Abstract:For XLPE cables, partial discharge can detect various insulation defects, However, when the partial discharge pulse propagates in the cable, the pulse waveform changes due to attenuation.A thorough analysis of the change of pulse waveform when cable partial discharge pulse propagates and the influence of different coupling bandwidths on signal detection is discussed.It is concluded that when cable partial discharge occurs, the amplitude of pulse signal follows.The increase of propagation distance decreases rapidly, but the attenuation amplitude of apparent discharge is relatively small; at the same time, broadband coupling has higher sensitivity, but its charge calibration curve error is larger and it will lead to the decrease of signal-to-noise ratio; although narrowband coupling can obtain more accurate charge calibration curve, it will cause pulse waveforms to overlap, affecting fault location.

Abstract:The cable very low frequency dielectric loss(VLF-TD) test technology has just started in China.The IEEE Std 400.2—2013 VLF-TD criterion is not fully applicable to localized XLPE cable of China.It is extremely urgent to carry out research on cable VLF-TD test.Therefore, the effectiveness of VLF-TD test for water tree degradation detection is verfied by accelerating water tree aging test and carries out on-site measurement.The 252 sets of data measured are classified and it is found that the cable line with a negative dielectric loss rate is in a state of attention or abnormality, and is mostly in an abnormal state.And the fluctuation value of the dielectric loss can more clearly and intuitively reflect the running state of the cable.Therefore, in addition to the three existing criteria of VLF-TD, the new characteristic quantity reverse dielectric loss change rate and extreme difference of dielectric loss are proposed, and the Korean Skirt dielectric loss criterion is absorbed, which is finally improved.The VLF-TD test criterion system provides a reference for the formulation of the VLF-TD aging state evaluation procedure for distribution cables in China.

Abstract:To study the influence of the change in elastic modulus of retried cable insulation on interface pressure, the breakdown field strength and dielectric loss angle tangent of cable insulation with different operating years are measured to characterize the electrical properties, as well as the mechanical properties of the elastic modulus at different temperatures.Based on the constitutive theory of hyperelastic materials, the interface pressure of new cable joint assembled on the cable is calculated.Meanwhile, a two-dimensional axial simulation model of the cable joints is established, and the axial distribution of interface pressure is analyzed.The comparisons between simulation and theoretical results show that the error of the interface pressure between the cable body and the joint is not more than 3.2% by using the two-dimensional axial simulation model.The accuracy of the simulation model can provide reliable data for studying the interface pressure distribution on the joint axis maximum.Although the electrical performance of the insulation layer of the cable of different operating years is different, and the difference of cable insulation elastic modulus with different operation year is 29%, but the interface pressure changes only by 0.275%.Therefore, when the new cable joint assembled on the old cable, the interface pressure is sufficient enough.

Abstract:The connector of the superconducting cable is one of the main factors affecting the life of the cable, in order to study the influence of the defects caused by the intermediate joints in the manufacturing and construction process on high-temperature superconducting cables.Therefore, based on the numerical calculation and analysis of electric field, the finite element method is used to simulate different defects and analyze the influence of three typical construction defects on the electric field distribution in the joint, such as the scratch of insulation layer, the impurity of insulation layer and the welding burr of superconducting tape.The result shows that the maximum electric field intensity decreases with the increase of air gap thickness when there is air gap caused by scratch of the insulating layer.When the insulating layer has the impurities, the electric field distortion around the impurities is the most serious.The tape welding position and the size of burr have great influence on the field intensity of the welded area.The three defect structure parameters have a great influence on the maximum field strength around the defect, and the structural parameter changes will cause a large change in the field strength.The research results can guide the construction process of the superconducting cable intermediate joint.

