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Yan Z.H.,Ningxia Electrical Power Research Institute | Ren X.,Xian Jiaotong University | Ren H.,Xian Jiaotong University | Ding W.D.,Xian Jiaotong University
Applied Mechanics and Materials | Year: 2013

On-site experience suggests the possibility of condensation of the moisture in Current transformers (CTs) which is impossible theoretically if temperature distribution in the CT is uniform. In order to study the temperature distribution in a typical CT, finite element analysis software (COMSOL Multiphysics) is used to obtain the temperature distribution of the outer surface and inside of SF6 in CT in different ambient temperatures (20 °C to -10 °C). Besides, experiments are conducted to obtain the temperature of different positions on the CT surface that correspond to conductor, shell, spacer and porcelain bushing that are inside the CT with different ambient temperature. Both simulation and experiments show that temperature distribution in the CT is non-uniform, and the closer the part is to the conductor, the higher the temperature. Furthermore, maximum temperature difference remains about 35 °C in both simulation and experiments with different ambient temperatures from 20 °C to -10 °C. © (2013) Trans Tech Publications, Switzerland.

Chen N.,Hubei Engineering University | Wen X.,Hubei Engineering University | Lan L.,Hubei Engineering University | Huang L.,Central Southern China Electric Power Design Institute | And 3 more authors.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2011

The sag of transmission line, which influences the security and stability of power grid operation, is an important parameter in power systems. In order to monitor the sag of transmission line accurately, a novel calculation method for line sag based on power frequency electrical field (PFEF) inverse algorithm was presented. At first, a three-dimensional PFEF calculation model was established according to the finite slant charge method, in which the transmission line was expressed with the catenary equation. Then, according to the PFEF measured under the transmission line, the line sag was inverted with the help of genetic algorithm (GA) under the PFEF positive-going arithmetic model presented. Considering the impact of weather and survey condition for the measured data, a revised model based on least squares support vector machine (LS-SVM) was set up. With this model, the effect of outer factor to the measured data was reduced, and the modified measured data approached the ideal value. Since the revised measured data were used as the reference target values for the inverse algorithm, the calculation precision of sag was further improved. In the end, the effectiveness of the proposed algorithm was validated with the test of a typical transmission line in Yinchuan region. © 2011 Chin. Soc. for Elec. Eng.

Li X.,Ningxia Electrical Power Research Institute
Gaoya Dianqi/High Voltage Apparatus | Year: 2015

To investigate the inducement of porcelain bushing explosion of an SF6 insulated current transformer in operation, the finite element method is used to simulate the temperature field in the SF6 current transformer. Simulation and experimental results show that the temperature distribution is uneven in the SF6 current transformer, and the nearer the position to the conductor, the higher the temperature difference. The maximum temperature difference maintains about 35℃. ©, 2014, Xi'an High Voltage Apparatus Research Institute. All right reserved.

Chen N.,Hubei Engineering University | Wen X.,Hubei Engineering University | Liu B.,Hubei Electric Power Company | Lan L.,Hubei Engineering University | Li Y.,Ningxia Electrical Power Research Institute
Dianwang Jishu/Power System Technology | Year: 2011

To calculate power frequency electric and magnetic fields (PFEMF) generated by high voltage transmission line or space-crossing transmission lines accurately, based on charge simulation method (CSM) and Biot-Savart theorem, a universal model to calculate three dimensional PFEMF is built according to catenary equation, then the distribution of PFEMF under ordinary 330 kV double circuit transmission line on the same tower and that under the crossing transmission lines are calculated and measured. Calculation and measurement results show that as for the transverse distribution of PFEMF along the measured points perpendicular to the midspan, the results calculated by three-dimensional model under the calculation height of the conductor that is chosen as the minimum height above ground are very close to those calculated by two-dimensional model and are close to the measured results as well; at the projection beneath the crossing point of crossing transmission lines, the calculation results of PFEMF are close to the measured results, thus the effectiveness of the proposed calculation model of crossing transmission lines is verified. The causes leading to the error between the calculation results of PFEMF and its measured results are analyzed, and related factors influencing the calculation results by three-dimensional calculation model are emphatically discussed, and the reasonable number of divided conductor segments is given.

Chen N.,Wuhan University | Wen X.-S.,Wuhan University | Lan L.,Wuhan University | Luo J.,Zhuzhou Electrical Power Bureau | Li Y.,Ningxia Electrical Power Research Institute
Gaodianya Jishu/High Voltage Engineering | Year: 2011

In order to investigate the power frequency electromagnetic field distribution of transmission line crossed in space, a three-dimensional electromagnetic field calculation model of three-phase cross-wire was established according to the catenary equation and considering conductor sag and tower. Based on the charge simulation method, the power frequency electrical field below the cross-wire was calculated, utilizing linear finite slant line charges to simulate the axial charge distribution in wire. Based on the Biot-Savart theorem, the power frequency magnetic field below the cross-wire was calculated by finite thin current-carrying wire model. Meanwhile, the influence law of crossing angle and line-phase on field distribution was discussed. The calculation results show that the electromagnetic field below the cross-wire decreases with the crossing angle getting larger, and the field distribution changes with line-phase altered; the maximum electrical field occurs near the projection of the same phase cross-wire intersection, and the maximum magnetic field occurs near the projection of the intersection of middle phase of the top wire and side phase of the lower wire. Besides, the wire at the bottom plays a shield wire role in electrical field, however, for magnetic field, the role is related with crossing angle. In the end, the electromagnetic field is surveyed on the spots for two typical crossed wires in YinChuan area, and the availability of the algorithm is validated.

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