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Li T.,Tangshan Power Supply Company | Miao X.-P.,China University of Mining and Technology | Li X.-B.,China University of Mining and Technology
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control

In order to improve the compensation effect of the arc suppression coil, a new tuning method of arc suppression coil based on the constant zero-sequence voltage amplitude is proposed. In this method, the arc suppression coil and resistor are added in the distribution network neutral point. After replacing the resistor, it adjusts the arc suppression coil inductance value, while observes and measures the size of the neutral point offset voltage rms, to coordinate the further adjustment of the arc suppression coil. When the neutral point offset voltage rms is identical before and after replacing the resistor, simultaneous equations, the sum of the capacitance to ground C∑ and the sum of the resistance to ground gsum; in the distribution network can be accurately obtained, thus to determine the value of arc suppression coil fully compensated inductor L0. Matlab simulation and theoretical calculation verify that the method can obtain a more precise compensation effect. This method has the advantages of simple operation, high accuracy, good compensation effect, so it can be applied to the areas of arc suppression coil tuning. Source

Xin X.,Xian Jiaotong University | Li J.,Xian Jiaotong University | Ji H.,Tangshan Power Supply Company | Luo Y.,Xian Jiaotong University | Li Y.,Xian Jiaotong University
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering

Partial discharge (PD) is the main reason for the deterioration of the power transformer insulation. Partial discharge location is helpful to improve the safe operation of power grid. A combined sensor is designed to locate PD in transformer, and based on the sensor PD location simulation and experiments are made in this paper. The combined sensor includes a cross-shaped ultrasonic phased array of 13 array elements and a conformal 2 × 2 ultra-high-frequencies (UHF) electromagnetic array. The ultrasonic array can achieve the effect of 61 virtual array elements with high-order cumulants processing technology. It can greatly improve the aperture and direction sharpness of the array and reduce the cost of followed-up hardware. The expanded array and the UHF array were used to simulate to locate PD, the results are precise. And the noise suppression effect is compared with the multiple signal classification (MUSIC) method. Simulation results show that virtual expanding array has strong ability to suppress various colored noise interference. PD location experiments are made based the cross-shaped ultrasonic phased array, the results show that the locations are precise and its relative error is less than 5%. Virtual expanding to array with fewer number elements provides the possibility for the practical application of array technology in power equipment. © 2013 Chinese Society for Electrical Engineering. Source

Li Y.,North China Electrical Power University | Zheng W.,North China Electrical Power University | Wang C.,North China Electrical Power University | Wang F.,Tangshan Power Supply Company | And 2 more authors.
Gaodianya Jishu/High Voltage Engineering

The effective de-noising of partial discharge(PD) array ultrasonic signal is important for improving the partial discharge ultrasonic array detection. To avoid impacting array signal phase and amounts of calculation caused by the array signal denoising methods, we apply the matching pursuit algorithm to PD ultrasonic array signal de-noising. Moreover, we decompose and denoise each array element receiving signals on over-complete dictionary. There will be little phase distortion in the denoising process and only real signal will be extracted. The denoising results are evaluated quantitatively by the denoising evaluation index. The simulation shows that the direction-finding error of signal before and after denoising is more than 30° and less than 2°, respectively, and that the waveform evaluation index after denoising is available. The experiment show that the direction-finding error of signal before and after denoising is (6.525°, 6.863°) and (2.9°, 3.038°), respectively.The diagrams of the arrival spectrum directions and contour maps indicate that signal after denoising has a single spectral peak, which is the proof of the energy concentration. The results of the simulation and experiment show that the matching pursuit algorithm can effectively improve the signal-to-noise ratio and remove noise in the partial discharge array ultrasonic signal. © 2015, High Voltage Engineering Editorial Department of CEPRI. All right reserved. Source

Zhao L.,North China Electrical Power University | Zhao L.,Tangshan Power Supply Company | Qian Y.-C.,Tangshan Power Supply Company | Gu Q.,NARI Group | Chen G.-J.,NARI Group
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control

This paper proposes a new algorithm of state estimation to get the dynamic process of power grid after disturbance using fast, time-scale PMU measurements. The algorithm uses the results of traditional state estimation before disturbance as the initial state. The unobservable network for PMU measurements is equivalent. Once PMU measurements for generators are obtained, the varied dynamic process of power grid can be estimated. In the algorithm, the gain matrix is kept constant and factorized only once, which is favorable for dispatchers to monitor dynamic process of disturbed power systems. The proposed algorithm has been tested on a 7-bus system with a branch fault and the feasibility of the algorithm is demonstrated. Source

Zhao L.,North China Electrical Power University | Zhao L.,Tangshan Power Supply Company | Qian Y.,Tangshan Power Supply Company | Liu H.,State Grid Electric Power Research Institute of China | Li Y.,State Grid Electric Power Research Institute of China
Dianli Xitong Zidonghua/Automation of Electric Power Systems

One of the main differences between digital substation and conventional substation is the application of electronic transformer. In the substation electromagnetic environment, the occasional output abnormal data of electronic transformer will lead to incorrect behaviors of protections, and reduce the reliability of power supply. According to the characteristics for the abnormal data of electronic current transformer, an abnormal data resisting method based on sampling data amplitude comparison is proposed. The simulation results and practical engineering applications show that the proposed method has high reliability without influencing the action speed of protection. © 2010 State Grid Electric Power Research Institute Press. Source

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