Abstract:Axial heat-transfer characteristics of gas insulated swithgear(GIS) cable terminals are important to the reliability and utilization of cable assets.The equivalent thermal circuit model is established, and its axial and radial heat-transfer characteristics are analyzed.A 110 kV GIS cable terminal high-current experimental platform is built, and a steady-state temperature rise experiment of 800 A to 1 200 A is performed to further analyze its characteristics.The results show that the axial heat transfer degree of GIS cable terminal is positively correlated with the load size.When the load is 1 200 A, the temperature to the high point is 93.0 ℃, and the maximum axial temperature difference is 15.4 ℃, exceeding the rated load capacity of the cable line.The analysis shows that the axial heat transfer of the GIS cable terminal is obvious, and the influence range is about 1 m behind the liner, and the conductor at the push spring section is the temperature to the high point.The influence weight of the ambient temperature on the GIS cable terminal and the cable body is the same and shows a linear rule.The research results can be used as a reference for power dispatching and operation and maintenance departments to evaluate the ampacity of cable lines.

Abstract:Cross linked polyethylene(XLPE) cables are commolly used in the power grid of mining area, but the operation environment is relatively bad and partial discharge(PD) of cables often occurs.Aiming at the problem of PD identification in the cable, the propagation characteristics of PD signal in XLPE cable are studied.According to propagation characteristics, method combining empirical mode decomposition(EMD) with Teager energy operator is proposed to identify the initial wave head of PD signal at both ends of the cable.The method greatly improves the ability of anti-noise in wave head identification.The radial basis function(RBF) neural network is used to train the training samples.Combined with the time difference between the PD signal and the measurement point at both ends of the cable, the accurate location of PD in XLPE cable is realized.PSCAD/EMTDC is used to build the cable simulation circuit.Simulation results show that proposed method has high PD identification accuracy and small identification error.

Abstract:Aim at the problem that the uncontrollable interference faced by the partial discharge identification in substation, and the initial parameters of the existing identification method are difficult to determine.Design defects that meet the discharge characteristics of the substation.Multiple sample datas are collected combined with the statistical characteristic parameters extraction method.Based on the Kohonen network with self-organizing competition recognition and strong anti-interference characteristics, new method suitable for partial discharge identification in substation is presented.By exploring the influence of the Kohonen network′s parameters on its recognition effect, the recognition effect is optimized.Then by comparing the network with the commonly used pattern recognition algorithm under the same conditions, high stability and high recognition rate of Kohonen network are proved, and excellent performance in partial discharge identification of substation is verified.

Abstract:Transmission line traveling wave protection uses traveling waves generated by faults to quickly identify faults, has ultra-high-speed action performance, and is not affected by factors such as power system oscillations, transition resistance, distributed capacitance current, and current transformer saturation.It is an ideal ultra-high voltage line relay protection method.Firstly, the development process of traveling wave protection is reviewed, and the domestic and foreign research status from three aspects of traveling wave signal extraction, signal processing technology development and engineering practice are summarized.Secondly, the basic principles of traveling wave protection are introduced and the advantages and disadvantages of various traveling wave protection principles are analyzed.The progress of related theoretical research is summarized, and a horizontal comparison and applicable scenarios for various traveling wave protection principles is conducted.Next, the main needs to be solved for the practical application of traveling wave protection technology problems are discussed and corresponding solutions are put forword.Finally, the development trend of traveling wave protection is prospected, which provides a reference for the subsequent research of traveling wave protection technology.

Abstract:The frequency unstability, voltage unstability and chain reactions could occur on renewable energy transmitted by ultra high voltage direct current(UHVDC) lines.Therefore, the theory, application and cases of power transmission technologies which are commonly researched and could be utilized in planning in China are analyzed.From the angle of alternative technology, the traits of half-wave-length transmission that act as a substitution of UHVDC transmission and can construct three-dimensional grid are put forward.Flexible DC transmission has preponderances such as practicability to organize DC network, which can be utilized in the scenes to admit renewable energy and establish DC network.The economy of two alternative technologies is compared based on the principle of annual fee per unit capacity.Conclusion is that flexible DC transmission costs less.Moreover, the choice of DC voltage level on the basis of least annual fees under diversified combinations of transmission distance and capacity is researched and analyzed.The characteristics of frequency modulation of virtual synchronous machine for new energy are analyzed as an assistive technology.Its application in new energy high permeability sending or receiving end power grid is presented.The dynamic reactive modification capacity of synchronous condenser is analyzed.Its application in transmission systems of new energy is presented.On the basis of trajectory of four alternative and assistive technologies and the variation of the pattern of power system in the history and anticipated, the tendency of technology development and influence on the shape of power system are discussed and forecasted.

