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Yuan L.,Deyang Electrical Power Bureau | Du L.,Chongqing University | Wu J.-M.,Deyang Electrical Power Bureau | Cai H.,Deyang Electrical Power Bureau | And 2 more authors.
Gaoya Dianqi/High Voltage Apparatus | Year: 2011

Oil-immersed power transformers is the most critical devices of power system. and its failure diagnosis technology is deeply concerned. By analyzing a variety of data which reflect the current transformer operation conditions and according to the current transformer fault monitoring and maintenance status in power enterprises, a relationship between failure characteristic parameters and responding failure modes was established based on the structure of power transformers. Fuzzy mathematical method was employed to analyze the membership function of different electric test for transformer failure mode, hence the fixity and subjectivity in selection of the membership function and its parameters were overcome. The dissolved gas was first analyzed by three-ratio method to find the cause of fault, and then the fault probability was determine by the distance between the original to the coordinate fault point. Furthermore, by combining the characteristics of various parameters and introducing the gray correlation analysis to determine their weights, the fault probability of a transformer can be evaluated via the comprehensive diagnostic model. The examples show that this method is simple and accurate.

Zhijian Y.,Deyang Electrical Power Bureau | Yan L.,Sichuan Electric Power Corporation
Advanced Materials Research | Year: 2012

The impact of voltage sags on equipment is usually described by equipment failure probability. It is generally difficult to assess and predict the probability because of the uncertainty of both the nature of voltage sags and the VTL (VTL) of equipment. By defining the equipment failure event caused by voltage sags as a fuzzy-random event, a fuzzy-random assessment model incorporating those uncertainty is developed. The model is able to convert the probability problem of a fuzzy-random variable to that of a common random variable by using λ-cut set. It is thus valuable in theoretical analysis and engineering application. The validity of the developed model is verified by Monte Carlo stochastic simulation using personal computers (PCs)as test equipment. © (2012) Trans Tech Publications, Switzerland.

Deng H.,Deyang Electrical Power Bureau | Zhou N.-C.,Chongqing University | Wang Q.-G.,Chongqing University | Li C.-Y.,Deyang Electrical Power Bureau
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012

In order to reduce the impacts of grid-connected PV power fluctuations on the power system, a grid-connected PV power regulation system is built. The controlled microsource-microturbine is added to regulate PV power, realizing the grid-connected output power scheduled on the base of meeting the local load. To overcome the microturbine's shortcoming of slow dynamic response, the time series method is adopted to predict the power of PV and load. The output power of microturbine is scheduled in advance. Matlab software is used for simulation and verification, and the results show that the system proposed can effectively inhibit the fluctuations of grid-connected PV power, and improve the reliability of PV generation system.

Kang Y.,University of Sichuan | Li H.-Q.,University of Sichuan | Zheng W.,University of Sichuan | Kang N.,Deyang Electrical Power Bureau | Zhao L.,University of Sichuan
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2011

Based on the mathematical model of static energy function, this paper proposes a new voltage control partitioning method using fuzzy clustering analysis, which is established on the energy/voltage sensitivity matrix. With the energy information of nodes, we establish the energy sensitivity matrix (ESM) based on the tendency index of nodes. Then the ESM is decomposed to get the voltage control area by maximum tree method of fuzzy clustering analysis. It is used in IEEE 30 node system. The partitioning result is analyzed and compared with the other methods to demonstrate the validity and feasibility of the proposed method, and the obtained partitioning result meets the requirement of inter-area strong coupling and regional weak coupling.

Ma C.,University of Sichuan | Xiao X.,University of Sichuan | Yuan Z.,Deyang Electrical Power Bureau | Li C.,University of Sichuan
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2012

The Monte Carlo simulation assessment methods mostly adopt the classical probability measure or fuzzy measure to describe the occurrence possibility of cascading failures in power grids, and they need a large number of samplings to ensure a certain calculation premise. In order to avoid these deficiencies, a new fuzzy simulation assessment method to solve the occurrence possibility of cascading failures was proposed on the basis of credibility theory. Using the hidden failure model as the propagation mechanism of cascading failures, the physical and mathematical essence of cascading failures were analyzed in detail, and the credibility measure was applied to describe their occurrence possibilities. On the simulation analysis of the WSCC 9-bus test system and a western regional power grid, compared with some traditional methods, the results have proved that the proposed method can accurately identify the cascading failures with small possibilities only conditioned upon less sampling calculations, and it is characterized by adaptability, validity and accuracy. © 2012 Chinese Society for Electrical Engineering.

