High impedance faults (HIFs) are easy to occur in collective feeders in wind farms and may cause the cascading of wind generators tripping. This kind of faults is difficult to be detected by traditional relay or fuse ...
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ISBN:
(纸本)9781785618260
High impedance faults (HIFs) are easy to occur in collective feeders in wind farms and may cause the cascading of wind generators tripping. This kind of faults is difficult to be detected by traditional relay or fuse due to the limited fault current values and the situation is worse in wind farms. The mostly adopted HIF detection algorithms are based on the 3rd harmonic characteristic of the fault zero-sequence currents, whereas these 3rd harmonics are very easy to be polluted by wind power back-to-back converters. To solve this problem, the typical HIF arc flash based on Mayr's arc model is first built, and the typical fault waveforms of HIF in wind farm are presented. Then the characteristics of high impedance faults are analysed to distinguish the occurrence of HIF from other harmonic interference. After that, the performance of the traditional harmonic based HIF detection algorithm is discussed, and a novel detection algorithm is presented to prevent harmonic interference influence in wind farms.
As a new kind of lightning protection, parallel gaps have simple structure, easy installation, good economy, and many other advantages. The traditional parallel gap due to the large short distance, can lead to lightni...
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As a new kind of lightning protection, parallel gaps have simple structure, easy installation, good economy, and many other advantages. The traditional parallel gap due to the large short distance, can lead to lightning trip-out rate increases. Based on arc movement characteristics this paper presents a design of new type of parallel gaps and the analysis of the surface field strength, and the verification test, design a new kind of parallel gap are obtained.
Parallel gaps,as a new mode of "channel" type lightning protection,can do it with the sub insulator arc distance to effectively protect the insulator,but the corresponding line tripping rate will be affected...
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Parallel gaps,as a new mode of "channel" type lightning protection,can do it with the sub insulator arc distance to effectively protect the insulator,but the corresponding line tripping rate will be affected because of this;Development method based on the leader in this paper the calculation method of the lightning path,the typical used tower of guangzhou trip rate change after the application of parallel gap situation has carried on the analysis,got a short distance and adopt reasonable reinforced insulation,the trip rates did not rise significantly.
In this paper, the reliability of the rolling bearing fault feature extraction based on casing vibration signals is discussed. Through the fault simulation experiment of rolling bearing, the vibration data of the oute...
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By calling MATlab calculation engine function library,associated simulation between power System Analysis Software Package(PSASP) and MATlab can be realized in parallel and serial *** could use different timing sequen...
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By calling MATlab calculation engine function library,associated simulation between power System Analysis Software Package(PSASP) and MATlab can be realized in parallel and serial *** could use different timing sequence from PSASP,and mixed step simulation can be *** calculation method was used in a 10-nodes power system case for the modeling and simulation of Automatic Voltage Regulator(AVR),and the correctness of the proposed approach is *** this foundation,the electromechanical transient model of Static Var Generator(SVG) was founded with MATlab/Simulink,and it is of universal applicability and *** inner inverter model can also be used in general grid-connection simulating models of wind power generator,photovoltaic generation,energy storage,***,simulation and analysis for grid-connected wind farm by introducing the SVG model into PSASP were carried out via the proposed associated simulation method above,and the correctness of the model is verified via the calculation *** research results can be used to do assistant analysis for reactive voltage of grid-connected new energy powergeneration.
Aiming at the characteristics of the casing vibration acceleration signal of rotating machinery with rubbing fault, a diagnosis method based on EMD (empirical mode decomposition) and Hilbert envelop spectrum is put fo...
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Wind-photovoltaic-energy storage (ES) hybrid generating system has numerous reactive power sources. It is crucially important for coordinated control of these reactive power sources. According to the test results, the...
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Wind-photovoltaic-energy storage (ES) hybrid generating system has numerous reactive power sources. It is crucially important for coordinated control of these reactive power sources. According to the test results, there are unbalanced control problem in subsystem voltage of the hybrid generating system. The problem caused reactive power circulation and loop current. A subsystem voltage balance optimisation strategy is proposed to solve the problem. The case study shows the efficiency of the proposed strategies.
Electrical tree break-down is the major failure problem in cable accessories, however, mechanisms of the electrical tree initiation and propagation are still lack of deeply research, especially in silicone rubber (SIR...
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Very fast transient over-voltage （VFTO）, induced by disconnector operations in gas- insulated switchgears, has become the limiting dielectric stress at ultra-high voltage levels. Much work has been done to investiga...
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Very fast transient over-voltage （VFTO）, induced by disconnector operations in gas- insulated switchgears, has become the limiting dielectric stress at ultra-high voltage levels. Much work has been done to investigate single-strike waveforms of VFTO. However, little study has been carried out investigating the repeated strike process, which would influence VFTO significantly. In this paper, we carried out 450 effective experiments in an ultra-high voltage test circuit, and conducted calculations through the Monte Carlo simulation method, to investigate the repeated strike process. Firstly, the mechanism of the repeated strike process is proposed, based on the ex- perimentai results. Afterwards, statistical breakdown characteristics of disconnectors are obtained and analyzed. Finally, simulations of the repeated strike process are conducted, which indicate that the dielectric strength recovery speed and polarity effect factor have a joint effect on VFTO. This study enhances the understanding of the nature of VFTO, and may help to optimize the disconnector designed to minimize VFTO.
Obtaining the lightning strike density along an overhead transmission line and identifying the lightning strike types are the key to evaluating the lightning protection performance and proposing reasonable protection ...
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Obtaining the lightning strike density along an overhead transmission line and identifying the lightning strike types are the key to evaluating the lightning protection performance and proposing reasonable protection schemes of transmission lines. In addition, the waveform characteristics of lightning invasion overvoltage are the basis to establish the standard on the insulation tests of power equipment. Measuring the transient process of lightning striking overhead transmission lines is the basis to carry out the work mentioned above. In this paper, a distributed measurement method of transient current on conductors caused by lightning strikes is proposed. The measuring units are installed on the field conductors of transmission lines every 30 km to obtain less-distorted transient current waveforms. In order to enable measuring units to work in field isolated environment, a power supply coil using Faraday electric-magnetic effect and a wireless communication module is designed and developed. By far, 4776 measuring units have been installed on 597 transmission lines of China's power grid. According to measured transient current waveforms, the lightning strike point can be located using the double-end or single-end travelling wave location method, and the lightning strike type can also be identified. Moreover, a novel measurement method of lightning transient voltage based on the integrated optical electric field sensor (IOEFS) is proposed. In this method, the transient voltage waveforms are inversed from space electric field waveforms measured by IOEFSs. A series of performance tests of IOEFS have been carried out. The test results indicate that the response speed can reach several nanoseconds, and the frequency response can cover 5Hz∼100MHz which is wide enough for the measurement of the lightning transient voltage. In order to test the field measurement effect, the measurement equipment is used to measure a transient voltage when a group of capacitor voltage trans
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