Time filter

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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.

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.

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.

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