Studies Of New Kind Of Fast Adjustable Petersen Coil Grounded System

After analyzing the current states of the arc-suppression-coil (ASC) grounding system in the distribution networks in detail, the thesis presents a novel fast adjustable ASC system and a novel protection principle about selecting single-phase ground fault line in order to solve the dominating problems that the inductance of the existing ASC is not able to change quickly and the existing method about the selecting fault line is not greatly reliable. The ASC system and methods proposed in this thesis are correct because they are verified with the theoretical analysis, the simulation and experiment results. The primary achievements in the thesis are in the following:The thyristor phase-controlled mode is employed to make the fast adjustment of the inductance of the proposed ASC. However, the current of the ASC is distorted in the mode. The thesis analyses the relation of the distorted degree of the current to the change range of the inductance in detail. The novel adjustment mode, called the section adjustment mode (SAM), is presented. The SAM is adopted to increase the change range of the ASC inductance and to make the degree of the distorted current under the expected level without the designed filters. After theoretical analyzing in detail the conclusion is made in the thesis that the SAM is realizable. Under the guidance of the theoretical results the ASC system is designed and manufactured successfully. Without the designed filters the ACS system, comprising the thyristors with lower voltage level, is adjusted in the speediness, the continuum and the exactness. The researching results have become a patent.It is the innovation that the simulation software, SABER, is employed to design the novel ASC. In the simulation designs models of the magnetic path and the coil, developed in this thesis, describe not only the inherent characteristic of the elements but also the dimension of the devices. The material amount used in the device is also evaluated. The novel design method is the excellent solution for the simulation challenge that power electrical device and the magnetic path device are applied to the power system since it's the intuitionistic, effective and exactable. This method is also the innovation for the design and the application of the power electromagnetism device.According to the fast adjustable characteristic of the ASC system, the thesis creates a novel control method, which produces the fact that the existing control mode of the ASC systems that the distribution networks operate next to the resonant point is to beabandoned. The contents of the novel control method are in the following. When the system is in normal operation, in order to restrain the series resonant over-voltage, the inductance of the ASC is adjusted to the value that increases the over-compensation or under-compensation level. When the single-phase ground fault occurs, in order to extinguish Ihe arc, the inductance is adjusted rapidly to the value that causes the resonance. In the practice, the novel method is effective. In the novel method, the parallel or series resistors being employed for the over-voltage avoidance at the neutral point in existing ASC system are omitted, which solves many problems from the resistors.According to the fast adjustable characteristic of the ASC system, this thesis presents the novel method for the selection of the single-phase ground fault line in the network, in which the changes of zero-sequence currents of lines are employed to select the fault line. The novel method is also adopted in the proposed ASC systems. In practice, the fault line is chosen correctly by means of the novel method. The problem of the selection of the single-phase ground fault line in the existing ASC system has been solved successfully.Problems about the detection of the single-phase ground fault occurrence,the measurement of the line-to-ground capacitance and the design of the control system of the novel ASC are discussed in this thesis. The ASC system has been in operation and the behavour is good. The conclusio...