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Song X.-Z.,Beijing Sifang Automation Co | Wang L.,Zhumadian Power Supply Company | Zhi Q.-Z.,Luohe Power Supply Company
Dianwang Jishu/Power System Technology | Year: 2010

At present the acquisition of digital input signal and isolation of input signal from external electromagnetic interference for protective relayings are generally implemented by photoelectric coupling. On the basis of analyzing the principle of photoelectric coupling devices and the digital input acquisition circuit for protective relayings, which is designed according to this principle, it is pointed out that the error of digital input signal is mainly caused by DC system grounding in secondary system as well as the charging and discharging of distributed capacity of long cable. Qualitative analysis on acquisition error of digital input signal caused by insulation level decline under special condition is performed. Finally, according to the differences of consequence, it is suggested to divide digital input signals into such categories as direct-trip of protection, logic start-up, position indication, signal and so on. An idea of classification and testing of digital input signals is proposed, in addition, corresponding testing scheme and quoted standards are given. Source


Xu M.,Zhengzhou University | Wang X.,Zhengzhou University | Cheng F.,Luohe Power Supply Company
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2010

Recursive DFT(Discrete Fourier Transform) is normally used to dynamically calculate the frequency spectrum. According to the phase calculation, the power network frequency change is calculated to real-timely adjust the sampling frequency of measurement control device for synchronization. The spectral leakage caused by the truncated signals results in frequency calculation error and slows frequency tracking. A Hanning windowed recursive DFT method is introduced. The phase change of fundamental frequency in a frequency cycle is calculated by using Hanning windowed recursive DFT twice, with which the corresponding frequency change is calculated. The use of windowed recursive DFT effectively reduces the impact of spectral leakage and improves the accuracy and speed of phase change calculation. The proposed method has low computational complexity and fast frequency tracking speed, simple and easy to implement. Source


Li Z.,Luohe Power Supply Company
2010 China International Conference on Electricity Distribution, CICED 2010 | Year: 2010

The substation recording system is independent, the control center can not effectively monitoring on its operational status and cannot achieve more centralized management, cannot immediately find malfunction. So Put forward through the IP networking with straight unicom establish dispatching center of centralized management platform, make recordings in different geographic location of substation scheduling recording system can be recorded by the IP network to collect information on the server, users in the IP network in any site simply login server to other sites will be recording information query and maintenance management, so as to realize the substation of recording equipment and unified management, improving the scheduling recording system operation and maintenance convenience, timeliness. © 2010 Chinese Soc for Elec Eng. Source


Lin L.,Zhengzhou University | Liu X.,Zhengzhou University | Han Y.,Luohe Power Supply Company
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2012

The optimization model and algorithm for the maintenance scheduling of power supply equipments are studied. The optimization model takes the minimal sale loss as its objective. The power supply circuit price is introduced in the calculation of electricity sale loss to show the influence of different power supply modes in power market environment on the maintenance optimization results. The maintenance resource occupation is adopted in the terms of maintenance constraints to show the difference of resource occupation by different equipments in maintenance, making maintenance resource constraint accord with field practice. The holiday constraint is set to avoid or reduce the work in rest days. The improved genetic algorithm is applied in the equipment maintenance optimization to ensure its high quality. Case study shows the effectiveness of the introduced model and algorithm. Source


Gao D.-X.,Luohe Power Supply Company | Zhi Q.-Z.,Luohe Power Supply Company | Zhu L.-J.,Zhejiang Provincial Lishui Electrical Power Bureau | Liang X.,Tsinghua University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012

According to the characteristic of the typical smart substation communication architecture of three levels & two networks, this paper gives a configuration project of protect unit according to levels, and the interval protection such as line protection and transformer protection are arranged at the process level, whose trip does not rely on the digital switching system. Busbar protection is arranged at the bay level, whose protection function and trip depend on the digital switching system. A smart cell of protection and management is designed and configured at substation level to carry out all the back-up protection and run of substation. Line protection and transformer protection reserve the function of main protection, and smart cell of substation area accomplishes all the back-up protection. The scheme has panoramic data of all substation, and configures the function of protection over again, i. e. it can ensure that the main protection is not affected by system operation mode, can cut off fault component rapidly of the main protection, and also can solve the problems that the backup protection is influenced by system operation mode easily, configuration relationship is complex, operation time is long, etc., which constructs the safe and reliable first defense line of power systems of China. Source

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