Time filter

Source Type

Gong M.,Shandong University of Technology | Zhang Y.,Shandong University of Technology | Liu Y.,Shandong University of Technology | Wang Z.,Laiwu Power Supply Company | Liu L.,Yanshan University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2015

In order to improve the accuracy of fault diagnosis of power transformers, this paper presents a fault diagnostic method based on the back propagation algorithm evolving fuzzy Petri nets. Based on BP network algorithm, the optimization of FPN parameters can be determined when the initial value of weight of FPN on the arcs, threshold value and credibility is given. Using BP network algorithm with its capacity of self-learning and self-adaption, on FPN structure, the training is carried out on the sample data of DGA. Throughout the process, the value of FPN parameter approaches the real value. The results of numerical examples show that the algorithm proposed has good classifying capability of both single fault and multiple fault samples. At the same time, the correctness and effectivity of the proposed method are verified. ©, 2015, Power System Protection and Control Press. All right reserved.

Wang K.-X.,Shandong University of Technology | Chen P.,Shandong University of Technology | Gao Y.,Laiwu Power Supply Company
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012

For 35 kV and above high-voltage overhead-cable lines, the paper analyzes the wave propagation process and the wave's refraction and reflection phenomena after the failure. On this basis, the paper proposes a theory based on two waves combined ranging method. First, according to double-end principle, we choose the fault zone based on the initial wave arrival time errors at both ends in the mixed-lines fault. And then we use single-ended principles to give preliminary fault location. Finally, we give the accurate results by single-ended principles combined initial wave arrival time at both ends in the mixed-lines fault. The advantages of this method is that the results is obtained from single-ended ranging principle, eliminating the influence on accuracy by the mixed line length's error and circuit accurate time synchronization on both sides in the double-end principle ranging, so as to improve the accuracy and reliability of ranging. ATP simulations show that the proposed high-voltage overhead-cable's fault location scheme of combined wave is feasible and fault location accuracy is improved obviously.

Wu X.,China University of Petroleum - East China | Zhao R.,China University of Petroleum - East China | Ma S.,Laiwu Power Supply Company
Dianwang Jishu/Power System Technology | Year: 2013

During the Grid-connection of distributed generation systems such as wind farms and so on, it is necessary to make real-time detection of fundamental and instantaneous phase of power grid. The existence of harmonics with unknown orders in actual power grid is adverse to accurate phase-locking, for this reason by use of moving average filter (MAF) the extraction of fundamental components and orthogonal fundamental components in power grid can be implemented while harmonics are filtered. Considering the impact of fundamental frequency on MAF and taking adaptive notch filter (ANF) as the extracting unit of fundamental frequency, a MAF-ANF based method to extract fundamental phase under distortion occurred in power grid is obtained. Using the obtained method, the accurate extraction of fundamental phase under distorted grid voltage and harmonics with unknown orders existing in power grid can be implemented, meanwhile the abrupt variation of grid frequency can be fast tracked. Experimental results validate the effectiveness of the obtained method.

Pang Q.-L.,Shandong University | Gao H.-L.,Shandong University | Du Q.,Laiwu Power Supply Company | Wu Y.-B.,Laiwu Power Supply Company | Liu K.,Laiwu Power Supply Company
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2010

Owing to the smart distribution grid, the protection and control technology of the distribution grid is facing new opportunities and challenges. The Multi-Agent based protection and control algorithm for the smart distribution grid is proposed. Each intelligent distribution terminal (IDT) and control master are all regarded as one Agent respectively, and all Agents construct a Multi-Agent system through communication network. By information exchanging, IDT fulfills protection, fault location, fault isolation, network reconfiguration, power supply restoration and fault diagnosis, etc. The protection and fault location algorithms are discussed in detail. The simulation results show that this method is suitable for smart distribution grid, and has a high sensitivity and reliability.

Xiang M.,Shandong University | Gao H.,Shandong University | Zhao B.,Laiwu Power Supply Company | Wang C.,Laiwu Power Supply Company | Tian C.,Laiwu Power Supply Company
APAP 2011 - Proceedings: 2011 International Conference on Advanced Power System Automation and Protection | Year: 2011

The electronic current transducers based on Rogowski coil are now widely used in digital (smart) substations. But the high frequency response feature of Rogowski coil has not been fully developed, which results in a fact that travelling wave fault location technique can't be applied in digital substations yet. To improve this situation, this paper introduces Rogowski coil's transfer principle and structure features, studies two types of coil model - lumped parameter and distributed parameter, and then design a set of suitable coil parameters for travelling wave transfer. According to the coil's parameters, transient responses of two models are compared by computer simulations. To truly restore original traveling wave signals, a novel compound integration circuit is developed, which consists of an active integrator and a passive RC integrator. The active integrator works within low-frequency band, and the passive one works within high-frequency band. Finally, the frequency response characteristic of complete circuit containing both Rogowski coil and the compound integrator are obtained, which could show the transfer ability to travelling wave. © 2011 IEEE.

