When single-phase ground fault occurrs in extra-hgh voltage(EHV) transmission line with shunt reactors,the character of single-phase transient fault recovery voltage is different from the permanent fault.A method through analyzing the amplitude is developed to identify the recovery voltage,then the fault types can be distinguished according to the variation of the fault-phase voltage signals.The proposed method is simple,so it could be applied to the actual project.

Based on the complex network theory, the large-scale power system is described by the weighted network model. According to shortest electrical distance of nodes which belongs to this model, a method for operation mode combination is presented. The method makes use of the feature that shortest electrical distance of nodes represents the degree of their electrical association to find criterions for calculating fault current and branch parameters. And hereby the operation model of substations or plants with great impact on the setting values of relays will be considered, so finally achieve the purpose of optimizing the operation mode combination.

针对带并联电抗器的超高压输电线路,瞬时性故障时断开相恢复电压中存在由于储能元件初始储能引起的自由分量,该自由分量幅值接近或高于其稳态基波分量的幅值,频率低于且接近于工频,分析了单相瞬时性故障恢复电压的拍频振荡特点,提出了基于PRONY法对恢复电压信号进行快速辩识,通过得到的各分量的振幅、频率等信息能判别瞬时性故障与永久性故障,从而实现线路单相自适合重合闸。大量仿真结果表明该方法的有效性和准确性。

Along with the enhancement of power grid connection in China,it is possible for EHV/UHV transmission lines not to suppress power frequency over-voltage by reactors but by high speed grounding switches(HSGS)for fast arc extinction.In this paper the diffenret features of current signals passing through HSGS due to instantaneous single-phase earth fault and permanent fault respectively ale analyzed.Using Prony method,the current signals passing through HSGS are fast fitted every other power frequency period and the amplitudes of power frequency quantities can be extracted;then by means of analyzing the obtained series of amplitude information,it is discovered that for instantaneous fault the amplitude of power frequency quantity jumps from one stable value to another new value and the newv alue keeps stable,and yet for permanent fault the amplitude of power frequency quantity does not so behave,from this the nature of fault can be judeged.The Prony method possesses good fitting result for non-stationary signals and can implement the adaptive decomposition of frenquencies,in addition,it is sensitive to the variation of signals,so the defect of Fourier algorithm that the non-stationary signals cannot be processed is remedied.Simulation results by Matlab/Simulink show that the proposed methodis effective and correct.

Based on the characteristic of the power system and the advantage of multi-agent systems for distributed problems, the on-line setting system based on multi-agent technology is designed in this paper. The system can track the network status at real-time, and the setting of protection is reset and adjusted according to the change of the operation mode. The issue that with complexity of power network the setting of the off-line setting mode is not optimal can be overcome. In addition, the determination of the setting revision range, the real-time property of on-line setting and the synchronization property of setting modification are discussed and the solution is given in this paper.

Accurate and reasonable operation mode combination is of crucial importance for secure operation of power system.Along with unceasingly expanded scale of power network,it is hard for traditional combinatorial method of operation modes to suit to complicated network structure of modem power systems.In this paper based on the analysis on typical topological structures of power network that greatly impact the setting values,a combinatorial method of power system operation modes based on topological identification is proposed.According to four criteria,the transmission line disconnections,which greatly impact calculation results,are chosen with pertinence.Through calculation examples the setting results by traditional combinatorial method of operation modes are compared with those by combinatorial method of operation modes based on topological identification,and the effectiveness of the proposed combinatorial method is verified by comparison results.