Advanced Materials Research Vols. 732-733

Abstract: State Grid Corporation of China has carried out research on key technology of UHV&EHV AC and DC multi-circuit transmission lines, the research on material and structure of transmission tower is the important part. The SSZT2 tower, on which 1000 kV AC double-circuit and 500 kV AC double-circuit are arranged, is the largest power transmission capacity all over the world. Q420 high-strength tubular steel, the plug-in boards and forging flanges are used in SSZT2 tower,and the forging flange with strength classification is applied for the first time. Through the monographic study on the tower structures, wind vibration coefficient, and biaxial bending of steel tube etc. The success of full-scale test verified the reliability in design and manufacture of multi-circuit steel tubular tower for UHV and EHV. Research results of this paper can be applied in UHV transmission line projects.

Abstract: The insulation mechanism of UHVDC wall bushing is discussed. Design solution of the insulation structure is determined. In the solution, internal insulation includes SF6 gas-insulated and shielding structure, and external insulation is a type of composite insulating material, which is made up of epoxy FRP pipe and silicone rubber sheds. Creepage distance of external insulation and two types of shielding structures are designed in the paper. Finally two types of shielding structure are compared and optimized based on electric field simulation, and the result shows that dual-plate grounded shielding can enable the electric field strength of UHVDC wall bushing more evenly distributed.

Abstract: Since the existing fault phase identification methods can not identify all fault types quickly and accurately for high voltage transmission lines, this article proposed a new method of fault phase identification based on the fault component of phase voltage difference and the kalman filter algorithm. The method defined the fault components ratio of one phase voltage to the difference of the other two phase voltages as a fault phase identification factor. By analyzing the characteristics of fault phase identification factors in each fault type, the fault phase can be identified. Simulation results show that using the kalman filter algorithm to extract fundamental component is faster and more accurate. Meanwhile, the method can identify fault phases within half a cycle and is scarcely influenced by fault resistances, fault locations and fault initial phase angles. It also has a high sensitivity when the fault is on the side of strong source.

Abstract: High Voltage Direct Current transmission (HVDC) will cause torsional interaction under certain conditions. Among a variety of factors, improper rectifier control has fateful effect. In the paper, the test signal method which is the time-domain form of the complex torque coefficient approach (CTC approach) is studied. Its application conditions in multi-machine systems are summarized. Using the test signal method, impacts of DC power, DC voltage, rectifier controller parameters and generator output on electrical damping characteristics in the Suizhong system are studied based on time-domain simulation model.

Abstract: The short-circuit electromagnetic force in radial direction induces critical mechanical stress on a power transformer. In this paper, the radial short-circuit forces which are exerted on transformer low voltage (LV) windings are investigated. Firstly, the mechanisms of leakage flux and short-circuit electromechanical forces in transformer coils are analyzed. Afterwards, based on IEC standards followed by short-circuit tests, calculations of radial short-circuit forces and evaluations of the ability to withstand short currents in LV windings are developed. The case studies and comparisons with improved measures show that the evaluation and calculation method is feasible and effective, and this method also offers three useful ways to strengthen the ability to withstand short-circuit currents for transformer windings.

Abstract: The ZB1 cup-type steel tubular tower is the first single-circuit tower for UHV transmission line in heavy icing area. Except the ground supports, steel tubular are applied in whole tower. The plug-in boards and forging flanges are used in ZB1 tower,and the highest strength of tubular steel is Q345. Through the monographic study on the tower optimizationnode structuretowers Eiffel effect and bending moment at member end et., The design of ZB1 cup-type steel tubular tower is improved. The success of full-scale test verified the reliability in design and manufacture of cup-type steel tubular tower for UHV in heavy icing area. Research results of this paper can be applied in UHV transmission line projects.

Abstract: Based on Hilbert transform and complex trigonometric operation, this paper presents a new digital algorithm to improve the monitoring accuracy of the dielectric loss factor, and the theoretical basis of the algorithm is also deduced. Simulation results show that, the new algorithm renders good application performance when there exists power frequency fluctuation or the sampled data length is not exactly an integer fold of a power cycle, which demonstrates the algorithm can effectively solve the issues incurred from asynchronous sampling.

Abstract: In order to determine the calculational model of long span transmission tower structure under the multiple support excitation, tower-lines system are adopted. Seismic Performance of long span transmission tower lines system under Multiple Support Excitation were studied by time history analysis method. The seismic response difference of two kinds of excitation is analyzed from Dynamic Characteristics and the number of dangerous bar. It will offer the theory data for the seismic design of the kind of structure. Through analysis, the seismic response difference of the two kinds excitation is correlative to the apparent velocity; Therefore long span transmission tower structure should be considered the effect of multiple support excitation, otherwise the conclusion will be inclined to conservative or risk. Key words: tower lines system; seismic response; time history analysis,multiple support excitation

Abstract: With the development of high voltage long distance transmission and expansion of the grid, the reactive power compensation device with excellent adjustment function becomes more and more important. This paper aims to study a high temperature superconducting magnetically controlled saturable reactor (HTS MCSR), which has a wide range of stepless reactive power capacity adjustment and little operating loss. An adjustable reactor topology of three split limbs core was proposed. Based on research of structure and theory, the operating characteristic was obtained. A normal conductive prototype was manufactured. Simulation and test were done to verify the adjustment characteristic of this reactor. The results confirm the concept and provide an experimental basis for developing HTS MCSR in the future.

Abstract: Chaos is extremely sensitive to initial conditions, which makes the system with even smaller initial amount of changes can eventually evolve into a very different result. In an indirect field-oriented control of induction motor drive when estimated errors exist, within a certain range of parameters the system may evolve into chaotic motion through period-doubling bifurcation. In this paper an adaptive controller for synchronizing two indirect field-oriented induction motor drives under chaotic state is presented. Simulation results show that with the state-error feedback controller, synchronous state may be achieved rapidly and robustly.