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Cai X.,Tsinghua University | Guo J.,Tsinghua University | Hu T.,China Academy of Machinery Science and Technology | Zhang Z.,China Academy of Machinery Science and Technology | Chen S.,Jiangxi Electrical Power Company
Yi Qi Yi Biao Xue Bao/Chinese Journal of Scientific Instrument | Year: 2014

Extremely low frequency (ELF) magnetic signal is usually used as the magnetic field source for tracking and location of mobile robots in oil and gas pipeline inspection, because the ELF signal is able to penetrate high permeability materials, such as metal pipeline, soil and rock. The diameter, thickness and buried depth of the pipelines vary with the circumstances in the tracking and locating engineering practice of inspection robots, which requires different types of ELF magnetic transmitters with different transmitting power. In this paper, the propagation rules of ELF magnetic signal and the engineering application of signal transmission and reception in the pipeline environment are combined together, and then a complete reverse optimal design method of the ELF magnetic transmitter is proposed. Firstly, according to the relationship between detection probability of the algorithm used in the ELF signal receiver and the corresponding peak SNR, the lowest peak SNR required by the receiver under a certain detection probability is derived, and then the minimal magnetic flux density at the front end of the receiver is determined. Secondly, the required minimal source magnetic flux density of the ELF magnetic transmitter in the pipeline is calculated reversely based on the minimal magnetic flux density at the front end of the receiver. Thirdly, the ferromagnetic core coil structure and circuit topology of the transmitter are designed under the constraints of the source magnetic flux density and the geometric dimension of the transmitter. The design result obtained with the proposed method not only meets the magnetic flux density requirement of the receiver, but also guarantees that the service life of the power supply for the transmitter greatly exceeds the required working duration in the pipelines. At the same time, even when the related parameters in practical circumstance change, the magnetic flux density at the front end of the receiver still meets the requirement of detecting ELF signal with high detection probability.

State Grid Electrical Power Research Institute and Jiangxi Electrical Power Company | Date: 2011-10-17

A method of power system preventive control candidate measures identification self-adaptive to external environment, which is applicable to dynamic identification of stations and power equipment under the effect of calamity, and judgment of preventive control measures that lose or restore control capability, and those for which control range or cost has changed. Automatic online identification of set of preventive control candidate measures includes two tasks: identification of stations and power equipment under the effect of calamity, and adjustment of the space of preventive control measures. According to information of power transmission line fault probability due to calamity, online dynamic quantitative assessment of stations and equipment is performed under the effect of external environment, and automatically correct control range and control cost of the measures according to the effect on equipment, so that the result of preventive control adapts to real-time external environment, ensuring feasibility and economy of auxiliary decision making.

Xie Y.,Nanjing University of Science and Technology | Xie Y.,NARI Group | Xue Y.,NARI Group | Xue Y.,University of Newcastle | And 4 more authors.
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2013

The impact of time-varying lightning on electrical equipment fault probability is analyzed. Based on the information to be acquired for preventing lightning disaster, a spatial-temporal variation forecast algorithm for power grid fault probability is presented. First, according to the lightning information of the current time interval, the lightning subareas are duly divided, which should be associated with the subareas in the preceding time interval. Then, according to the results, the trend of lightning fault probability in the next time interval is forecasted. The spatial-temporal distributed prediction probability is used to replace the traditional average annual lightning fault probability in the method which updates the envisioned fault table of the security stability analysis software online, enables the faults with greater probability to get detailed analysis in time and realizes the integration with power system security stability analysis function. The self-adaptive ability to deal with lightning disaster is added to actual projects of the blackout prevention system to improve the early-warning ability. © 2013 State Grid Electric Power Research Institute Press.

Liu X.M.,Jiangxi Electrical Power Company | Pan L.,Hunan Institute of Science and Technology | Zheng H.,East China University of Science and Technology
Applied Mechanics and Materials | Year: 2013

This paper presents a time Petri net model with the optimizing mechanism based on ant colony systems that addresses the problem of schedule optimization. The choice rules and pheromone update rules of artificial ants are embedded into the evolution rules of a time Petri net, so the modeling and scheduling analysis of real systems can be integrated into the same model. Compared with the approaches based on the heuristic search and genetic algorithms, our method efficiently unifies the modeling and analysis of schedule problems based on a time Petri net. © (2013) Trans Tech Publications, Switzerland.

Li Y.-S.,North China Electrical Power University | Guo S.-F.,Jiangxi Electrical Power Corporation | Ren G.-W.,Henan Xinyang Power Supply Company | Liu J.,North China Electrical Power University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2013

For analyzing doubly-fed wind power generation system and its operation characteristics in power grid accurately, its electromechanical transient models are developed. The mathematical model and pitch angle control model are established for components of doubly-fed wind power generation system including the wind turbine, mechanical device and doubly-fed induction generator. Based on its electrical-magnetic model, the models of converters control system of rotor and network sides are obtained, considering electromechanical operation characteristics. On this basis, the user defined (UD) models of doubly-fed wind power generation system in PSASP are constructed. The UD models are applied in the single machine infinite bus system for simulation. The results show that the models developed can reflect the transient characteristics of the system.

