Joong-Moon Kim

A new algorithm to locate power-quality event source with improved realization of distributed monitoring scheme

This paper presents a systematic algorithm to locate the power-quality (PQ) event source in the distributed monitoring system. Firstly, this paper proposes an improved realization of a distributed monitoring scheme for PQ diagnosis. The algorithm utilizes the topology of power system and the direction of PQ events. As a result, the coverage matrix and the direction matrix are constructed. The algorithm determines the candidate areas for an event source by manipulating these two matrices. For more accurate results, it calculates the distance from the PQ monitor to the location of the PQ event source. It is explained with an illustrative example and is applied to IEEE test feeder in order to validate the accuracy. The proposed algorithm can replace the experts analysis on the PQ event source with an automated computer program.

Development of power quality monitoring system with central processing scheme

Power quality monitoring system is the cornerstone of power quality analysis, diagnosis and improvement. Power quality (PQ) measurement concepts are evolving from instantaneous metering to continuous monitoring and developments in measurement technology make PQ monitoring system more powerful. That is, now it is possible to construct a more flexible, reliable, fast and economical PQ monitoring system. This paper presents an improved PQ monitoring system with central processing scheme. The proposed system basically consists of one PQ analyzer and multiple PQ meters. PQ meter only acts as raw data acquisition system and PQ analyzer performs all calculations and analysis algorithm. The proposed system is very economical especially for large-scale system because the price of PQ meter can be dramatically lowered in this scheme. PQ monitoring algorithms to catch steady-state trends and to detect PQ events are also proposed. The prototype of this system is constructed and real-time tests are performed using this system.

Development of power quality diagnosis system for power quality improvement

This paper represents the structure and functions of total power quality data management system including power quality monitoring system (PQMS), GUI system, and PQ diagnosis system. PQMS characterizes RMS value, harmonics, and frequency, and detects power quality (PQ) events. GUI system manages and stores power quality data received from a number of PQMSs and displays the power quality trends and events. PQ diagnosis system gives total solution of power quality problems such as statistical analysis, event prediction, power quality indexing, event identification, remedy suggestion, etc. Therefore, users can improve their power quality level according to advices provided by PQ diagnosis system. This paper explains the functions of PQ diagnosis system in detail. Moreover, a prototype of PQ diagnosis system as well as PQMS and GUI system is constructed and tested.

A new definition of voltage sag duration considering the voltage tolerance curve

This paper presents a new definition of voltage sag duration which takes into consideration of the voltage tolerance characteristics of individual electrical equipment. The magnitude and the duration of voltage sag are important parameters which characterize the voltage sag event. The conventional voltage sag characterizing method can overestimate the voltage sag in case of non-rectangular sag. Furthermore, it does not take the voltage tolerance characteristics of each equipment into account. Therefore the proposed method in this paper utilizes the minimum voltage (V/sub min/) of voltage tolerance curve of each equipment. The voltage sag profile is approximated with the k/sup th/ radical root function and the effective duration is newly defined considering the voltage tolerance characteristics. The new voltage sag duration is applied to the non-rectangular sag originated from induction motor starting and compared to the maximum time(t/sub max/) to determine whether the voltage sag event can affect the equipment or not.

Development of Power Quality Management System with Power Quality Diagnosis Functions

Recently, in accordance with the development of IT technology, it is prevalent for power quality monitors to be connected to each other via networks and share their data because such networks provide system-wide insights to customers concerning power quality. Those systems can alarm and display power quality events for the convenience of customers. However, if a power quality event occurs, it is difficult for customers to determine its cause and solution because the systems do not provide appropriate power quality diagnosis functions. The power quality management system presented in this paper has been developed to provide customers with various power quality diagnosis functions so that they can cope well with power quality problems with the right measure in the right place. This paper presents the structure and functions of the developed power quality management system and shows some results of the power diagnosis functions.

Development of FACTS operation technology to the KEPCO power network-development of education program for 80 MVA UPFC operator

KEPRI has been working on a 80 MVA UPFC pilot plant (PP) project to be applied to the 154 kV system with a consortium formed with Hyosung Corporation and Siemens since April, 2000. KEPRI, the research institute of Korean Electric Power Corporation (KEPCO), has been studying the operation strategy for KEPCO 80 MVA UPFC. This paper introduces the results of on-line emulator development for the operator education at the KEPCO UPFC site.

Kinematics of cable creepage

Power cables laid in underground ducts may experience movement in the direction of dominant traffic flow. This phenomenon, so-called cable creepage, has been known for a long time but its mechanism has not been clearly understood yet. In this paper, an exact mechanism of creepage phenomenon is proposed in which cable creepage is interpreted as an accumulation of relative frictional slip developed in the process of kinematic interaction between the flexible cable and the duct which experiences deformation propagating into the vehicle traffic direction. This kinematic interaction is formulated as frictional contact problem and an appropriate analysis method is developed. It is confirmed from the calculated results that creepage can occur according to the proposed mechanism.

A Modified Voltage SAG Duration for Power Quality Diagnosis

Abstract This paper newly defines a voltage sag duration considering the voltage tolerance characteristics of individual electrical device for power quality (PQ) diagnosis. In PQ diagnosis, the magnitude and the duration of voltage sag are important parameters that characterize the voltage sag event. The conventional sag characterizing method has the possibility to overestimate the voltage sag. Furthermore it cannot take the characteristics of each device into account. The proposed method utilizes the minimum voltage of voltage tolerance curve. The voltage sag profile is approximated and the modified duration is newly defined considering the voltage tolerance characteristics. The proposed method is applied to the non-rectangular sag originated from induction motor starting and proved to be effective for PQ diagnosis. The modified voltage sag duration can be applied to stochastic analysis of PQ diagnosis and will give more realistic understanding to the customers.

A study on an AVR parameter tuning method using real-time simulator

AVR parameter tuning for voltage control of power system generators has generally been performed with the analytic methods and the simulation methods, which mostly depend on simplified off-line linear mathematical models of the power system. However, due to the nonlinear nature of the power system, such a tuned parameter may not be appropriate for all operating conditions. This paper presents an AVR parameter tuning method using a parameter optimization technique with real-time power system simulator. As this method utilizes on-line operating data, it can overcome the limitation of model uncertainty problems in the conventional method, and it can estimate the AVR parameter set which gives superior generator performance at various loading conditions. For verification, a scaled model excitation system is connected to the real-time power system simulator, and the performance of the proposed estimation method is proved.