Advanced Materials Research Vols. 860-863

Abstract: With the rapid advance of the urbanization process, the majority of cities come into the size of millions or more population. Therefore, the urban distribution network are becoming complex increasingly accordingly.How to meet the needs of complex urban distribution network safety and reliable power supply quality, reasonable construction investment better is one of the problems that plagued powered enterprise.It is an important research topic that wiring mode are choosed with good indicator of safe and high reliability, power supply quality and reasonable construction investment, combination load density characteristics of different medium-sized cities in the electricity sector. We have constructed a wiring mode analysis platform in this paper, it can calculate various operation indicators in different wiring mode by load density as the basic parameter variables.The adaptability of different wiring mode can be assessed comprehensively, and the optimal distribution network connection mode is selected in the different load density.

Abstract: GIS is the key equipment in power grid and partial discharge is the main cause leading to insulation breakdown. UHF detection is an effective method for PD detection in GIS. The insulator has great influence to the electromagnetic wave propagation in GIS. The FDTD simulation model of GIS is setup to study the influence of insulator to electromagnetic wave propagation. The amplitude and energy distribution at GIS model with and without insulator are study in this paper.

Abstract: Transfer functions of power transformer can be used for detection and localization of partial discharges. There is no access to sectional windings when transformer insulation has been impregnated into oil, so the parameter identification of transformer windings is difficult without the knowledge of sectional winding voltages. In this paper, genetic algorithms (GAs) based approach are proposed to identify the parameters of transformer windings. An impulse signal was injected into the bushings of transformer, then the responses at neutral terminals were measured, and thee acquired data were used to identify the parameters using GAs. To accelerate GAs’ convergence, a zooming operator was introduced in genetic programming process. The experimental results show that the proposed ZGA approach is effective.

Abstract: The assessment of the overload capacity of transformer has a certain practical significance. In this paper, a temperature reverse extrapolation method is proposed to assess the overload capacity of transformer. Firstly, the top oil temperature is monitored by the online monitoring system. Secondly, the temperature distribution model and the calculation methods of hot spot temperature in the PTP7 (Power Transformers. Part 7: Loading guide for oil-immersed power transformers) guide are analyzed. Then, a new method called temperature reverse extrapolation which can calculate the overload factor of transformer is composed. And based on the overload factor, two meaningful data about overload capacity are obtained. Finally, an assessment system of transformer overload capacity based on the online monitoring is developed.

Abstract: For fast and accurately assessing the risk of the transformer failure and getting the reliability of transformer components, it is proposed a new method based on Fault Tree Analysis (FTA) and Improved Fuzzy Analytic Hierarchy Process (IFAHP) in this paper. Firstly power transformer fault tree is established accordingly to make the complex transformer faults system subdivide into various kinds of basic types directly; Secondly, the IFAHP is designed to analyze the fault tree, so the complex system of transformer can be quantitatively described and the fuzzy judgment matrix can be established; Finally, the fuzzy consistent qualification is changed into a mathematical programming problem and Genetic Algorithms (GA) is adopted to get the solution so as to obtain the reliability of transformer components. In addition, the application result shows the effectiveness of the method above.

Abstract: Longitudinal ultrasonic wave signals, transverse ultrasonic wave signals and other ultrasonic body wave signals generated by partial discharge are analyzed emphatically in the acoustic emission method of partial discharge detection in high voltage equipment [1-. Velocity of longitudinal ultrasonic wave is often used to calculate partial discharge defects position in the location study of partial discharge. In practical applications errors are always large. And a recent study finds that a class of plate ultrasonic guided waves will be inspired when ultrasonic body waves are transmitted from the gaseous medium to the metal medium [9-1. As the attenuation coefficient is small and the transmission distance is large when the waves propagate along the metal plate, in the partial discharge detection, ultrasonic signals detected by the ultrasonic sensor attached to the equipment enclosure include ultrasonic guided waves besides the ultrasonic body waves.

Abstract: Partial discharges in power cables will generate small currents with low frequencies in the ground cords. In cable PD online monitoring systems, CTs are usually used to obtain such PD signals. In this paper, by derivations based on theories of wave propagation, the frequency characteristics of Rogowski CTs (RCTs) and the effects of transformer parameters (size, core material, etc.) on its pass band B, sensitivity H(jω₀), the lower cutoff frequency f_L is acquired. The feasibility of such derivations is verified by experiments. By conducting comparative experiments, the effect of the use of screening box and the way of coil winding on the performance of a current transformer is acquired. A feasible plan to improve the frequency characteristics of CTs is presented, in order to acquire more stable gain and better anti-interference ability within their pass band.

Abstract: This paper proposes a Improved positioning algorithm of electrical partial discharge applied for substations. This algorithm is based on received signal strength indication, and taken practical condition of sensors into consideration by replenishing beacon nodes. Compared with traditional trilateral weighting positioning algorithm, this paper introduces indefinite amount of localization perpendicular lines and combined them with trilateral districts to calculate the weighting result, which can reduce error. This model meets the requirement of reality that the height of electrical discharge spots differentiate from the height of the plane formed by beacon nodes (signal sensors). The experimental result indicates that the revised position model proposed by this paper can effectively fit the condition of monitoring hardware. Error of this algorithm is less than that of traditional trilateral localization.

Abstract: Abstract. In order to accurately analyze the field test results of the partial discharge in GIS and study on the partial discharge characteristics of typical insulation defects in GIS, this paper constructs a set of failure simulation test system which is based on the entity 363kV GIS which contains all the Main equipments. These system has artificial defect setting units and can applied voltage and current at the same time, it also can manually set a variety of GIS typical insulation defects at the defect setting units. The partial discharge detection and analysis in the case of the applied voltage and current can simulate actual field operating conditions of GIS.

Abstract: Abstract. Once the GIS appears screws loose and other phenomena, it will lead to the generation of floating potential, then trigger the floating potential discharge. In order to study the discharge characteristics of the floating potential, this paper artificially built floating potential defects on the GIS malfunction simulation platform, and detected with ultrasound and UHF methods. The results show that once the floating potential discharged, it would produce a larger amplitude signal. And the discharge most concentrated between the zero crossing and the peak point among the entire phase range. Ultrasound and UHF detection has obvious signal.