Abstract:With numerous policies of energy storage participating in the peak and frequency modulation service been released, it is necessary to make clear analysis about those policies.Firstly policies and cases of battery energy storage system(BESS) participating in the auxiliary service of peak and frequency modulation are summarized from the national, regional and provincial sides, combined with the frequency and peak modulation characteristics of BESS.The admittance requirement, compensation price and trading mode in typical provinces are summarized.Then, the compensation mechanism for BESS participating in frequency modulation service in the United States and Europe, as well as two compensation mechanisms in China are discussed, and the modes and mechanism of BESS participating in peak modulation in China are summarized, taking Qinghai province as an example.Finally, the existing problems of BESS participating in peak and frequency modulation under the existing policies are briefly analyzed.Suggestions related to those problems are put forward from the aspects of differential compensation, optimal allocation of frequency modulation resources, the mechanism of energy storage sharing and evaluation standard.

Abstract:The fault recording data collected by the devices of both sides of transmission line, owing to the error in the sub clock, is asynchronous.The results of subsequent analysis based on the unprocessed fault recording data, especially the fault location, can not meet the requirement of accuracy, especially the fault location, failing to provide guidance for fault resolution.To make full use of fault recording data, time synchronization of recording data is very necessary.Firstly, three methods currently commonly used in engineering are shown, at the same time, the principle and limitations of every method are discussed.Secondly, the transmission line with lumped parameters model is established, a method based on least squares, using the parameters and recording data of the transmission, is proposed.Finally, the simulative results demonstrate that the time synchronization method based on least squares can achieve high accuracy in fault location, and improve reliability of subsequent analysis results.

Abstract:Unified power flow controller (UPFC) can realize flexible control of transmission line power flow, and improve system operation mode.However, the access of UPFC changes the uniform distribution of line voltage and brings some problems to relay protection.Based on the fault control and protection logic of UPFC, the transient variation characteristics of UPFC injection voltage are studied firstly.Then, the influence mechanism and degree of injection voltage variation on fault components based directional elements are studied.It is pointed out that when the protection locates between the fault point and the UPFC access point, the sensitivity of the direction element using positive sequence fault component and power frequency fault component can be greatly reduced.When a fault occures in UPFC, the direction elements may misjudge the fault direction.Based on the practical model and parameters of 500 kV UPFC project in southern Suzhou grid, RTDS simulation model contained UPFC control and protection logic is built.The theoretical analysis conclusions are fully verified by RTDS tests.

Abstract:Nowadays, the technology of the receiving end under hierarchical connection mode is widely adopted in the UHVDC project.With the affection of hierarchical connection mode, high and low-end reactive power is controlled respectively and core controller is put down to the valve group layer.How to optimize the mode of online valve group deblock and making it apply ripely into hierarchical connection mode should be explored urgently.This paper introduces the control strategy of online valve group deblock under hierarchical connection mode in detail, and points out the relationship between controller switch and trigger angle change in the process of online input.By comparing with the conventional one, it puts forward the new features of online valve group deblock strategy under hierarchical connection mode.It also indicates the key steps of online valve group deblock through the actual modeling and test support.The field test results show that the control strategy described in this paper is applicable to the existing UHVDC project under hierarchical connection mode, and the inverter station under hierarchical connection mode should open the BPS switch in a reasonable time interval to ensure the reliable operation of the valve group.

