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Research On Energy Coordination Between Surge Protective Devices In Low Voltage Distribution System

Posted on:2016-11-14Degree:MasterType:Thesis
Country:ChinaCandidate:Y LiuFull Text:PDF
GTID:2132330470469899Subject:Lightning science and technology
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Electrical and electronic equipments are extremely sensitive and tend to broken by the lightning electromagnetic impulse. Lightning could jeopardize high-voltage transmission and distribution equipments, electrical and electronic equipments in the buildings in a variety of channels. According to statistics, there are more than 70% incidents of lightning damage to equipment caused by the lightning comes from the supply lines. Overvoltage can not only cause electronic equipment misuse, but also cause permanent damage of electronic equipment, thereby causing direct losses and indirect losses. Installing reliable performance surge protection device (SPD) on the power supply system installation is one of the important methods to reduce the loss.It provides a theoretical basis for the lightning overvoltage suppression measures, according to the structure and characteristics of the low-voltage power supply system, analyzing the reason of lightning overvoltage, put forward to take advantage to the transmission of the wave theory and the principle of circuit theory equivalent model of the lightning wave transmission. In order to find out the energy cooperation method of ZnO varistor* the lightning propagation and inductance theories are analyzed. Based on the theories and experiments, the wire length was changed to get the needed inductance. The values of the distributed inductance of the decoupling components are equip to hollow inductance’s and magnetic core inductance’s. The following results can be got:when the connection wire length is 5m、8m、10m、12m、15m, the energy absorb ratios of the ZnO varistor are 83.82:16.18,88.64:11.36,91.27:8.73,93.17:6.83, 93.93:6.07 respectively after the experiments.And the residual voltages, current flow capacity and the energy absorb ratio are basically the same when the value of the distributed inductance of the wire is same with the hollow inductance’s. Because of the magnetic saturation of the magnetic core inductance, the energy absorb ratios of the ZnO varistor are 57.90:42.10, 62.05:37.95,60.52:39.48,58.97:41.03,61.84:38.1, when the values of the wire distributed inductance are 65.8 μ H,8.5 μ H,10.8μH,13.5 μH,16.3 μ H respectively. The research results have great significance in the applications of the ZnO varistors.For the energy coordination problem between the gas discharge tube and the varistor, the theory of transmission and circuit was used to analyze the character of the inductance in series in the circuit when the lightning impulse wave flow through it. The 8/20 u s lightning waveform was also carried on the experiment. Between the GDT and the ZnO is 3m、5m、7m、10m wire and equivalent inductance in series in the circuit. After the experiment, the following conclusions are get:the current flow through the ZnO will decrease with the increase of the length of the conducting wire. The conducting wire are equal to the inductance when their inductance value are same. Considering the phenomenon of the magnetic saturation, the inductance with magnetic core should be larger than that defined by the theory.According to the study of voltage limiting type surge protection devices, it provides several design approaches on various types of voltage limiting type surge protection devices:multi-chip varistors in parallel. It has some reference significance in the practical application of surge protection devices.
Keywords/Search Tags:surge protection device, zinc oxide varistor, impact test, lightning wave, aging of surge protection device
PDF Full Text Request
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