Advanced Materials Research Vols. 1070-1072

Abstract: Power systems as 10kV, 35kV and etc have a lot of high-voltage three-phase three-element combined transformer. At present, all of the combined transformers are verified according to single-phase verification method, but the results can’t reflect the true error characteristics of combined transformer. So, it is suggested to adopt three-phase verification method to verify combined transformer. However, when combined transformer is verified according to three-phase verification method, it has not been clear yet that what influence magnetic field generated by current has on voltage error. In this paper, through voltage error test on combined transformer with three-phase verification method at different current, it is discovered that magnetic field has a larger influence on voltage error in the presence of a magnetic field, with the increase of voltage, the influence of magnetic field on voltage error decreased gradually from larger values. The use of three-phase verification method and appropriate modification of current error limits are recommended when combined transformer is verified.

Abstract: In order to improve the dynamic performance, based on the analysis of the dynamic model of doubly fed induction generator (DFIG), this paper presents an improved direct power control strategy which is based on the direct control of stator active and reactive power of DFIG. The proposed method only utilizes the estimated stator flux by the stator resistance which is the only machine parameter, so as to remove the power dithering resulting from the inaccuracy associated with rotor flux estimation. In the Matlab/Simulink, simulation results for a 15KW DFIG system demonstrate the high accuracy and excellent dynamic performance during variations of active and reactive power, and revolution.

Abstract: In order to improve the dynamic performance of three-phase voltage type PWM rectifiers predictive direct capacitor power control, in view of the deficiencies of slow response and poor dynamic performance of present PI control of load disturbance, the fractional order PID controller of the DC side voltage control section is introduced to the capacitive power control. The new predictive direct power capacitor control strategy has been proposed. It consists of two parts: the outer loop of voltage square model of fractional order PID and the inner loop of capacitor power and the reactive power in network side. Through decoupling control with the prediction control of the inner loop and the voltage outer loop of fractional PID, the dynamic performance of a direct power control has been improved. The Matlab/Simulink simulation results prove that the system has better dynamic performance, robustness and response speed of direct power control.

Abstract: The paper introduces field test on critical process parameters regarding stringing construction of 1250mm² large-section conductor to know the effect of change in single factor among critical construction process parameters such as conductor stringing tension, envelop angle of conductor on paying-off tackles, times of conductor to pass over paying-off tackles, etc. in tension stringing process on conductor damage, analyzes test data and comes to the initial conclusion of effect exerted by tensioning parameters on conductor damage by citing the example of change in stringing tension.

Abstract: The paper introduces project test tensioning of 1250mm² large-section conductor and validate structural stability and tensioning characteristics of newly developed 1250mm² large-section aluminum stranded conductor, reasonability of construction processes and critical construction parameters and applicability of newly developed construction machines and tools to the conductor.

Abstract: Both the cost-effective operation of power systems and reliable operation are inextricably linked with the transformer life assessment. This paper analyzes the composition of the transformer life, life assessment factors and existing assessment methods. Based on factors of the current life assessment and problems of assessment methods, the paper analyzed the importance significance of uncertainty in the transformer life assessment and proposed the transformer remaining life assessment model, and methods based the random fuzzy theory. Assessment results can provide the basis for the transformer maintenance and help safe and economic operation of power systems.

Abstract: For high-altitude environment particularity, the device was designed for high-altitude correction. The equivalent stress analysis of particle system is researched to meet seismic requirementsneeds of automotive mobile devices. A new auto-switch is designed by improving the traditional tap-switch for automatic switching cable in the car. It is first used in a car as a automatically switch and greatly reduces the manual wiring workload. The field test results show that the device can assume a high altitude solar motion detector demand of the low voltage ride through (LVRT) .

Abstract: UHF electromagnetic waves radiated by PD in GIS can range from several hundreds of MHz to several GHz. FDTD method is usually used to simulate the characteristics of the UHF electromagnetic waves. Compared with the traditional ideal Gaussian pulses in simulation, one equivalent PD mathematical model based on the actual measure PD sources was considered to simulate the propagation characteristics. Time domain and frequency domain spectrum of signals excited by the two PD sources were studied to analyze the propagation characteristics. It can draw the conclusions that each insulator detect leads to each electromagnetic and its time domain and frequency domain spectrum. So it is recommended to use equivalent PD mathematical model to simulator the propagation characteristics.

Abstract: As the main types of parallel FACTS devices, the basic function of SVC and STATCOM is to realize the dynamic compensation of reactive power and maintain system voltage stability. However, when new control strategies are added to them .Both of them can suppress SSO effectively. Based on IEEE first benchmark model, this paper established simulation model by PSCAD/EMTDC. The effects of suppressing SSO by SVC/STATCOM are verified with time domain simulation, and the comparative analyses are carried out on the effects of suppressing SSO by SVC and STATCOM.

Abstract: Many error abnormities and verification difficulties appear in high voltage transformer field error tests. Field verification is with site and duration limit, so it is important to timely solve problems and complete tests. Field practical problems and solutions are expounded through technical analysis for technicians in the presented work.