김철환

This tutorial gives an introduction to the field of the wavelet transform. It is the first of two tutorials which are intended for engineers applying or considering to apply WTs to power systems. They show how the WT-a powerful new mathematical tool-can be employed as a fast and very effective means of analysing power system transient waveforms, as an alternative to the traditional Fourier transform. The focus of the tutorials is to present concepts of wavelet analysis and to demonstrate the app

Site-directed mutagenesis and gene-replacement procedures were used to isolate mutant strains of Azotobacter vinelandii that produce altered MoFe proteins in which the alpha-subunit residue-195 position, normally occupied by a histidine residue, was individually substituted by a variety of other amino acids. Structural studies have revealed that this histidine residue is associated with the FeMo-cofactor binding domain and probably provides an NH-->S hydrogen bond to a central bridging sulfide l

A gene (yacK) encoding a putative multicopper oxidase (MCO) was cloned from Escherichia coli, and the expressed enzyme was demonstrated to exhibit phenoloxidase and ferroxidase activities. The purified protein contained six copper atoms per polypeptide chain and displayed optical and electron paramagnetic resonance (EPR) spectra consistent with the presence of type 1, type 2, and type 3 copper centers. The strong optical A(610) (E(610) = 10,890 M(-1) cm(-1)) and copper stoichiometry were taken a

This paper describes a novel fault-detection technique of high-impedance faults (HIFs) in high-voltage transmission lines using the wavelet transform. The wavelet transform (WT) has been successfully applied in many fields. The technique is based on using the absolute sum value of coefficients in multiresolution signal decomposition (MSD) based on the discrete wavelet transform (DWT). A fault indicator and fault criteria are then used to detect the HIF in the transmission line. In order to discr

This paper describes a novel fault detection technique of high impedance faults (HIFs) in high voltage transmission lines using the wavelet transform. Recently, the wavelet transform (WT) has been successfully applied in many fields. The technique is based on utilising the absolute sum value of coefficients in multiresolution signal decomposition (MSD) based on the discrete wavelet transform (DWT). A fault indicator and fault criteria are then used to detect the HIF in transmission line. In orde

This is the second in a series of two and illustrates some practical applications of the wavelet transform to power systems: protection/fault detection, detection of power quality disturbances and analysis of the partial discharge phenomenon in GIS (gas-insulated substations). Emphasis is placed on a number of practical issues.

Islanding in power systems is a challenge that results in various uncertainties in the system parameters, degrades power quality, and may endanger the maintenance workers. This study presents a new passive islanding detection approach for grid‐connected distributed generation (DG) units. The proposed method employs a Kalman filter (KF) to extract and filter the harmonic contents of the voltage signal measured at DG terminals. A three‐phase voltage signal is measured at the point of common coupli

Using the modified Wald test suggested by Toda and Yamamoto (1995 Toda, HY and Yamamoto, T. 1995. Statistical inference in vector autoregressions with possibly integrated processes. Journal of Econometrics, 66: 225–50. [Crossref], [Web of Science ®] , [Google Scholar]), the study examines whether higher budget deficits lead to greater current account deficits in Korea. This test allows one not only to examine the general validity of twin deficits hypotheses, but also to predict future Korean ext

Zone 3 of a distance relay is used to provide the remote backup protection in case of the failure of the primary protection. However, the risk of maloperation under stressed conditions such as heavy loading, voltage, and transient instability is quite high. Zone 3 is used in combination with the derivatives of the voltage and current, etc. to prevent maloperation. At times, the impedance characteristics that restrict the tripping area of relay are used to avoid maloperation due to load encroachm

The increasing penetration of electric vehicles (EVs) in the distribution grid has established them as a prospective resource for ancillary services. These services require adequate control strategies for prompt and efficient operation. In this study, an energy management scheme (EMS) has been proposed to employ an off-board EV smart charger to support the grid during short-term variance of renewables and reactive load onset. The scheme operates by calculating power references for the charger in

Microgrids experience significantly different fault currents in different operating scenarios, which make microgrid protection challenging. Existing intelligent protection schemes rely on the extraction of appropriate fault features using statistical parameters. The selection of these features is difficult in a microgrid because of its various operating scenarios. This study develops a convolutional neural network‐based intelligent fault protection strategy (CNNBIPS) for microgrids that inherent

This paper presents the implementation of a distance relaying algorithm using EMTP MODELS, in which we have simplified the procedures of system modeling and distance relaying system by using a single structure of MODELS. The technique presented is based on integrating the modeling of the power system and the protective system in one program module. The purpose of this paper is to provide systematic relaying concepts by modeling a digital relaying system using MODELS functions within EMTP in a cl