Zhang X.-X.,Chongqing University | Ren J.-B.,Chongqing University | Li Y.,Deyang Electrical Power Bureau | Liao S.-W.,Chongqing University | And 2 more authors.
Gaodianya Jishu/High Voltage Engineering | Year: 2010

SF6 partial discharge can generate stable decomposition components, which can be used to monitor the inner insulation in GIS. We compared the infrared spectrum (IR) by taking the pure SF6 and N2 as background gas and selecting the former for the IR detection background gas, obtained standard spectra and optimum absorption peaks of SOF2, SO2F2, SO2, CO, and calculated the absorption coefficients of the optimum absorption peaks. IR spectra were detected under five different partial discharge magnitudes after calibrating the partial discharge test device. It is found that there is critical partial discharge magnitude, there are different gas production rates with different discharge time and discharge magnitude. SOF2, SO2F2' gas production rates have rules with different discharge magnitude, which can diagnosed partial discharge level in GIS; moreover, the variation of SO2, CO' gas production rates is complex, but the single varying trend can still indicate the inner insulation condition.

Hu J.-L.,Chongqing University | Sun C.-X.,Chongqing University | Jiang X.-L.,Chongqing University | Li Y.,Deyang Electrical Power Bureau | Zhang Z.-J.,Chongqing University
Gaodianya Jishu/High Voltage Engineering | Year: 2010

Characteristics of surface DC arc on pre-polluted ice and icicle-icicle air gap DC arc under low air pressure is fundamental to the study on the discharge mechanism and the model of insulators under the combined conditions of high altitude, pollution and icing. We analyzed E-I characteristics of surface DC arc on pre-polluted plane triangular ice sample and icicle-icicle air gap DC arc under low air pressure in the low-temperature and low-pressure climate chamber. The results show that, the E-I curves of surface DC arc and icicle-icicle air gap DC arc are respectively in a negative power function relationship; the voltage of positive surface arc is higher than that of the negative one under the same conditions, while the polar of voltage has little effects on the E-I characteristics of icicle-icicle air gap DC arc; the E-I characteristics of surface DC arc and icicle-icicle air gap DC arc decrease with the decreasing air pressure, and icicle-icicle air gap arc is more remarkably affected by the pressure, compared with surface arc. The results can lay the foundation for the establishment of the DC discharge model of polluted and iced insulator strings under low air pressure.

Yong L.,Deyang Electrical Power Bureau | Lipin C.,University of Sichuan | Zhijian Y.,Deyang Electrical Power Bureau
China International Conference on Electricity Distribution, CICED | Year: 2012

When the power system component faults, the voltage sag duration depends on the cooperation time of protection system. Many literatures have analyzed the influencing factors of voltage sag magnitude, such as fault types, fault location, pre-fault voltage, transformer connections, and fault impedance. But the affection of protection cooperation to sag duration is not considered in detailed. A probabilistic modeling of the cooperation of the protection system is proposed based on the concept of Markov state space to estimate the sag duration. After that, the voltage sag frequency and sensitive equipment trip probability are estimated by utilizing the configuration and setting value of the protection system. The proposed method was applied to the IEEE 57-bus test system, and the simulation results show that the proposed method is practical, simple and adaptive, and the study of this paper has both theoretical significance and engineering application value for voltage sag frequency assessment. © 2012 IEEE.

Zhu L.,Deyang Electrical Power Bureau | Wei C.,Ertan Hydropower Development Company | Yu Y.,North China Electrical Power University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2010

DC bias will lead to half-cycle distortion of exciting currents. Then large quantity of even and odd harmonics will be produced. In order to research the effect of DC bias on single transformer and its protection, this paper uses PSCAD/EMTDC to create a simulation model. It simulates exciting current of a practical 750 kV single-phase transformer in variant cases under DC bias. It studies the relationship between the DC bias and distortion of exciting current, harmonic distribution, as well as the peak value of the exciting current. Meanwhile, the performance of transformer protection in this harmonic environment is analyzed. The loss made by exciting current's distortion and the elevated temperature of the core tie-plate are quantitatively calculated.

Yu Y.,North China Electrical Power University | Wei C.,Ertan Hydropower Development Company | Zhu L.,Deyang Electrical Power Bureau
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2010

The paper adopts PSCAD/EMTDC software to establish the system model and simulates the impact of DC ground electrode current on transformers of different structures including group transformer, three-phase three pole transformer, and three-phase fineplole transformer, etc. The results show that because of the independent magnetic flux circuit and small reluctance, group-type transformer is most influenced by DC bias; three-phase three-pole transformer which has no DC circuit and has larger reluctance is least-affected by DC bias; three-phase five-pole transformer in which area of iron core is smaller than that of single-phase transformer is impacted between the former two even though having DC circuit.

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