Abstract:Peak-valley time-of-use tariff is an effective price-based demand response strategy.Through reasonable time-of-use tariff, energy demanders can provide sufficient and efficient price signals, so as to achieve the goal of peak-filling of energy demand.The integrated energy system combines electricity, heat, cold, gas and other energy forms, and can achieve economic dispatch among different energy forms through a certain dispatching strategy.In this context, firstly, the energy hub modeling technology is used to achieve the effective modeling of the participating units in the integrated energy system.Secondly, the traditional research on demand response for electric load is extended to the research on demand response for cold and hot load, and a comprehensive energy demand response model including demand response for electric, thermal and cold load is established.The model is solved by using YALMIP/CPLEX optimization solver based on Matlab platform.Finally, the simulation results of different scenarios show that considering the comprehensive energy demand response in the context of time-sharing tariff is not only conducive to load peak-shaving and valley filling, but also has a certain role in improving the dispatching economy of the system.

Abstract:With the increasing demand of DC load, the topology of distribution system needs to be reconstructed in order to improve the reliability of distribution system.Two main ways to construct DC distribution system in the present situation include upgrading AC distribution system and constructing DC distribution system.Aiming at above two main ways, novel method based on reliability equivalent network is proposed.Compared with traditional failture mode effect analysis(FMEA) method, the proposed approach not only greatly reduces the calculation burden, but also ensures the accuracy of reliability evaluation results.The case study is carried out based on IEEE-RBTS test system.The availability of the proposed method is authenticated from the aspects of accuracy and efficiency through three steps, including discomposing DC distribution system, load-point reliability evaluation and distribution system reliability evaluation.The reliability evaluation results based on above two ways show that the construction of DC distribution system has higher reliability performance compared with upgrading AC distribution system.Therefore, facing the rapid growth of DC load, the construction of DC distribution system is recommended to satisfy the DC load demand.

Abstract:In order to give full play to the fast power handling capacity of the energy storage system and the regulation of the cold/heat load, promotes the active local consumption of distributed generations.A generation-load-storage layered coordinated control method is proposed, according to multi-time scale complementary characteristics of controllable distributed generations, energy storage systems and cold/heat loads.The method is oriented to the CCHP system, the scheduling process is divided into power layer and load layer on the basis of the principle of "allocating cold/heat energy based on electric energy".The two levels are coordinated and optimized according to the upper and lower levels, to determine the real-time dispatching scheme of electric energy and the real-time scheduling scheme of cold/heat energy.Through the actual situation of a distribution network in a park, scheduling simulation and analysis, the rationality and effectiveness of the generation-load-storage layered coordinated control method are verified.The scheduling results show that while ensuring the important electrical load of the park, the cold/heat energy is supplied to the maximum extent, so as to realize the coordinated optimization operation and the refined and intensive development of energy utilization.

Abstract:During the operation of distributed photovoltaic power generation, abnormal data collected by the operating system would be caused by interference factors, such as equipment failure, meter measurement error, user personal behavior and so on.Therefore troubleshooting abnormal data helps to ensure the accuracy and reliability of the PV generation user database and identify distributed PV users with operational problems.For the above reasons, an abnormal data inspection technology for photovoltaic power generation operation system is proposed.Environmental factors such as temperature, radiation, latitude, and seasonality are taken into consideration.The mathematical model of power generation is established by the central composite design method.The accumulated power generation is corrected by the extended Kalman filter(EKF) algorithm.Thus abnormal data can be checked and eliminated.The proposed method can realize the prediction of power generation data.It can check abnormal data quickly and reliably.The principle of investigation and the specific implementation process are discussed.Finally the effectiveness of the proposed technique is proved by experimental results.

