transient fault, but also guide the technicians to analyze the stability of the power grid.

Harmonic Analysis of Non-Sinusoidal Harmonic Signals in Electric Power System

2014 ◽  
Vol 1070-1072 ◽  
pp. 779-784
Author(s):  
Dan Luo ◽  
Yi Xiao ◽  
Jie Na Zhou
Keyword(s):  
Power System ◽  
Harmonic Analysis ◽  
Short Range ◽  
Time Windows ◽  
Electric Power System ◽  
Normal Operation ◽  
Calculation Error ◽  
Interpolation Algorithm ◽  
Harmonic Signals ◽  
And Control

Harmonic Analysis and control is very important for the power system because harmonics have serious harm to its normal operation. Harmonic Analysis uses fast Fourier transform (FFT) to solve this problem though it causes the spectrum leakage which Increases the calculation error. To solve this problem, the interpolation algorithm combine with tapered time windows are used. The tapered time windows solve the long-range leakage and the interpolation algorithm solves the problem of short-range leakage.

New Research of Transformer Windings Partial Discharge Based on Non-Even Distribution Parameters Model

2014 ◽  
Vol 521 ◽  
pp. 343-346
Author(s):  
Yu Sheng Quan ◽  
Pu Xin Shi ◽  
Shai Gen Han ◽  
Ning Chen
Keyword(s):  
Power System ◽  
Partial Discharge ◽  
Normal Operation ◽  
Model Parameters ◽  
Distribution Parameters ◽  
New Research ◽  
Discharge Detection

Transformer is the primary equipment of power system. The normal operation of transformers has great significance of the security and stability of a power system. Once partial discharge happened in the winds of a transformer, it will accelerate the aging of the insulation, and may damage the windings. This paper analyzes the effect of partial discharge to transformer windings, and founding a model of non-even distribution parameters. Separate the even distribution parameters model into three parts and partial discharge happens in the second one. The partial discharge leads to changing of the model parameters. And port voltage changes with it. Partial discharge detection achieved according to the changing of port voltage.

Experiences on Remediation of Special Protection System for Kinmen Power System in Taiwan

2019 ◽  
Author(s):  
Ching-Jung Liao ◽  
Yen-Feng Hsu ◽  
Yung-Fu Wang ◽  
Sheng-Hui Lee ◽  
Yu-Jen Lin ◽  
...  
Keyword(s):  
Power System ◽  
Protection System ◽  
Special Protection

scholarly journals Study on Impedance Characteristics of Aircraft Cables

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Weilin Li ◽  
Wenjie Liu ◽  
Xiaobin Zhang ◽  
Zhaohui Gao ◽  
Meng Xie ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
Power System ◽  
Electric Power ◽  
Electrical Equipment ◽  
Electric Power System ◽  
Normal Operation ◽  
Variable Frequency ◽  
Forming Mechanism ◽  
Changing Trends ◽  
Impedance Characteristics

Voltage decrease and power loss in distribution lines of aircraft electric power system are harmful to the normal operation of electrical equipment and may even threaten the safety of aircraft. This study investigates how the gap distance (the distance between aircraft cables and aircraft skin) and voltage frequency (variable frequency power supply will be adopted for next generation aircraft) will affect the impedance of aircraft cables. To be more precise, the forming mechanism of cable resistance and inductance is illustrated in detail and their changing trends with frequency and gap distance are analyzed with the help of electromagnetic theoretical analysis. An aircraft cable simulation model is built with Maxwell 2D and the simulation results are consistent with the conclusions drawn from the theoretical analysis. The changing trends of the four core parameters of interest are analyzed: resistance, inductance, reactance, and impedance. The research results can be used as reference for the applications in Variable Speed Variable Frequency (VSVF) aircraft electric power system.

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