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Xu J.,Shenyang University of Technology | Hao S.,Shenyang University of Technology | Lu Y.,Liaoning Province Key Laboratory of Safe Operation and Monitoring of Power Grid
2015 3rd International Conference on Electric Power Equipment - Switching Technology, ICEPE-ST 2015 | Year: 2015

Extra-high (EHV) transmission system has the characteristics of high voltage and large capacity, and a high amplitude current will be generated through the grounding line and ground net when failure occurs. Step voltage caused by the diffusion of fault current in soil is an important parameter affecting the normal operation of the system. The calculation and analysis of the step voltage in IEEE Std 80-2000 standard is rough, unable to reflect the soil surface potential distribution in substation comprehensively. This paper present an algorithm combined transmission line theorem and finite element analysis to calculate the electric potential distribution accurately, getting the attenuation law of surface potential and the step voltage. Analysis shows that the soil surface electric potential is well-distributed in normal operation and the step voltage is very small, only a dozen volt; The potential value can achieve kilovolt during short trouble and there will be a great attenuation within one meter; Soil resistivity, earth current amplitude and buried depth of ground net are the important factors influencing the surface potential distribution and step voltage. © 2015 IEEE. Source


Lin X.,Shenyang University of Technology | Wen M.,Shenyang University of Technology | Zhong S.,Liaoning Province Key Laboratory of Safe Operation and Monitoring of Power Grid
2015 3rd International Conference on Electric Power Equipment - Switching Technology, ICEPE-ST 2015 | Year: 2015

High temperature can cause many problems in OIP transformer bushing, such as aging of insulation and partial discharge, which will obviously reduce the lifetime of bushing. This contribution calculates the total loss in bushing under both voltage and current loads using the finite elements method(FEM) and then obtains the temperature distribution though the finite volume method (FVM). Computation results indicates that the total loss in 550kV bushing is 1203.89W, among which the 4.5% is dielectric loss. The peak value of temperature rise reaches 76.27 °C, which appears in the center pilot. Measurement of temperature rise is taken to check the calculation method, in which 16 points on the center pilot and nine points on the surface of umbrellas are taken into the comparison. Among the 25 compared points, error stays within 5% on 16 points, between 5% and 10% on 4 points, between 10% and 15% on three points. It can be concluded that the methods used in this contribution is proper and can support the designing and analyzing of OIP bushing. © 2015 IEEE. Source


Cao C.,Shenyang University of Technology | Cao C.,Liaoning Province Key Laboratory of Safe Operation and Monitoring of Power Grid | Lin X.,Shenyang University of Technology | Lin X.,Liaoning Province Key Laboratory of Safe Operation and Monitoring of Power Grid
2013 2nd International Conference on Electric Power Equipment - Switching Technology, ICEPE-ST 2013 | Year: 2013

For researching dynamic characteristics of circuit breakers(CB), aiming at a 12kV vacuum circuit breaker(VCB) with permanent magnetic actuator, the dynamic model of the vacuum circuit breaker is built based on virtual prototype technology. According to D' Alemhert's movement equations and Maxwell electromagnetic equations, the simulation is made on the vacuum circuit breaker in opening and closing dynamic processes. The experimental system is designed in order to verify simulation results. The opening time and the closing time of simulative model are 40.3ms and 55.2ms, simulative results are in accord with experimental data. Influencing factors of the closing bouncing and action principles of these factors are analyzed by dynamic simulation on the closing bouncing process. Analytic results indicate that increasing the preload and the stiffness coefficient of contact spring can limit the closing bouncing. © 2013 IEEE. Source


Li B.,Shenyang University of Technology | Li B.,Liaoning Province Key Laboratory of Safe Operation and Monitoring of Power Grid | Xu J.,Shenyang University of Technology | Xu J.,Liaoning Province Key Laboratory of Safe Operation and Monitoring of Power Grid
2013 2nd International Conference on Electric Power Equipment - Switching Technology, ICEPE-ST 2013 | Year: 2013

The lightning current might inject grounding grid through the grounding lead when the arrester suffered a lightning wave in substation. Then the ground potential difference(the difference of ground potential can/may) generated interference voltage on secondary cables due to earth potential rising. The interference voltage might lead secondary equipments misoperation and even damage. To analysis the problems mentioned above, a equivalent circuit model was established. The transient voltage caused by ground potential difference to secondary cables could be (can be or is) calculated by EMTP-ATP. As a validation, the impulse voltage generator was used as voltage source to simulate that substation encountered with the lightning, and to measure the interference voltage at cable terminal as well. Both experiment and computer simulation had been taken to analysis the influencing factors of the interference voltage on secondary cables and the ports of secondary equipments. The factors included the lightning current injection point and the soil resistivity rate. The analysis would provide a reasonable reference for wiring cables to improve anti-jamming capability of secondary equipments in substation. © 2013 IEEE. Source


Li H.,Liaoning Province Key Laboratory of Safe Operation and Monitoring of Power Grid | Li H.,Shenyang University of Technology | Lin X.,Liaoning Province Key Laboratory of Safe Operation and Monitoring of Power Grid | Lin X.,Shenyang University of Technology
2013 2nd International Conference on Electric Power Equipment - Switching Technology, ICEPE-ST 2013 | Year: 2013

According to an independent-developed motor operating mechanism of 126kV circuit breaker, the dynamic behavior was studied by simulation and experiment methods simultaneously. In this research, mathematical model of the actuator was established and dynamic load characteristics including equivalent moment of inertia and dynamic counter-force were analyzed in detail. Meanwhile, relationship between stroke of moving contact and rotating angle of driving motor was derived strictly. Based on the analyses above, transient magnetic field and dynamic parameters of driving motor were simulated by employing coupled field-circuit method which took the end winding leakage inductance into consideration. Opening and closing operation experiments were carried out by using the established test platform which combined motor operating mechanism with vacuum circuit breaker. The test results indicated that motor operating mechanism could be able to achieve opening and closing operation of 126kV vacuum circuit breaker reliably. The average closing velocity and opening velocity could reach 2.37m/s and 3.31m/s respectively, which totally met the requirement of vacuum circuit breaker. Simulation analyses of dynamic characteristics were in agreement with test results well. That verified the validity of the simulation analyses. © 2013 IEEE. Source

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