Abstract:The main cause of transformer fault is insulation aging and damage caused by internal oil-paper insulation system under thermal and mechanical stress.The effect of thermo-mechanical combined stress on oil paper insulation is studied.Oil-impregnated paperboard is subjected to thermal aging at different times and different forms of mechanical stress are applied, and the strain generated by the paperboard under stress is measured.The effects of different loading conditions on the characteristics of withstand time, phase resolved partial discharge(PRPD) spectrum, average discharge capacity and other partial discharge characteristics were analyzed.The longer the stress loading time, the higher the stress amplitude or the lower the stress frequency, the more severe the damage of the oil-impregnated paperboard under the same mechanical stress, and the worse the mechanical insulation and mechanical properties of the paperboard.Under the action of thermo-mechanical accumulation, the effect of different mechanical stress is similar to that of unaged, but the morphology of PRPD spectra after thermal aging is mostly "rabbit-like".With the increase of thermal aging time, the insulation life of paperboard first increased, then decreased.The results of this study will provide a reference for establishing an aging model of oil-impregnated paperboard under thermo-mechanical combined stress.

Abstract:Lightning fault is one of the main reasons of transmission line faults, which is necessary to be predicted to reduce the loss caused by lightning faults.The accurate detection of lightning area has conflict with the accurate lightning prediction, which makes it hard to further improve the accuracy of lightning fault prediction based on current method.With the development of date mining technology, large amount of measured lightning information, historical lightning faults information, which are deposited in the database of power system for many years, can be utilized to predict lightning faults.Therefore, a lightning prediction method for transmission lines is proposed based on BP neutral network.Firstly, the input parameters of lightning faults are analyzed based on the historical lightning data.Then, a BP neutral network is employed to establish the prediction model, in which PSO is employed to calculate initial weight value and LM is employed to accelerate training speed of BP neutral network.Lastly, actual lightning information is adopted to verify the effectiveness of proposed method.Simulation results show that 80% of lightning faults can be predicted by proposed method which can provide a reference for power system operation.

Abstract:With the commissioning of UHVDC transmission lines in China, more and more attention has been paid to ground potential distortion and electromagnetic interference caused by direct current into the ground.Due to differences of soil structure in different regions, the distribution of surface potential is not the same.In order to study the law of surface potential distribution during unipolar operation of the Yanmenguan converter station, a three-layer soil resistivity model of Yanmenguan according to the field measurement using Wenner four-electrode method is established.Then the potential of substations, wind farms, and gas pipelines within 100 km of the grounding electrode at rated current is calculated.Simultaneously, the expression of the change of ground potential with distance is determined.Finally, the effects of injected current, soil resistivity, local resistivity and buried metal pipelines on the distribution of ground potential are studied.The simulation results show when the grounding electrode is a double ring structure, the ground potential decreases with distance.The injection current and soil resistivity have a greater influence on the surface potential distribution, and the buried metal pipes and local uneven resistivity have little effect on the surface potential.

Abstract:In recent years, large-scale photovoltaic(PV) grid connection has seriously affected the safe and stable operation of regional power grid.Ultra-short-term prediction of PV power can provide necessary data support for regional power dispatching and promote the realization of new energy consumption goal.However, the fluctuation characteristics of PV power make it difficult to improve the accuracy of power prediction.Therefore, PV power prediction model based on autoregressive integrated moving average(ARIMA) and support vector regression(SVR) considering power correction is proposed.Firstly, the ARIMA model is established using time series power data collected by PV power monitoring system, and preliminary prediction results can be obtained.Secondly, the prediction residuals of the previous meteorological similar day are used to establish SVR model to obtain the residuals of the prediction day.Finally, the preliminary prediction results are revised by prediction residuals.The typical PV power prediction models of different weather conditions are established by using the measured data.Test results show that the prediction accuracy is obviously improved after the residual error correction.

