Sang-Min Yeo

A novel algorithm for fault classification in transmission lines using a combined adaptive network and fuzzy inference system

Accurate detection and classification of faults on transmission lines is vitally important. In this respect, many different types of faults occur, inter alia low impedance faults (LIF) and high impedance faults (HIF). The latter in particular pose difficulties for the commonly employed conventional overcurrent and distance relays, and if not detected, can cause damage to expensive equipment, threaten life and cause fire hazards. Although HIFs are far less common than LIFs, it is imperative that any protection device should be able to satisfactorily deal with both HIFs and LIFs. Because of the randomness and asymmetric characteristics of HIFs, the modelling of HIF is difficult and many papers relating to various HIF models have been published. In this paper, the model of HIFs in transmission lines is accomplished using the characteristics of a ZnO arrester, which is then implemented within the overall transmission system model based on the electromagnetic transients programme. This paper proposes an algorithm for fault detection and classification for both LIFs and HIFs using Adaptive Network-based Fuzzy Inference System (ANFIS). The inputs into ANFIS are current signals only based on Root-Mean-Square values of three-phase currents and zero sequence current. The performance of the proposed algorithm is tested on a typical 154 kV Korean transmission line system under various fault conditions. Test results show that the ANFIS can detect and classify faults including (LIFs and HIFs) accurately within half a cycle.

Analysis of Transient Overvoltages within a 345kV Korean Thermal Plant

This paper presents the simulation results for the analysis of a lightning surge, switching transients and very fast transients within a thermal plant. The modeling of gas insulated substations (GIS) makes use of electrical equivalent circuits that are composed of lumped elements and distributed parameter lines. The system model also includes some generators, transformers, and low voltage circuits such as 24V DC rectifiers and control circuits. This paper shows the simulation results, via EMTP (Electro-Magnetic Transients Program), for three overvoltage types, such as transient overvoltages, switching transients, very fast transients and a lightning surge.

Algorithm for Fault Location Estimation on Transmission Lines using Second-order Difference of a Positive Sequence Current Phasor

The accurate estimation of a fault location is desired in distance protection schemes for transmission lines in order to selectively deactivate a faulted line. However, a typical method to estimate a fault location by calculating impedances with voltages and currents at relaying points may have errors due to various factors such as the mutual impedances of lines, fault impedances, or effects of parallel circuits. The proposed algorithm in this paper begins by extracting the fundamental phasor of the positive sequence currents from the three phase currents. The second-order difference of the phasor is then calculated based on the fundamental phasor of positive sequence currents. The traveling times of the waves generated by a fault are derived from the second-order difference of the phasor. Finally, the distance from the relaying point to the fault is estimated using the traveling times. To analyze the performance of the algorithm, a power system with EHV(Extra High Voltage) untransposed double-circuit transmission lines is modeled and simulated under various fault conditions, such as several fault types, fault locations, and fault inception angles. The results of the simulations show that the proposed algorithm has the capability to estimate the fault locations with high speed and accuracy.

Analysis of System Impact of the Distributed Generation Using EMTP With Particular Reference to Protection Strategies

Abstract With the advent of distributed generation, the overall power system are impacted on stability and power quality. The distributed generation has a positive impact on system restoration following a fault, higher reliability, and mitigation of effect due to voltage sag. However, the distributed generation also has a negative impact on decrease of reliability such as changes of protective device setting and mal-operation. Because bulk power systems consist of various sources and loads, it is complicated to analyze power system with distributed generation. The types of distributed generation usually are classified both rotating machinery and inverter-based system. In this paper, the distributed generation is designed by synchronous generator, and the distribution system with model of the distributed generation is simulated using EMTP. In addition, this paper shows the simulation results according to the types of distributed generation.

The modeling of over-current reclosing relay using dynamic link library

This paper presents a new method of modeling using a Dynamic Link Library (DLL) function in the Electro-Magnetic Transients Program — Restructured Version (EMTP-RV), in which we have simplified the procedures of over-current reclosing relay modeling. The EMTP-RV is the enhanced computational engine. and EMTPWorks is a new Graphical User Interface (GUI) of EMTP. The major improvements to EMTP-RV are a new approach with built-in models and encapsulation, user-defined modeling, and a code structure designed to be expandable to specialized toolboxes using the DLL function. The DLL function is designed to allow EMTP-RV users to develop advanced program modules and interface them directly and intimately with the EMTP-RV engine. The modeled over current reclosing relay is verified by simulating the various types of faults in the distribution system. The results show the validity of the over current reclosing relay model.

Modeling and analysis of Photo-Voltaic system using EMTP

The installation of grid-connected Photo-Voltaic (PV) systems has recently increased due to several advantages it offers in comparison to standalone PV systems. However, power quality deteriorates when a PV system is connected to grid. Therefore, the analysis of grid-connected PV systems is required due to the increase in power quality problems when PV systems are connected to the grid. Electromagnetic Transients Program Restructured Version (EMTP-RV) is the enhanced computational engine and EMTP Works is its new Graphical User Interface (GUI). The major improvements of EMTP-RV include a new approach using built-in models and encapsulation, user-defined modeling, and code structure that is designed to be expandable to specialized toolboxes using the Dynamic Link Library (DLL). The authors use two methods for the modeling of PV systems. The first method is the modeling done by the built-in components and the second is the modeling done by the DLL. In this paper, we describe the modeling and analysis of grid-connected PV systems via EMTP-RV. The modeled PV systems are compared with actual data and are verified under various conditions.

Analysis of System Impact of the Distributed Generation Using EMTP With Particular Reference to Voltage Sag

Abstract With the advent of distributed generation, the overall power system are impacted on stability and power quality. The distributed generation has a positive impact on system restoration following a fault, higher reliability, and mitigation of effect due to voltage sag. However, the distributed generation also has a negative impact on decrease ofreliability such as changes of protective device setting and mal-operation. Because bulk power systems consist of various sources and loads, it is complicated to analyze power system with distributed generation. The types of distributed generation usually are classified both rotating machinery and inverter-based system. In this paper, the distributed generation is designed by rotating machinery, and the distributed system with model ofthe distributed generation is simulated using EMTP . In addition, this paper shows the simulation results according to the types of distributedgeneration.