Fault Section Location And Type Identification Of Active Distribution Network Based On Synchronous Information

The complex structure of the distribution network and the harsh operating conditions make it very easy to cause faults.Timely and accurate isolation of fault sections is an effective means to improve power supply reliability,shorten outage time and reduce the scope of outages.According to statistics,single-phase ground faults account for about 80%or more of distribution network faults.At this stage,the processing of single-phase ground fault mostly stays in the fault selection stage,and the success rate of the selection is not high.At the same time,the power supply department has developed a plan to quickly isolate single-phase ground faults nearby.This sets a higher standard for distribution network fault section location technology.In addition,under the double carbon goal,China is committed to accelerate the construction of a new power system with new energy as the mainstay.The distribution network will also become a key link to improve the acceptance of new energy.However,as the distributed power sources represented by wind power and photovoltaic are connected to the distribution network,the original tidal direction and fault characteristics of the system are changed.There is a risk of failure of existing fault section location methods.It becomes more urgent to analyze the impact of distributed power access on fault characteristics and to propose a fault section location scheme applicable to active distribution networks.Existing studies also show that no single fault section location method can be guaranteed to work for all distribution network structures and all fault types.With the rapid advancement of grid measurement technology,the new generation of measurement devices such as PMU and WMU can provide electrical magnitude,phase and waveform data with uniform time coordinates.This greatly enriches the fault information needed to locate faults in the distribution network.The global measurement information is used as a breakthrough to construct multidimensional fault features,which can fuse the advantages of multiple fault features.This can,to a certain extent,make up for the problems of single in-situ information fault characteristics and poor interference resistance.In the above context,the study of single-phase ground fault segment location and type identification in active distribution networks is carried out.The main research contents are as follows.(1)A single-phase ground fault section location method based on waveform time-frequency matrix and energy relative entropy is studied.The fault transient characteristics and the influence of the distributed generation access on the fault characteristics are analyzed.The SSA algorithm is used to perform parameter search for the variational modal decomposition.The waveform characteristics of zero-sequence currents in different frequency bands are extracted by using variational modal decomposition,Hilbert transform and band-pass filtering algorithms to construct the time-frequency matrix.The relative entropy of zero-sequence current band energy of adjacent measurement points is calculated one by one.The relative entropy value of the band energy corresponding to the measurement points at both ends of the fault segment is the largest.(2)A single-phase ground fault section location method based on multidimensional fault feature extraction and matrix analysis is studied.Multipoint synchronous fault current waveform features are extracted from time domain,frequency domain and time-frequency domain perspectives.Referring to the results of the assignment of features by ReliefF and Random Forest algorithm,feature preferences are performed.The topology matrix is created by extracting the waveform features at each measurement point after optimization.Random matrix theory is introduced as a matrix analysis tool to map the topological matrix of all historical fault samples to the random matrix eigenvalue space.Samples with the same faulty segments are aggregated in the eigenvalue space.The fuzzy C-mean clustering algorithm is used to determine the spatial location of the centroids of each set of clusters.When locating a fault section online,the fault section can be determined by comparing the spatial distance to the center point of each cluster.(3)The distribution network fault type identification and single-phase ground fault hierarchical classification methods are studied.First,the three-phase voltage,zero-sequence voltage and three-phase current at the busbar are selected as the analysis objects,and the ICEEMDAN decomposition is performed and the time-frequency matrix is constructed.The singular value decomposition is performed on the time-frequency matrix.The singular spectral cliffness,entropy,mean value,and peak factor are calculated and used as feature vectors.The normalized feature vectors are fed into a multiclassification support vector machine for fault type identification.Second,the fault duration,fault point discharge and transition resistance as the entry point for the single-phase ground fault hierarchical classification.The characteristics of zero sequence voltage decay,the degree of zero sequence current distortion and the area enclosed by the phase space reconfiguration waveform are used as the basis for design classification.The detailed classification of single-phase ground fault is realized.