Abstract:Typical scenarios generating is one of methods for dealing with uncertainty of wind and PV outputs in power system planning and operation.However, the differences among output distribution functions at different times are not considered by the existing generation methods for typical scenarios.Given this background, in view of the uncertainty and correlation of outputs for distributed renewable energy generation, the differences among outputs′ distribution functions at different times are considered innovatively, the Copula function is used to establish the joint output model for multi-wind farm time-series.A large number of initial scenario sets are generated by probability sampling and splicing from the Copula model, and K-means clustering algorithm is used for reducing scenarios and generating typical joint output scenarios.Case studies show that the typical joint output scenarios of wind power are consistent with the correlation among wind power output and the differences among outputs′ distribution functions at different times.The output scenarios of multiple wind farms in the same area can be generated by the proposed algorithm with higher accuracy, which can guide the optimal operation of power systems more effectively.

Abstract:Aiming at the problem that the traditional PI controller used for the control of electric springs has poor adjustment performance and the control method does not take into account the sudden changes of non-critical loads, an smart load control method is proposed based on RBF neural network of the network on the basis of the mathematical model and control circuit of electric spring.The RBF neural network algorithm is used to make up for the shortcomings of the traditional PI controller that the parameters are fixed and cannot be changed.The real-time online adjustment of the controller parameters reduces the intelligent load instability and ensures the stability of the system bus voltage.Simulation verification in the simulation environment of Matlab/Simulink shows that, compared with traditional PI control, the intelligent load under the proposed control strategy has better performance in regulating the system.Therefore, the smart load under the new PI control strategy based on RBF neural network has better robustness and system control capability.

Abstract:Direct current(DC) transformer plays an important role in maintaining the stable operation of the DC distribution grid.Dual buck based modular multilevel direct current transformer(DB-MMDCT) is proposed in order to address the shoot through and dead time issue in the half bridge-modular multilevel direct current transformer(HB-MMDCT).The topology and operation principles are discussed.The leakage inductor current and the active power transmission property with different outer phase shift angles and inter-submodule phase shift angles per arm under the quasi square wave modulation scheme are illustrated.Furthermore, capacitor voltage balancing algorithm is given by sorting the capacitor voltages and their charge differences.At last, comparative simulation waveforms between the HB-MMDCT and the proposed DB-MMDCT are illustrated in PSIM when the quasi-square wave modulation is adopted.Results validate the priority of the proposed topology and effectiveness and validity of the corresponding control methods.

Abstract:Overheating of the transformer reduces the service life of the transformer.In order to analyze the heat dissipation performance of panel-typed radiators, a typical product of the panel-type radiator is taken as the research object.A method combining Fluent numerical simulation research with experimental verification is used.The heat dissipation performance of radiator under oil natural circulation and oil forced circulation conditions is studied.Oil flow resistance and oil average temperature rising coefficient are used to evaluate heat dissipation performance of radiators.The results show that when the oil flow rate is constant, the oil average temperature rising coefficientof air forced cooling is reduced by 0.17 than air natural cooling and better in heat dissipation under oil natural circulation.In oil forced circulation, within the range of oil flow 45 m³/h to 65 m³/h, when the oil flow rate is increased, the oil flow resistance is increased by 4 kPa, the oil average temperature rising coefficient remains basically unchanged, about 0.198, the heat dissipation of radiator is increased about 8.8 kW, the heat dissipation performance of panel-type radiator is increased.The results provide guidance for the optimal design of the fin radiator.

Abstract:Research on reverse recovery characteristics of high voltage thyristor induced by voltage pulse has important significance in parameter design, fault protection and test detection of converter valve.The thyristor two-dimensional semiconductor simulation model is built according to the actual structure of the thyristor.The static breakdown characteristics and reverse recovery current characteristics are simulated based on the carrier drift diffusion model.The validity of the model is checked by comparing with the experimental results.On the basis of the above, the device-circuit simulation hybrid model is established and the similarities and differences of the current density in the thyristor are analyzed and compared.The results show that voltage pulse can lead to the false triggering of the thyristor during the reverse recovery.The false tirggering voltage increases with the time at which voltage pulse is applied.

