Applied Mechanics and Materials Vols. 668-669

Abstract: For double circuit lines on the same tower, traditional phase selectors for single lines can not operate correctly in crossing-line faults. To ensure the performance of faults phase selection in the single lines and meanwhile achieve accurate phase selection in crossing-line faults, an integrated fault phase selection scheme based on fault component current is proposed. Firstly, faults are divided into single lines faults, same-name-phase crossing-line faults and non same-name-phase crossing-line faults, then the phase selection is classified. The process with adaptive capacity can automatically select the suitable phase selector not affected by fault types. Simulation results via PSCAD/EMTDC show that the phase selection scheme based on fault component current has good performances for different fault types, fault location and transition resistance.

Abstract: This paper mainly introduces the system configuration of the Philippines Mariveles power plant, the difficulty and key points of the unit fast cut load (Fast Cut Back - FCB) control function were analyzed, and the boiler pressure control valve (Pressure Controlling Valve - PCV) discharge, turbine bypass opening coordination decrease pressure, integrate the override control, a fixed value servo and other control strategy, the possible problems in the process of test are sorting and analysis, and put forward effective solution, ensure the successful application of turbine outages kept boiler of FCB function, lay solid foundation for the safe and stable operation of the power grid.

Abstract: Nowadays, with the rapid development of industrial technology especially the power electronic technology, harmonic and reactive power problems are becoming severer. In sinusoidal conditions, there are no controversies on the definition of power quantities. In nonsinusoidal circuits, the traditional definition of active power is still applicable while the definitions of reactive power and apparent power are in controversy. Based on an optimization current decomposing method, this paper derives the expressions of optimal current and compensating current in a single-phase and a three-phase circuit by constructing a Lagrange functions. Based on simulation studies, the compensating effect of the optimization method is analyzed and shown; it can noticeably improve the efficiency of energy transfer in circuit. The paper presents all mathematical derivation of the method and verifies the results based on simulation.

Abstract: In dynamic operating environment, it is one of key issues in the research field of electric energy metering that the accuracy of synchronous sampling signal based on phase locked technology. Because operating environment changes from steady state to dynamic, analytical description of PLL input signal becomes an urgent problem to be solved. In this paper, dynamic signal is analyzed mathematically by using zero-crossing detection theory, its phase expression is obtained, then mathematical equivalent conversion is made based on operation characteristics of PLL, its phase input equation is obtained, finally the correctness of the input equation is verified by Fourier transform method. This study lays the foundation for error analysis of electric energy metering system under dynamic condition.

Abstract: The traditional electric power metering theory is a kind of no-error metering theory in sinusoidal steady-state circuit. However, the applying condition is too rigor, and the engineering environment is hard to fulfil, the application premise should be extended to dynamic. Ideal linear elements are adopted to build a first-order dynamic circuit. And the analytic expressions of the capacitor cumulative electric energy in the charging process are derived theoretically. It points out that the cumulative electric energy of capacitor in dynamic circuit is a nonzero value. This fully demonstrates that the energy metering principle brings error when it is used in dynamic environment.

Abstract: Based on the background of compressed air energy storage system (CAES), this paper analyzes hybrid compression energy storage system (HCES) firstly. Design a new type of energy storage system - cyclic compression energy storage system (CCES). Secondly, study its working principle and characteristic parameters, such as compression-release efficiency, energy density and so on. Finally, by simulation and parameter calculation, prove the correctness of the theoretical analysis.

Abstract: A kind of 10KV power distribution network fault indicator integrating measurement and communication functions was researched and developed. Used in 10KV power distribution overhead lines, this indicator is also designed with the communication module, current and temperature measurement module in addition to having the function of plate turning indication in case of grounding or short circuit fault. Through a wireless communication mode, the fault or measurement information is sent to the nearby data terminal unit, which sends the data to the monitoring center through the GPRS network. Workers will know the working status of the whole power distribution network in a real-time manner through the computer of the monitoring center. By adopting the ATmega8L MCU as the core, the new type of fault indicator realizes the wireless data transmission function through NRF24L01.

Abstract: With phasor measurement units (PMU) become available in the distribution system; the estimation accuracy of the distribution system state estimation (DSSE) is expected to be improved. Based on the weighted least square (WLS) approach, this paper proposed a new state estimator which takes into account the PMU measurements including voltage magnitude and phasor angle, and load current magnitude and phasor angle. Simulation results indicate that the estimation accuracy is obvious improve by adding PMU measurements to the DSSE. Furthermore, the estimation accuracy changes with the installation site of PMU, and can be maximized by choosing the installation site appropriately.

Abstract: How to eliminate the influence of network storm produced by GOOSE messages on equipment of process level is an important task to smart substation. Both valid and invalid GOOSE messages transmitted in process levelare likely to lead to the network storm. At first, the reason that causes network storm in smart substation is analyzed in this paper. Then three kinds of filtering methods are given: Real-time matching method with creating a buffer, the method of cutting off the storm network and abnormal packets discarded method, In the end, the first method is verified on the intelligent terminal.

Abstract: This paper describes the influences of transmission line on the safety and reliability of grid, and illustrates the necessary of visual management of transmission lines. Virtual 3d scene modeling method is introduced in detail, including Virtual 3d scene modeling and virtual 3d entity modeling. According to the characteristics of transmission line, the 3d scene of transmission line ia designed and implemented. At last, Virtual reality modeling language (VRML) is used to complete the optimization of the established model and the experimental results show that the data size of the optimized model has reduced considerably.