The radiation and propagation of electromagnetic (EM) waves generated from PD caused by the obstruction of main transformer components are studied by FDTD simulation in order to get more information for PD location an...
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The radiation and propagation of electromagnetic (EM) waves generated from PD caused by the obstruction of main transformer components are studied by FDTD simulation in order to get more information for PD location and diagnosis. Current filament, perfect conductive cylinder and perfect conductive spiral coil models are used to simulate the radiation and the influences of iron-core and transformer coil to the propagation of EM waves. The results demonstrate dynamic propagation process of EM waves in time order, and prove the correctness of the shortest optical path principle. But the attenuation and distortion of EM waves-especially the first peak amplitude-caused by the obstruction of large solid conductive obstacle like iron-core are quite intensive that it may cause great difficulties to identify exact arriving time position of incident waves coming along the shortest optical path. While the influences of the coil to the propagation of EM waves are so little that HF EM waves can penetrate it in almost linear path.
Electromagnetic interference (EMI) on secondary de cable in cable tunnel due to a direct lightning strike in substation threatens the safe operation of electronic equipment and system connected to the cable. In order ...
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Electromagnetic interference (EMI) on secondary de cable in cable tunnel due to a direct lightning strike in substation threatens the safe operation of electronic equipment and system connected to the cable. In order to reduce EMI, the cable shield is generally connected to the grounding grid at both ends. Ground potential difference between two grounding points of the cable shield can be high due to high impedance of the grounding grid at high frequencies. In this paper, we present a hybrid method to analyze this complex system. As a result, both the current flowing in the cable shield and the transverse voltage between the cable core and shield are calculated. Compared with the measured results, the proposed method is demonstrated to be correct and effective.
A time domain electromagnetic field approach is proposed to investigate the lightning surge impedance of the full scale UHV tower with grounding system. The model, which is validated by comparing the result to those o...
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ISBN:
(纸本)1424401836
A time domain electromagnetic field approach is proposed to investigate the lightning surge impedance of the full scale UHV tower with grounding system. The model, which is validated by comparing the result to those of other method, can be used to analyze the lightning surge performance of a power line more accurately. Finally, this method is applied to analyze the surge impedance and potential of a real UHV tower.
In this paper, the status of the study on the voltage sags monitoring at home and abroad is summarized. Based on the GPRS wireless communication and Web technology, the dynamicmonitoring and data analysis system has ...
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ISBN:
(纸本)0863416381
In this paper, the status of the study on the voltage sags monitoring at home and abroad is summarized. Based on the GPRS wireless communication and Web technology, the dynamicmonitoring and data analysis system has designed for monitoring the voltage sags uninterrupted in a local network. The voltage sags in the receiving end network region are recorded, analyzed and counted by this system, at the same time, the information of these sags is transmitted to a remote computer using GPRS. This system can provide the policy-making support for alleviating the voltage quality questions. Based on Web, clients can login the service to scan periodical and non-periodical statistics reports of sag events.
In this paper,the authors propose a new space vector pulse width modulation(SVPWM)algorithm based on non-orthogonal coordinates for N-level ***,it is pointed out that classicalαβcoordinates-based SVPWM has many shor...
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In this paper,the authors propose a new space vector pulse width modulation(SVPWM)algorithm based on non-orthogonal coordinates for N-level ***,it is pointed out that classicalαβcoordinates-based SVPWM has many shortcomings because of improper coordinate ***,a non-orthogonal coordinates-based SVPWM is proposed to solve these *** proposed algorithm can easily identify which sector the reference space vector falls in and conduct simple operations to find the duty cycle of each ***,it is verified that the proposed SVPWM is actually a pulse−width modulation(PWM)technology based on line voltages.
A novel control strategy for 11-level cascade H-bridge APF based on TCPS-PWM is proposed in this paper. When the cascade inverter is applied to active power filter for distribution system, it is expected that the swit...
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ISBN:
(纸本)0863416381
A novel control strategy for 11-level cascade H-bridge APF based on TCPS-PWM is proposed in this paper. When the cascade inverter is applied to active power filter for distribution system, it is expected that the switching frequency and the EMI will be dramatically reduced below that of the traditional one. By the strategy, each power unit operates with relatively low frequency. At the same time, the equivalent switching frequency is still high so as to meet the high tracing ability for better compensation performance. This paper also focuses on the transposing modulation method to solve the problem of the balance of each DC voltage. PSIM is adopted for simulation of 11-level cascade H-bridge high-voltage active power filter which is to compensate the 10kV distribution system. Analytical and simulated results show the feasibility and superiority of the proposed strategy.
In this paper, an integrating schme to suppress the harmonics and compensate the reactive power based on the topology of thyristor controlled reactors (TCR) is presented. A new 10kV/500kvar dynamic reactive power comp...
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ISBN:
(纸本)0863416381
In this paper, an integrating schme to suppress the harmonics and compensate the reactive power based on the topology of thyristor controlled reactors (TCR) is presented. A new 10kV/500kvar dynamic reactive power compensation and harmonics suppression prototype made by placing a series of individual low voltage TCR reactive power modules in parallel and connecting them to the system through a multi-coil transformer has been developed. Experimental results have proven that the new euipment not only has all the advantages of the TCR but also very low level harmonics, which eliminates the need for suppression euipments. Furthermore, the cost is decreased and the reliability of the system is increased by avoiding euipments connected in series. A low voltage modular structure is adopted to increase the system capacitance and ease in augmenting the design. This equipment can solve the problems of large scale of load fluctuation and the serious excess of harmonic level.
Considering the displacement current in the multi-layer soil, the formulas of the ground return impedance and the Fresnel reflection coefficients are derived in frequency domain. These expressions are valid for discre...
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The constituent of Capacitive Voltage Transformer (CVT) are almost capacitances in primary side, and they act essentially as a short circuit to the transient current produced by a switching operation, which will gener...
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Overvoltage in powersystem restoration must be verified. The basic principle of VSC-HVDC (voltage source converter based high voltage direct current transmission) is briefly introduced. VSC-HVDC has such characterist...
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ISBN:
(纸本)0863412467
Overvoltage in powersystem restoration must be verified. The basic principle of VSC-HVDC (voltage source converter based high voltage direct current transmission) is briefly introduced. VSC-HVDC has such characteristics as flexible operation and control modes, independent control of active and reactive power, and operation on four quadrants. The overvoltage of the overvoltage between AC transmission line and the line connected with VSC-HVDC are calculated by theory analysis and simulation on PSCAD/EMTDC. The comparison of those overvoltage shows that the overvoltage of long AC transmission line connected with VSC-HVDC is lower than that of pure AC transmission lines. So the application of VSC-HVDC can enhance the speed of power grid restoration.
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