Abstract:Aiming at the problem that the weld area of the power station cooling pipe ray image has low contrast, the features are not obvious, and the traditional method is difficult to achieve an accurate search, a method for searching the power station cooling water pipe weld seam area based on deep learning is proposed.Contrast-limited adaptive histogram equalization(CLAHE) is used to limit the amplitude of the statistical histogram of the image and suppress the amplification of noise to obtain the cumulative distribution function(CDF) of the histogram to correct the low contrast of the image.The 24 convolutional layers of the deep neural network are used to extract the features of the input image, and the 2 fully connected layers predict the image position and class probability to achieve the detection of the welded seam area of the water-cooled wall tube and overcome the problems of the traditional template with low accuracy and high time complexity.The 100 refrigeration tube ray pictures were divided into training set, validation set and test set according to 4∶1∶5.The training set and validation set are used to train the deep neural network, and the position of the welding pipe area of the refrigeration pipe is predicted using the trained model.The experimental results show that the method of searching seam area based on deep learning can realize the precise search of the weld seam with an accuracy rate of 96% and high search efficiency and accuracy.

Abstract:When an external fault of busbar occurs, the current transformer(CT) of non-fault phase is saturated.In order to prevent the busbar protection from mal-operating, the method to identify the non-fault phase saturation of the faulty branch based on the current distribution coefficient is proposed.After identifying the non-fault phase saturation, the busbar protection is blocked.The method calculates the external fault phase current distribution coefficient of the power branch and the secondary fault phase current distribution coefficient of the power branch, and compares the calculation results of the two current distribution coefficients.If the calculation results are inconsistent, it means that the secondary fault is saturated by the non-fault phase.If the calculation result is consistent, it means that the secondary fault is internal or external.The real time digital simulation(RTDS) results show that the method can quickly and accurately identify the non-fault phase saturation of the faulty branch without reducing the operating speed of the busbar protection, and reliably prevent the busbar protection from mal-operating.

Abstract:In order to overcome the problem that the traditional distribution network fault location method has poor adaptability to distributed power generation(DG) access, and the need to configure a large number of measuring devices in the feeder to cause cost increase, a fault location method for multi-source distribution network based on correlation coefficient of current sequence component is proposed.Firstly, the superposition method is used to analyze the current characteristics and positioning principle of the fault point of the multi-terminal power distribution network.Then, the power terminal measurement device is used to obtain the amplitude difference of the output current of the power supply before and after the fault, and then assume that the fault occurs at different positions and calculate the theoretical value of the fault current of each power supply output.Finally, the correlation analysis method is used to calculate the correlation coefficient between the theoretical and measured data, and extract the two adjacent nodes with the largest correlation coefficient to achieve segment location.The improved IEEE 33 node model simulation measurement value is built by ETAP power system simulation platform.The Matlab programming is used to analyze the correlation.The result verifies the correctness of method.

Abstract:In view of the voltage quality problems of the distribution network caused by the access of distributed generations(DG), a multi-objective optimization model for the output of multiple types of reactive power sources in the distribution system aiming at minimizing active power loss and node voltage offset is built.And this model is oriented to DG and shunt capacitors.The restricted range of photovoltaic inverters and doubly-fed wind power generation to the grid is given considering the reactive power characteristics of photovoltaic power generation systems and wind turbines.The constraint condition function of the output of DG and shunt capacitors or the absorption of reactive power is constructed considering the constraint region of variables not crossing the boundary, bilateral crossing the boundary, unilateral crossing the upper boundary, and unilateral crossing the lower boundary.Using the sensitivity coefficient based on the power flow, a linearized model of the sensitivity coefficient of the objective function is obtained.The two-stage simplex method is used to solve the optimization problem with good results.At last, taking a three-voltage 60-node power distribution system composed of F20 and F32 lines in a certain substation of a power grid as a calculation example, the feasibility and applicability of the model and algorithm in this paper are verified.