The Research On The Measurement Of Capacitance Current In Resonance System With Following-Setting Compensation Mode

In the power networks with neutral point grounded by arc-suppression coil, the fault residual current in system could be reduced and the recovery speed of faulted phase voltage will decrease when single earth fault happens, which suppresses the damage of earth fault and arc fault and makes great contribution to medium-voltage power system protection. In usual case the work arc-suppression coil for compensating works in the state of approaching resonance. So it is also called compensated resonance power networks. The calculation of the capacitive current is the basis of automatic compensation. The arc-suppression coil must follow the change of the power network operation. When in the natural operation, the capacitive current is measured in order to adjust the arc-suppression coil eligibly. Apparently, the calculation precision will affect the compensated effect of arc-suppression coil. With the development of the technology and the application of various methods in the projects, there are a lot of ways to measure the capacitive current. Because of the complexity of the power network, a perfect capacitive current measurement that meets all kinds of circumstances hasn't yet been discovered.This paper has carried on deep analysis and studies to various kinds of capacitive current calculation methods of resonance ground system and compensation principles of arc-suppressing coil, and has pointed out the error that they exist in theory and the necessity of reducing the error. On the base of signal injection for the measurement of capacitance current, the paper takes the detailed analysis and points out the series-wound injection and parallel connection injection. Meanwhile it puts forward these injection methods on emulation mode and takes the error analysis. Besides of these, it puts forward the capacitive current calculation considering three-phase voltage imbalance in order to enhance the calculation precision by studying the influence of there-phases capacitance imbalance. For the complexity of signal transfers in the distribution network, the paper takes the analysis on the existing problems of sampling signal reversion and gives the settlements on the base of compare and test.The paper has also analyzed the influence the high-voltage side fault and asymmetrical fluctuation of load to the judgment of capacitive current change of resonance ground system, and has put forward the method, which judges to capacitive current change accurately. Finally, the paper introduces the design of the frequency conversion signal source which mainly used in the following-setting compensation mode and brings forward the suggestion to the problem existing while operating actually.