Advanced Materials Research Vols. 805-806

Abstract: This study is the analysis and design of a basin structure which has the ability to form a gravitational vortex stream. Such a high velocity water vortex stream can possibly be used as an alternative energy resource. In this study we are interested in the formation of a water vortex stream by gravitation, which is a new technique used in the field of hydro power engineering. The advantage of this method for electrical generation is the capability of producing energy using low heads of 0.7 to 3 meters. It can be applied in a low head micro hydro power plant. The governing equations are the Navier-Stokes equations. The SIMPLE method was adopted to solve the discretized equation. The flow fields in the flume, under different incoming flow conditions and basin configurations, were numerically simulated using the software ANSYS Fluent. The studies investigated parameters which affect the velocity vector flow field, which include 1) Outlet diameter at the bottom center of basin 2) Gravitational vortex head and 3) Flow rate. Computational fluid dynamics is used to simulate the vector flow field. The tangential and radial velocity distribution is used to determine the suitable turbine blade for testing. A gravitational vortex power plant model is created to investigate electrical power output.

Abstract: Taking the typical electromagnetic voltage transformer JDCF-110 as the research object, according to the performance characteristics, the optimization mathematical model is set up. Ant colony algorithm is selected as optimization algorithm. With the cost as objective function, the settings of key parameters are studied on in optimization design. By use of Visual C++ language, the optimization design software of electromagnetic voltage transformer is finished on the plat of Windows XP. According to users requirement, the basic design and the optimized design of electromagnetic voltage transformer can be conveniently and quickly realized.

Abstract: Component outage model plays an important role in risk assessment of the power grid safety. In this paper, three aspects resulting in failures were taken into consideration, which are: repairable failure, aging factor, and the weather dependent factor. Repairable failure model can be obtained based on statistical date in the past, while aging failure model were simulated according to normal distributions. Moreover, the weather dependent characteristics of both models were combined, and ultimately, it was possible to derive the components outage probability model. Besides, the feasibility of this model was proved by an actual line in the IEEE-RTS96.

Abstract: The technology of secondary equipment condition diagnosis and failure functional recovery could improve security, stability and effectiveness in smart substation. The development of status diagnosis and trends is summarized , and outstanding issues are discussed. The program of state diagnosis and failure function recovery are proposed on the basis of exiting technology; diagnosis model based on IEC 61850network device discovery and failure function recovery, etc are mainly studied. The smart substation secondary equipment diagnostic and failure function recovery are explored, which meets the development of mart grid self-healing and self-control.

Abstract: Based on traditional complementary power supply system, the actual wind-PV-diesel hybrid energy supply system comprising three energy sources, namely PV, wind and diesel generations based on dc bus is established. Each of the three energy sources is controlled so as to deliver energy at optimum efficiency. Then the designing and computing modeling of distributed sources such as wind turbines, photovoltaic array and battery is proposed. Models of wind turbines, photovoltaic array and characteristics of the battery, respectively established the mathematical model of them, and then the simulation model is respectively built by PSCAD/EMTDC. So a micro-network experiment and simulation platform is established, which can simulate any power of wind and solar power output characteristics.

Abstract: This paper presents a new methodology for power cable monitoring. The methodology makes the transient voltage and current of the power cable as the source; decomposing the transient voltage and current to the harmonic sequence, then the defecting insulation identification function can be built. Calculating the distribution of the identification function in harmonics and the frequency characteristics of the equivalent insulation resistance , the power cable insulation defects monitoring and diagnosis can be achieved. Only the existing monitoring system hardware without external source can be used by the method ology mentioned, the cable insulation defects can be monitored simply and practically. The methodology is benefit for Power cable insulation defects contribute to the development of monitoring cable insulation defects technology.

Abstract: GIS is an important part in power system. The operating status of GIS is closely related to the operation of stability and security for grid. For existing problems in GIS insulation defects of mainstream identification method, a new identification method of GIS insulation defects based on ARMA is put forward in this paper. The paper proposes a method of multi-cycle time-domain average data preprocessing, a construction method of identifying reference data, a diagnosis method of regarding the coefficient of a certain order ARMA model as comparative quantity. At the same time, the author of the paper conduct a test on new identification method using laboratory devices, and confirms data validation of new identification method. The result suggests that the new identification method is effective and reliable.

Abstract: Lightning impulse test for power transformer is a highly theoretical and empirical analysis tests for insulation assessment attaches great importance to the power transformer. Facing the problems of detection and diagnostic method based on lightning impulse test for power transformers, this paper proposes a new method of diagnosing the winding insulation defects using two groups of voltage and current with the half-wave and full-wave. This method treats parts of the lightning impulse voltage and current as the signal source, constructs recognition criterion which is closely related to the voltage and current, and diagnose transformer winding insulation defects. Whether the insulation damage exists in the transformer winding which has passed the lightning impulse test can also be diagnosed by the method.

Abstract: This work describes the field testing process of Global Navigation Satellite System (GNSS) receiver under 220KV, 500KV UHV transmission line and standard calibration field. Analysis for GNSS data results shows that the radio interference generated by EHV transmission lines have no effect on GNSS receiver internal noise levels and valid GNSS observation rate. Within 50 meters of the EHV transmission lines, the multi-path effects (mp1 and mp2 value) significantly exceeded the normal range and becomes larger with the increase of the voltage .outside 50 meters of the EHV transmission line, the multi-path effects have almost no effect on the high-precision GNSS observations.

Abstract: This paper has studied the effect of lightning oscillatory wave on transformer winding insulation fault and finds that lightning oscillatory wave can not directly cause the breakdown of turn-to-turn insulation. Even 200 times lightning oscillatory wave applied on turn-to-turn insulation, the breakdown voltage of turn-to-turn winding almost does not change. On the basis of analysis and research about the distribution and function of lightning oscillatory wave, this paper presents that lightning oscillatory wave does not directly cause the breakdown of turn-to-turn insulation, but acts on turn-to-turn insulation in the form of strong electromagnetic force. Due to the vibration and deformation of the winding, it will cause damage to the insulation and lead to inter-turn short circuit or insulation breakdown. Lightning oscillatory wave also has cumulative effect on transformer winding inter-turn insulation.