Sung-Duck Kim

An Application of Dynamic Thermal Line Rating Control System to Up-Rate the Ampacity of Overhead Transmission Lines

A method is proposed to utilize the dynamic-line rating system on old transmission lines to up-rate ampacity without replacing old conductors or increasing line voltage. A DLR system applicable to double-circuit transmission lines is designed based on maximum-allowable conductor temperature, conductor temperature at the limit-dip (sag) margin, and transformer maximum load. The improved performance of the system is reported.

An Improved Method for Classifying Power Quality Disturbances

An adaptive neuro-fuzzy inference classifier based on the discrete wavelet transform (DWT) to recognize the type of power quality (PQ) disturbances is presented. The DWT, using the multi-resolution signal decomposition (MSD), can transfer power disturbance characteristics into the time-frequency domain. The energy of the signal decomposed to frequency sub-bands can be used to extract feature parameters for classifying various disturbances. The proposed classifier was designed using four feature parameters that consist of energy concentration level and its mean value, mean energy of the signal, and an auxiliary parameter determined by the rms value and pulse detection. The proposed classifier shows good recognizing efficiency for ten types of PQ events, including one double event disturbance.

Mechanical deterioration of ACSR conductors due to forest fires

Considerations for the remaining life of the Aluminum Stranded Conductors Steel Reinforced (ACSR) in transmission lines have become gradually important to hold the reliability and the stability of the electric power supply. The useful life of the ACSR exposed to the atmosphere for a long period may be dependent on deterioration caused by such factors as atmospheric corrosion, galvanic corrosion, crevice corrosion, or fatigue corrosion. Forest fires for any overhead transmission lines built nearly on the ridge of the mountains may significantly reduce to the mechanical strength of the ACSR and lead to failure or accident. In this paper, material and mechanical deterioration performances of ACSR due to forest fires are presented through several sample tests. Data analysis for tension load and extension of ACSR after blazed are reported.

A Design for Dynamic Line Rating System to increase Overhead Transmission Line Capacities

Dynamic Line Rating (DLR) techniques have been greatly worthy of notice for efficiently increasing transmission capacity as well as controlling load-flow in overhead transmission lines, in comparison with the existing power system operating with Static Line Rating (SLR). This paper describes an utilization method to implement DLR control system for old transmission lines built in the first stage using the ground clearance design standard with lower dips. The suggested DLR system is focused on designing as temperature control system rather than current/load control system. Based on several performance for conductor temperatures, it is shown that DLR system with efficiency can be implemented.

A An Experimental Study for Load Capacity and Dip Characteristic in Overhead Transmission Lines

Overhead transmission lines in domestic area have been built by several different design standards of dip and ground clearance. This paper describes an experimental study for evaluating load capacity and dip margin in overhead transmission lines. Such design standards for selection of overhead transmission conductors, dip and ground clearance, as well as electrical equipment technical standard are discussed. Based on daily load and weather data, several characteristics such as line utilization factor, load factor, conductor temperature and dip, etc. are analyzed, and compared with the specified levels of design standards. As a result, it is verified that DLR method can be a clue of the solving of the problem, for occurring in old transmission conductors which may be rarely operating below standards.

A Reassessment for Dynamic Line Rating of Aged Overhead Transmission Lines in Kepco`s Network

During the past 2 decades, many electric power companies have been searching various solutions in order to supply power with economical and more efficiency in the present transmission utilities. Most interesting method to increase the line capacity of overhead transmission lines without constructing any new line might be to adapt Dynamic Line Rating(DLR). Specified rating is normally determined by any current level, not by conductor temperature. Although specified rating is essential to design transmission line, dip may be the most important factor in limiting transmission capacity. Transmission lines built by the oldest dip criterion among the 3 different design criteria for conductor dip are nearly over one-half of all Kepco`s transmission lines. This paper describes an up-rating method for those transmission lines in order to apply DLR technique. Based on limit dip conductor temperature and current of the transmission lines, limitation performance and effectiveness in applying DLR with weather model are analyzed. As a result of analysis, it can be shown that an improved method could be effectively used for increasing the line rating of old transmission line which was built by the design criterion with low dip margin.

An Evaluation Method for Short-Term Ratings of Double-Circuit Overhead Transmission Lines

This paper describes an analytical method to determine the short-term ratings to reliably operate the overhead transmission lines with double-circuit lines when faulting one circuit of the two. As linearizing the thermal equilibrium equation that represents the temperature characteristic of conductors, we show that the linear equation can be easily represented the over-current and it`s temperature property during overloading the one line. Generally, it is well hewn that the short-term line ratings should be determined by considering both conductor life and dip. However, most power companies have their own different guides for the short-term ratings. Using the suggested method in this paper, it can be re-accessed the short-term ratings given in Kepco`s overhead transmission lines constructed during the past three different periods. As a result, it is verified that the short-term ratings could be increased mil efficiently. Furthermore, it would be directly applied the given method to determine the short-term dynamic line ratings when occurring faults in one of the double-circuit lines, without doing my other actions for the current lines.

Short-Term Dynamic Line Rating Prediction in Overhead Transmission Lines Using Weather Forecast System

A method for predicting the short-term dynamic line ratings in overhead transmission lines using real-time weather forecast data is proposed in this paper. Through some inspections for the 3-hour interval forecasting factors such as ambient temperature, wind speed grade and weather code given by KMA(Korea Meteorological Administration), correlation properties between forecast weather data and actual measured data are analyzed. To use these variable in determining the dynamic line ratings, they are changed into suitable numerical values. Furthermore adaptive neuro-fuzzy systems to improve reliabilities for wind speed and solar heat radiation ate designed It was verified that the forecast weather data can be used to predict the line rating with reliable. As a result it can be possible that the proposed predicting system can be effectively utilized by their anticipation a short-time in advance.

An Improved Method for Fault Location based on Traveling Wave and Wavelet Transform in Overhead Transmission Lines

An improved method for detecting fault distance in overhead transmission lines is described in this paper. Based on single-ended measurement, propagation theory of traveling waves together with the wavelet transform technique is used. In estimating fault location, a simple, but fundamental method using the time difference between the two consecutive peaks of transient signals is considered; however, a new method to enhance measurement sensitivity and its accuracy is sought. The algorithm is developed based on the lattice diagram for traveling waves. Representing both the ground mode and alpha mode of traveling waves, in a lattice diagram, several relationships to enhance recognition rate or estimation accuracy for fault location can be found. For various cases with fault types, fault locations, and fault inception angles, fault resistances are examined using the proposed algorithm on a typical transmission line configuration. As a result, it is shown that the proposed system can be used effectively to detect fault distance.

Application and evaluation of short-term emergency ratings for double-circuit transmission lines

Abstract Emergency ratings have been introduced for operating transmission lines safely and supplying current capacity efficiently, as well as controlling load flow when line faults occur. In this article, short-term emergency ratings are calculated by using a thermal equilibrium equation for bared conductors in double-circuit transmission lines. Overhead transmission lines installed in double circuit have been extensively utilized worldwide to enhance power transmission. Such lines show various advantages in increasing transmission capacity and decreasing power loss as well as being operated flexibly during a contingency. Even when a fault occurs in one circuit, the healthy circuit can supply power continuously during an emergency without outage. The utilization of such double-circuit transmission lines during normal and/or emergency operations is described. Maximum normal operating current based on fault duration, maximum allowable temperature of conductor, and thermal line ratings is evaluated. Several performances of dip/clearance affecting short-term emergency rating are also presented.