This paper presents a framework for fault classification using discrete wavelet transform (DWT) to prepare the feature which would be given as the input to the radial basis function neural network (RBFNN) which has high performance level especially in classification problems. The simulated network carried out using MATLAB/SIMULINK software package for three phase transmission lines which including the series compensator as it is very challenging task in line protection and other online decisions using different ten fault types, different locations along the transmission line and with different fault inception angle. Discrete wavelet energy calculated from quarter cycle of only sending post fault current signals side is used as an input to single RBFNN which is trained and tested to provide all fault types. The method responses very fast with few numbers of training samples and can also detect the ground fault cases as good as other phases without any additional data.
In service restoration against a fault in distribution system, estimation of load flow is needed to avoid overloading of feeder and voltage violation; this has been performed based on the load flow before the fault occurrence. However, in the distribution system with a number of photovoltaic generation systems (PVs), the load flows during the service restoration varies from ones before the fault occurrence due to the disconnection of PVs. Therefore, it is important to estimate the magnitude of actual load accurately before the fault occurrence. This paper proposes the method to estimate the actual load and PV power output online from the power flow data measured before the fault occurrence. The proposed method consists of two processes. The first process is tentative load and PV power estimation by means of the Independent Component Analysis with heuristic knowledge on PV power factor. Second process is correction of tentative estimation values based on the recurrence formula. The validity of proposed method is investigated through some computational simulations.
For the suppression of metallic particle lift-off in compact Gas-Insulated-Switchgear (GIS), a coating with nonlinear resistivity characteristic was adapted to the inner surface of GIS tank. Electrical field analysis using the measured current density to electric field (J-E) characteristics indicates that the nonlinear resistivity coating can reduce the field enhancement between metallic particles and the coating effectively to suppress particle lift-off. Experiments using a coaxial GIS bus duct geometry indicate that the nonlinear resistivity coating increases the lift-off electric field of metallic particles with small statistical dispersion compared to a dielectric coating.
When a fault arc occurs in oil-filled electric equipment such as transformers in transmission and distribution systems, it generates a flammable gas and a dynamic pressure rise that may trigger an explosion. This paper describes a fundamental study concerning pressure rise due to an underwater arc in a closed vessel containing of air and water prior to examination of the arc phenomena in the electrical insulating oil. In this study, the pressure rises in both air and water are measured under experimental conditions of an arc current ranging from 0.5 to 6.7kA and an arc duration of 10 or 20ms. Experimental results show that the behavior of a bubble generated by the underwater arc affects the pressure rise in the air and the water as low-frequency pressure oscillation comparatively. Additionally, in water, two pressure-peaks are observed as high-frequency pulses. The first pressure peak is observed at almost the same time as the arc is ignited, while the second is produced when the bubble collapses due to vapor condensation.
This paper investigates a mutual grounding impedance between vertical grounding electrodes based on field measurements and FDTD simulations. In the case of vertical electrodes, the mutual impedance between the electrodes is almost independent of the electrode length, and thus an induced voltage is nearly constant as the electrode length becomes longer. This characteristic is different from that of an overhead conductor where the electromagnetic induced voltage is proportional to the conductor length. The greater the separation distance between the electrodes, the smaller the induced voltage same as that of the overhead conductor. The propagation velocity increases as the separation increases. It is found that the velocity is not necessarily proportional to the inverse of the relative permittivity of the earth.
The design method of hydrogen electricity storage system is presented. The various electricity storage requirements are classified to 3 steps, according to the amount of renewable energy introduction. The hydrogen electricity storage system is the most cost effective in the step 3, where renewable energy is introduced as a main power source. Then DC link wind power and alkaline electrolysis hydrogen production cooperating system design and its control system with small battery to suppress the renewable energy output fluctuations is presented.
Experimental study for the lightning impulse V-t characteristics of the anti-pollution-type distribution insulator under dry and polluted conditions was carried out to establish insulation coordination throughout the power distribution system. This paper proposes an approximate formula having three independent variables and evaluates the parameters to calculate the V-t characteristics. Many experimental data fit with the proposed approximate formula for various conditions.
The Editorial Committee is working in planning and editing of the publication of Power and Energy Society. In this article, activities of the committee of the last term are reported, and recent trend and future problems are also discussed. The process of planning and editing of the publication, and the challenges to reduce the necessary months for reviewing papers and to increase the number of submitted papers are shown.