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Chengbei, China

Wang L.,Shanghai University of Electric Power | Guo S.,Jiaxing Power Bureau
Advanced Materials Research | Year: 2012

Harmonic pollution monitoring and control is the key to an accurate estimate of harmonic impedance, and thus an accurate assessment of public connection points of the harmonic emission level. This paper analyzes the link under the star-shaped and triangular three-phase asymmetrical power systems derived established a three-phase unbalanced power system harmonic impedance matrix estimation model. Model is based on a large number of systems and load the public connection point of the simulation data, the real and imaginary part of the harmonic impedance by opening and using grouping multiple linear regression method, on the system side harmonic impedance matrix to estimate the value of each element. Simulation and error analysis shows that the model obtained is more accurate and effective. © (2012) Trans Tech Publications. Source

Song X.,Anhui University of Science and Technology | Li P.,Anhui University of Science and Technology | Xu G.,Anhui University of Science and Technology | Li S.,Jiaxing Power Bureau | Guo J.,Anhui University of Science and Technology
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2013

In order to avoid the influence of excitation inrush current on transformer differential protection and further enhance the accuracy of transformer differential protection action, a method of excitation inrush current recognition based on recurrence quantitative analysis (RQA) was proposed given the nonstationary features of the transformer excitation inrush current and internal fault current signals. Firstly, the phase space theory was applied to show the inherent laws of inrush current and internal fault current signals in high-dimension phase space. Then the RQA method was used to extract the signal nonlinear characteristic parameters, i.e. recurrence rate, determinism rate, laminarization rate and entropy. The results show that the recurrence rate, determinism rate and laminarization rate of excitation inrush current are lower than those of internal fault current, but the entropy of excitation inrush current is larger, which means the regularity of excitation inrush current fault is lower than that of the internal fault current, and the chao is higher. Through the four characteristic features of RQA, the transformer excitation inrush current can be effectively identified. Source

Wang L.,Shanghai University of Electric Power | Sun Y.,Jiaxing Power Bureau
WIT Transactions on Information and Communication Technologies | Year: 2014

The single-phase ground fault in the nondirect ground neutral system (also known as the small current grounding system) is troubled by the old problem of power systems for many years. With the rapid economic development, China's power grid size has been greatly developed, about small current grounding system ground fault problem has evolved into one of the problems to be solved. This paper summarizes lessons learned on the basis of previous experience, proposed the use of zero-sequence current ratio method for fault detection, the method is based on the theory of neutral point grounding system fault line in the zero-sequence current equal to the other normal line currents and capacitor, resonant grounding in small current grounding system is inductive and capacitive current compensation current. Accordingly, through the fault line and non-fault line of zero-sequence current ratio of the difference, you can find the fault line. To neutral point noneffectively grounded distribution system, there are many methods to select the fault line: single-phase pull line method, variable frequency signal injection method, zero-sequence current law, these methods have their own characteristics, and they are respectively applied within a certain range or certain areas. Among them zero-sequence current is the most widely used in China to select the grounding line in distribution network. Most of the current microcomputer small current grounding line selection device is using this method. Its basic principle is that: capacitive zero-sequence current of the normal system is very small or zero. And grounding capacitive zero-sequence current occurs in the system when there is a single phase. © 2014 WIT Press. Source

Feng X.,Jiaxing Power Bureau | Qiu Q.,Jiaxing Power Bureau | Chen G.,Jiaxing Power Bureau | Ren Z.,Jiaxing Power Bureau
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2010

At present, most substation sequential operation schemes only consider primary equipment sequential operations, and operations involving secondary systems must be implemented manually by operating personnel on the field, which will result in temporary interruption of sequential operations. Taking the implementation of an isolator at the bus side of a 220 kV circuit breaker getting hot in double bus mode for example, secondary circuits are optimized for busbars switching, isolator operation and current transformer's secondary circuit switching. The operation hours of routine operations, sequential operations before and after optimization are compared. © 2010 State Grid Electric Power Research Institute Press. Source

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