Du Z.,Wuhan University | Zhang Y.,Jiangxi Electrical Power Corporation | Ruan J.,Wuhan University | Ruan X.,Hefei Power Supply Company | And 2 more authors.
Gaodianya Jishu/High Voltage Engineering | Year: 2012

Heavy iced transmission line is one of the important factors threatening the safety and stability of China's power system. Difficulties of coupling between the tower and conductors and iced load handling make it difficult for the traditional calculation method to establish an accurate model to accurately calculate the unbalanced tension of tower-line system. Consequently, we used the beam element and cable element to establish an finite element method(FEM) simulation model of tower-line system by the ANSYS software, and analyzed the maximum stress, deformation of the towers-line structure by considering the ice thickness, wind direction, and wind speed parameters, and also analyzed the causes for collapsed towers under the condition of real uneven icing and wind. Moreover, the weakness of the transmission line was pointed out and modification proposals were presented based on simulation analysis. The simulation results of the 500 kV heavy iced overhead transmission line show that the proposed method is credible.

Fang J.-J.,Jiangxi Electrical Power Co.
Reneng Dongli Gongcheng/Journal of Engineering for Thermal Energy and Power | Year: 2013

In the light of such problems as low load variation speed, large fluctuation of the main control parameters and excessively low temperature of the main reheat steam existing in a 660 MW ultrasupercritical unit of Jingdezhen Power Plant owned by China Electric Power Investment Corporation, presented was an advanced solution to modern large-sized ultrasupercritical units adopting AGC control by organically fusing the predictive control technology and neural network learning technology with the self-adaptive control technology. By utilizing a INFIT (a PLC-based advanced thermodynamic control and application platform) real-time optimization control system, the control scheme above-mentioned was successfully accomplished on the spot. The practical application in the units shows that to use INFIT platform to realize the advanced control technology can obviously improve the load regulation performance, operation stability and average main and reheat steam temperatures of the units, thus enhancing in a comprehensive way the safety and cost-effectiveness of the units as a whole.

Wang H.,Jiangxi Electrical Power Corporation
Wuli Xuebao/Acta Physica Sinica | Year: 2012

Generation of triangular optical pulses in conventional normal dispersive (ND) fiber is experimentally realized using a passive nonlinear pulse shaping method based on a combination of pulse pre-chirping, group-velocity dispersion and self-phase modulation in a section of ND fiber. It is found that by optimizing the parameters of launching pulse power level and ND fiber length, high-quality triangular optical pulses with nearly constant gradients of leading and trailing edges and linear frequency chirp profiles can be obtained for a wide range of different pulse pre-chirping values. For different pulse pre-chirpings, high launch power is required for triangular optical pulse generation. The tolerance of triangular pulse formation to ND fiber length and launch power level is improved with the increase of pulse pre-chirping, which means that it is easy to obtain triangular pulses for higher pulse pre-chirping. © Chinese Physical Society.

Jiang X.,North China Electrical Power University | Wang Z.,North China Electrical Power University | Li C.,North China Electrical Power University | Tang W.,Jiangxi Electrical Power Corporation
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2013

A complex directional element adapting to wide area backup protection system is proposed. Firstly, the operation characteristics of positive-sequence fault component directional element and negative-sequence directional element are analyzed. Then a virtual variable quantity directional element is presented to cope with the drawbacks of the above elements. By creating virtual voltage and current, the virtual variable quantity directional element will produce the virtual variable quantities of voltage and current when a symmetrical fault occurs, which can be used to identify the fault direction persistently. Based on the three kinds of elements, the composition logic of the complex directional element is put forward. Finally, the simulation results demonstrate that the complex directional element can start reliably, operate accurately and keep effectiveness constantly to all kinds of short-circuit faults. And other advantages include no dead zone with a three-phase fault close to the element, high sensitivity with a strong source behind the element, and automatic return after external faults disappeared. Therefore, the complex directional element has a good performance to meet the requirement of wide area backup protection. © 2013 State Grid Electric Power Research Institute Press.

Huang B.,Jiangxi Electrical Power Corporation | Su W.-Y.,Jiangxi Electrical Power Corporation | Xu S.-S.,Jiangxi Electrical Power Corporation
Gaoya Dianqi/High Voltage Apparatus | Year: 2012

The GW16/17-550 outdoor HV disconnectors are widely used in the power grid. However, this type of disconnectors has such defects as contact overheating, movement block, and insufficient switch. Therefore, the internal structure of this type of disconnector is analyzed in this paper, some corresponding feasible measures are raised, and some disconnectors are subsequently modified successfully. Some suggestions about the design and manufacture of the disconnectors are as follows: (1) narrowing the gap between the positioning bolt of the active contact and the matched hole; (2) adding insulation part on the operation lever in the conductive tube and replacing insulation wheels by stainless steel wheels; (3) adopting non-welded structure and rustproof material, and adding an adjusting screw at the bottom of operation lever in the lower conductive tube; (4) applying sealant to the juncture of the upper and lower conductive tubes to prevent rain infiltration. The result shows that after transformation, the modified equipment runs well, and no recurrence of similar defects occurs.

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