Studies On Multi-source Wide-area Synchronization Measurement Based Fault Location Methods In Power Distribution Networks

The power distribution network is an important infrastructure that guarantees the economic development and residents' living standards.Since power distribution network is generally large sprawling and the environment along the distribution lines is very harsh,the short-circuit faults occur in power distribution network very frequently.The faults in power distribution network can easily lead to personal and equipment safety accidents,and directly lead to power outages.Accurate and reliable fault location is of great importance to reduce the fault restoration time and the power outage time.Power distribution network is almost radial and has large numbers of branches and sections.The fault-location technology for the power distribution network generally includes the selection of the faulted line,the identification of the faulted section,and the determination of the fault point.The main challenges for fault-location in modern power distribution network are the identification of the faulted section and the determination of the fault point.The existing fault-location methods for power distribution network generally locate the faults by using single type of measurement information,such as the frequency-domain information,the time-domain information and the traveling-wave information.However,the existing methods do not fully consider the complex scenarios of power distribution network,such as the presence of multilayer branches,the multiple neutral grounding ways,overhead line-cable hybrid lines,the distributed generations,the behindhand measurement technology,limited measurement point layout,and inaccurate line parameters.Therefore,the above challenges for fault-location have not been effectively resolved.In recent years,the development and application of the synchronous measuring device for power distribution network(D-PMU)and its wide-area measurement system provide advanced technical means for improving the level of the distribution network automation and the fault-location.This dissertation focuses on the fault location method for power distribution network based on multi-source wide area synchronization information: considering different types of D-PMUs and the different measuring point layout,this dissertation researches the principles and methods of the faulted-section identification and the fault-point determination by using different types of measurement information form D-PMU such as time domain and traveling waves,and solves the problem of fault location in multiple complex scenarios.The conventional D-PMUs are usually used in power distribution network,and are able to measure the transient digital signal with the sampling frequency of 10 k Hz.Therefore,considering the local limitation of measuring point layout and the inaccurate line parameters;this dissertation researches the faulted-section identification method;and then,this dissertation researches the fault-point determination method.In order to solve the problem of the faulted-section identification for the single-phase ground fault under the condition that the measurement points are locally limited,a comprehensive injection current of nodes based faulted section identification method is proposed.The local limitation of measuring point layout means that the measuring points are only installed at the network terminals.The proposed method uses the zero-mode current and voltage to calculate the zero-mode current for each branch and the comprehensive injection current of nodes.Then,a faulted-section-identification criterion based on the comprehensive injection current of nodes is constructed.The proposed method can accurately identify the faulted section when the measurement points are locally limited.In order to overcome the influence of the inaccurate line parameters on the fault-location.A time-domain fault-location method based on the identification of the coupled parameter identification is proposed.Considering the characteristics of coupling,a line model based on coupling parameters is established.Then,the identification-equation for the coupled parameters based on the coupled parameter model of the normal operating status and the fault-location equation are constructed based on the coupled parameter model of fault status are constructed respectively.Father,the pre-and post-fault multi-time measurement information and the fault history information are used to solve the equations.This method can locates the faults without the phase-model transformation and the accurate line parameters,the simulation fault-location errors are less than 150 m.At present,the novel advanced D-PMUs are able to measure the traveling-wave information.Thus,considering the local limitation of the measuring point layout,the global limitation of measuring point layout,and the high-voltage distribution network,this dissertation researches the traveling-wave-based fault-location method to further improve fault-location accuracy.In order to overcome the challenges of fault location caused by the local limitation of the measuring point layout,a K-coefficient-based fault location method is proposed.By using the travelling-wave arrival-times detected at each network terminals,the KB and KP coefficients which are independent of the travelling wave velocity are defined.Then,the faulted branch and the fault point can be located by using the KB and KP coefficient,respectively.In order to enhance the adaptability of the proposed method in the overhead line-cable hybrid power distribution networks,the traveling-wave-velocity conversion is used to convert the hybrid power distribution network into an equivalent overhead power distribution network.This proposed fault-location method is insensitive to the arrival-time errors,the traveling-wave velocity,and the distributed generations.The fault-location errors for on-site artificial short-circuit test are less than 100 m.Considering the global limitation of the measuring point layout,a multi-modal traveling-wave information based fault-location method for grounding faults in low and medium voltage power distribution networks is proposed.The global limitation of measuring point layout means that the measuring points are only installed at a part of network terminals.By using the arrival times of the modal traveling waves,a fault-location criterion which is independent of traveling-wave velocity is established.According to the characteristics of the false-fault-points,a principle of the measuring point arrangement is proposed.Further,the suspected faulted branches and the false-fault-points are identified by using the fault-location criterion and the arrival-time from multiple measuring points.In order to overcome the influence of bad data,the quartile method is used to detect the bad data to improve the fault-location accuracy and the robustness of traveling-wave arrival-time errors.This method does not require the synchronized time,and only require the measuring point installed at the parts of network terminals.This proposed fault-location method is insensitive to the traveling-wave velocity and the distributed generations.the simulation fault-location errors are less than 30 m.In order to solve the problem of fault-location of high voltage distribution network with complex loop networks,a wide-area traveling-wave-based fault location method is proposed.In order to solve the problem that the traveling-wave transmission path cannot be uniquely determined causing by the loop network structure,a loop-network simplification method based on online matching of travelling-wave arrival-times is proposed.This method can correctly match the traveling wave transmission path without fault simulations.Further,the fault distance and the traveling-wave velocity can be calculated by using least squares method and the redundant traveling-wave arrival-time.At the end of this paper,research work and results are summarized and the directions of further research are presented.