Xiang M.,Shandong University | Gao H.,Shandong University | An Y.,Shandong University | Du Q.,Laiwu Power Supply Company | And 2 more authors.
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2012

Data synchronization of digital intelligent electronic device (IED) with non-synchronous sampling of electronic transformers is studied. Based on derivative precise error formula of first-order Lagrange interpolation algorithm, each instantaneous error and phasor error of inside and outside interpolation algorithms are calculated, and the impacts to relay protection and measurement are also analyzed. First-order Lagrange interpolation error is related to sampling rate and offset time. But conventional reduce errors method is increasing sampling rate only. Through study on error variation rule with offset factor, and with using parabola equation to fit complex error locus equation by least square method under the certain error, the analysis is simplified. An adaptive adjusting basic time of interpolation algorithm is put forward which can effectively reduce error proved by verification. © 2012 State Grid Electric Power Research Institute Press.

Hao L.,Shandong University | Li Q.,Shandong University | Bi X.,Shandong University | Liu B.,Laiwu Power Supply Company
Gaodianya Jishu/High Voltage Engineering | Year: 2014

In order to further understand the mechanism of surface dielectric barrier discharge (SDBD) and illustrate regularity of the characteristic parameters of SDBD plasma, we established an equivalent circuit of asymmetric SDBD plasma generator based on the physical process of the discharge and some experimental results. Firstly, we derived a relationship curve between the plasma geometry and the voltage amplitude from images captured by high-speed camera. Then, using Matlab/Simulink as well as the Boltzmann equation solver, we solved the Kirchhoff's voltage equation and the electron continuity equation to calculate some characteristic plasma parameters, including current, electron density, electron temperature, plasma resistance, voltage drop across the discharge gap, and surface voltage of dielectric, etc, and hence obtained the influence of current density on these discharge parameters. It is shown with increasing current density, electron density and electron temperature increase but plasma impedance and plasma capacitance decrease non-linearly. The results can be used as a reference for further analyzing the discharge characteristics of the reactor, realizing impedance matching circuit, and improving the efficiency of plasma actuator.

Li Y.,Shandong University | Gao H.,Shandong University | Du Q.,Laiwu Power Supply Company | Qi X.,Laiwu Power Supply Company | And 2 more authors.
DRPT 2011 - 2011 4th International Conference on Electric Utility Deregulation and Restructuring and Power Technologies | Year: 2011

Distribution network feeders are very different from transmission lines due to more complex structures and more branches. The phase-to-ground faults in distribution network will induce larger transition resistance than in transmission lines. The traditional single-phase-to-ground fault location methods for transmission lines are no longer suitable for the distribution feeders due to the transition resistance and the branches' distributed capacitance. According to the investigation, single-phase-to-ground faults account for about 70% of all faults in distribution network. Therefore this paper surveys the singe-phase-to-ground fault location methods used both at home and abroad for distribution network, mainly including impedance method, traveling wave method, signal injection method, the zero-sequence component based method and compositive location method. The basic principles of the representative methods are present, and their advantages and disadvantages are analyzed. Then the main problems of the single-phase-to-ground fault location methods in distribution network are briefly expounded. Finally the future research ideas are proposed preliminarily. © 2011 IEEE.

Chen X.,Shandong University | Gao H.,Shandong University | Xiang M.,Shandong University | Zhao B.,Laiwu Power Supply Company | And 3 more authors.
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2014

Taking Rogowski current transducers and capacitor-divider voltage transducers as examples, differential output principle of electronic transducers is derived. The new method that uses the differential signals of electronic transducers is proposed to implement accurate fault location and high speed distance protection on the basis of ensuring the reliability. The impact of fault resistance is analyzed and it is proved that the improved R-L model algorithm is less affected. The simulation experiment, physical experiment and the dynamic characteristics of the algorithm verify the feasibility and effectiveness of the new method.

Gao H.,Shandong University | Pang Q.,Shandong University | Li S.,Laiwu Power Supply Company | Qi Y.,Laiwu Power Supply Company | Wang Z.,Laiwu Power Supply Company
Gaodianya Jishu/High Voltage Engineering | Year: 2013

In order to solve the problems of bad real-time performance, poor interaction and low reliability in self-healing control technology for traditional feeder automation, we proposed a multi-agent based self-healing control method for intelligent feeder automation. The master station and each intelligent distributed terminal are all regarded as an agent, respectively, and all the agents construct a multi-agent system through communication network. By information exchange among the agents, the fault location is carried out based on the improved differential current method, and the fault service restoration is realized based on the heuristic research algorithm. The algorithm takes the least load measurement of each service restoration path as its searching rule, aiming at the least load loss and the feeder load balancing. Then, based on the electromagnetic transient simulation software PSCAD, an actual distribution network is simulated. In the simulation, by using the improved differential current method, accurate fault location on both middle branch and boundary branch is realized; using the heuristic search method, all loads in non-fault power interruption area can be restored, and the restoration effect is similar to that of the traditional genetic algorithm, but the restoration time is shortened obviously. The simulative results show that the proposed self-healing control method can realize accurate fault location and quick fault service restoration, and it can be reliably applied to smart distribution grid.

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