Research On Fault Diagnosis And Location Technology Of Active Distribution Network

The multi-brunch structure and load diversity of distribution network show the complexity of distribution network.Also,the power flow direction and fault characteristics of distribution network have changed with the integration of the distributed energy resource,which makes the distribution network gradually transformed into active mode,and the adaptability of traditional protection method is meantime reduced.Most of the faults in distribution network are single-phase grounding faults,which can still last for a period of time.The phase-to-phase fault will appear under the condition that the single-phase fault couldn’t be found and isolated in time,and power outage area will expand and personal safety and social production be endangered.To ensure the safety and stability in operation of distribution network,it is necessary to study different fault processing methods so as to improve the reliability of power supply.In this paper,different diagnosis and location methods are studied under active distribution network by means of distribution automation system,and the main research of this paper is as follows:Aiming at the single-phase grounding fault of small current grounding system,a diagnosis method based on the transient signal of nodes of feeder line is proposed.Wavelet packet decomposition is firstly used to extract the characteristics of the measured current signal of distribution terminals.Based on wavelet packet energy and frequency band of different signals,the composited similarity is calculated which contains amplitude and waveform similarity.The adaptability of the proposed method is verified under the condition that the fault occurs in main line and branch line respectively.The simulation results show that under the condition of different grounding resistance,different fault angle,and different accessibility of distributed generators,the fault can be diagnosed accurately.As for the convergence problem of fault location based on intelligent algorithm,taking ant colony algorithm in fault location of distribution network as an example,double elite ant strategy is adopted as the improved algorithm,and the line pheromone concentration is adaptively updated.By dividing the distribution network into different parts,the dimension of fault search is decreased,and the convergence of the algorithm is improved while the locating speed is under controlling.Besides,the missing and distorted information uploaded by the distribution terminals is considered,and the correction method is proposed.Finally,based on the program in MATLAB,the simulation under different condition of faults is conducted to verify the accuracy and error tolerance of this method.The synchronous phasor measurement technology applying to fault location and distance measurement is studied,and the high-precision synchronous phasor measurement device is adopted to improve the real-time performance and accuracy of measurement signal.Also,the optimal configuration scheme considering its cost is put forward.Then the calculated values of short-circuit current in different segments are obtained based on the system impedance matrix.And the fault distance is calculated by the measured phasors of line ends,without knowing the grounding resistance.The IEEE33-nodes system is established under the DIGSILENT Powerfactory simulation tool,by which the experiment conducted verifies the accuracy and adaptability of the propose method.