• Journal of IKEEE
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• v.18 no.4
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• pp.442-446
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• 2014

A method for applying emergency ratings to improve the reliability of power supply in ACSR overhead transmission lines is described in this paper. Due to re-regulate power industry, most power companies worldwide as well KEPCO have been searching for only economical strategies without new investment. Power demand was rapidly increasing, however, generation amount did not follow sufficiently. Hence in order to increase the transmission capacity for the existing transmission lines in case of peak load, or contingency in transmission lines, an application method of emergency ratings such as short or long term rating is proposed. If applying long term emergency rating instead of static line rating for the period of a peak load, power transmission can be increased to 10 % or more. Furthermore, it was shown that emergency rating can be effectively used in the contingency of double-circuit transmission lines and/or overload cases.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.7
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• pp.20-28
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• 2007

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.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.8
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• pp.432-437
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• 2004

Since the characteristic frequency is decreased in proportion to the fault distance, the characteristic frequency component may be insufficiently eliminated by a low-pass filter on a long transmission line. In order to set a standard for the cut-off frequency of the low-pass filter, this paper proposes a method for obtaining the characteristic frequencies due to line faults. The application results of the proposed method are presented for line to ground (LG) faults and line to line (LL) faults on a 345 kV 200 km overhead transmission line. The EMTP is used to generate fault signals under different fault locations and fault inception angles. By comparison between the characteristic frequencies obtained from the proposed method and the EMTP simulation, it is shown that the proposed method accurately obtains the characteristic frequency.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.323_324
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• 2009

345kV Incheon Thermal Power Plant Transmission Line Collapse Analysis and Countermeasures. The Typhoon Galmaegi which had been formed in July 15, 2008 diminished into a tropical cyclone and cooled the air above the West Sea. The cooled air colliding with the warm inland air caused a strong whirlwind at some places in the west seaside; the whirlwind battered the 345kV Incheon Thermal Power Plant Transmission Line to be collapsed. The resistance against wind pressure, one of the key elements in transmission line engineering, is designed to endure the pressure corresponding to the maximum instantaneous wind speed. Before the above accident happened, no transmission line has ever been collapsed by a whirlwind. So this paper is aimed to analyze causes that collapsed 345kV Incheon Thermal Power Plant transmission line and to introduce countermeasures.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.335-336
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• 2008

Overhead transmission lines are mainly crossing mountainous area. They are easily affected in weathers like typhoon, strong wind, lightning, heavy rain, or heavy snow. Sometimes these weathers cause transmission line faults. A lightning flashover is most often fault. Nowadays lightning density in KOREA is growing high and lightning flashovers occur more often. A lightning flashover on transmission line is mostly cleared by momentary operation of a circuit breaker, so power failure happens rarely. However, when both circuits trip simultaneously due to the lightning flashovers on double circuit transmission line, short time power failure and voltage drop happen. KEPCO has used transmission line arresters to avoid double circuit simultaneous trip out since 2003. And transmission line arresters cannot be installed with KEPCO's present metal fittings, so various fittings have been used for each transmission line arrester manufacturer. This paper introduces development and standardization of arc-horn and metal fittings for transmission line arrester which can be used for both existing lines and new lines in KEPCO.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.10
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• pp.593-601
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• 2003

Distance realy is tripped by the line impedance calculated at the relay point. Accordingly the accurate operation depends on the precise calculation of line impedance. Impedance can be accurately calculated in case of overhead line. However, in case of power cables or combined transmission lines, impedance can not be accurately calculated because cable systems have the sheath, grounding resistance, and sheath voltage limiters(SVLs). There are also several grounding systems in cable systems. Therefore, if there is a fault in cable systems, these terms will severely be caused much error to calculation of impedance. Accordingly the proper compensation should be developed for the correct operation of the distance relay. This paper presents the distance calculating algorithm in combined transmission line with power cable using wavelet transform. In order to achieve such purpose, judgement method to discriminate the fault section in both sections was proposed using D1 coefficient summation in db4. And also, error compensation value was proposed for correct calculation of impedance in power cables section.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.519-521
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• 2003

This paper presents a frequency analysis of subspan oscillation on overhead transmission line. The Oscillation frequency is a natural characteristic of a subspan and can be calculated. But it is not same to calculated frequency, because it has been composed several frequencies of adjacent subspan. We were analyzed to the frequency of subspan oscillation by FFT methods. This result will use to establish of the subspan location rules.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.522-524
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• 2003

This paper presents a stability estimation method for subspan oscillation on overhead transmission line. It has been used method by conductor's fatigue limit or subspan oscillation amplitude. But it is not proper to estimation of subspan oscillation. We suggest to instability index for estimation method of subspan oscillation. And we tried to 4 bundled conductor system. This result will use to establish of the subspan location rules.

• Wind and Structures
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• v.3 no.4
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• pp.243-253
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• 2000

To develop galloping suppression devices, it is important to understand the effects of wind turbulence on galloping and to establish an evaluation method which takes 'large conductor deformations' into account. This paper introduces some findings on galloping in gusty wind obtained by numerical simulation using a model based on the Mogami Test Line of the Tokyo Electric Power Co. The equations of motion of the conductor are based on the Lagrangian formulations by Simpson, and they are made discrete in accordance with a finite element method.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.5
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• pp.245-249
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• 2006

Corona characteristics of conductors are dependent on the electric field conditions in the immediate vicinity of the conductors. In case of DC transmission line, particularly, the space charge plays an important role in the electric field distribution. Therefore, DC corona cage simulation is necessary for long-term test in the same conditions. This paper presents the results of designing and constructing hardwares such as DC power supply, measurement system and DAS to carry out the simulation. The corona cage longitudinally is divided into five equal length sections and three inner sections of those are isolated from the ground of outer cage. The measurement items are radio noise, corona current, television noise, audible noise and meteorological conditions. In the next step, various simulations about the type and configuration of two or three candidate conductors will be conducted. And then finally an environmentally-friendly conductor for HVDC overhead transmission line will be decided.