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An efficient method for analysis of the non-linear interaction between corona-generated space charge and the electric field is developed by minimizing an error function over the entire domain. The error function is defined in terms of current densities at each node by combining element errors that violate the divergence theorem. An iterative process can be effectively conducted without solving large system matrix. The electric field produced by the induced voltage is calculated by the method of moments (MoM), and the computational load is reduced by composing the system matrix exclusively on the conductor surface. To verify the performance of the proposed algorithm, the resulting current density and ground profiles of the electric field are compared to the results from the analytic method and the experiment.

The 765kV transmission line will be maintained by live-line works for efficient operation. In order to maintain the 765kV transmission lines safely by live-line works, lineman has to know switching impulse flashover characteristics of the jumper V-strings with damaged insulators in advance. In order to know the flashover characteristics this paper carried out experimental flashover mockup tests for jumper V-string with damaged insulators in the outdoors. And it suggests flashover characteristics of the 765kV jumper V-strings also. The results will be used in estimating the safety of live working for 765kV transmission lines.

To review application of HVDC (High Voltage Direct Current) transmission line to HVAC T/L in operation, reduced-scale model was designed and manufactured. The arms of model were designed to change height and interval of conductors. Electrical environmental interferences were estimated by various configuration of AC 345kV and DC 250kV T/L. The interferences such as electric field intensity and ion current density were measured and converted reduced-scale factor to full-scaled. Additionally, effects between AC and DC T/L were studied.

The influence of magnetic annealing on iron loss has been investigated in 0.1-mm-thick grain-oriented high-silicon steels. To prepare such thin high-silicon steels, 0.3-mm-thick commercial electrical steels were mechanically ground to a specific thickness and then annealed at 1200°C under a high vacuum atmosphere. Due to much faster evaporation of Fe than Si, strip thickness decreased and silicon content increased. The 0.23-mm-thick 3% Si samples typically were thinned to a thickness of 0.10 mm, and silicon content increased to 6.5% after annealing for approximately 50 h. The high-silicon steels were further magnetically annealed at 770°C in a dc magnetic field, and an excellent iron loss of around 0.65 W/kg (at 1.5 T/60 Hz) was obtained. The iron loss behavior with both siliconizing and magnetic annealing processes is discussed in the light of microstructural evolution of B2 ordering phases and domain boundary drag effect of surface subsidiary domains.

HVDC (High Voltage Direct Current) overhead transmission line was considered to prepare the interconnection between northeast Asian countries and inside power systems for the first time in Korea. For HVDC transmission lines, the corona discharge characteristics and space charge of conductors depend on the electric field conditions of the conductor, so transmission line designer have to estimate the electrical environmental effects such as radio, audible, and television noise from any set of conductors. In this paper, test method will be shown using reduced-scale test facilities of HVDC transmission line.

In this study, wrapping conductors with thin magnetic materials is proposed as a magnetic shielding method. The 0.1-mm-thick metal sheets of mu-metal, grain-oriented electrical steel, and nonoriented electrical steel were prepared from commercial alloy sheets through cold rolling and followed high temperature annealing. For magnetic fields generated by three-phase electric currents, mu-metal was the best in shielding performance when magnetic field at the shield point is about 90 ? T, yielding an excellent shielding factor lower than 0.1 in the vicinity of the shield. Above 490 ? T, however, silicon steels were better than mu-metal. Double-layer shielding with grain-oriented silicon steel (inner) and mu-metal (outer) resulted in an excellent shielding factor up to 490 ?T. These results are due to change in hierarchy of magnetic permeabilities of the materials with increasing magnetic field strength. For magnetic fields by single-phase electric current, on the other hand, a magnetic shield rather increased magnetic field or had no practical effect on shielding performance. This result is explained by superposition of original field vectors and secondary field vectors created by eddy currents within the materials.

Porcelain suspension insulators aged for 1, 5 and 10 years on Korean transmission lines and new insulators are tested for autoclave expansion. The compressive strength of the insulators aged in an autoclave with conditions of and at 20 atm for 30 minutes, was about , which is close to that measured on insulators aged for 10 years in the field. From simulation results, the cement displacement changed linearly with temperature. At a temperature of , the shear stress was approximately ; a stress that is brought about by a 0.07 % expansion of the cement. It is evident that the cement would fracture at a 0.07 % expansion, because the cement has about 7 to flexure strength. A turning point in the shear stress with mechanical load occurred at 0.02 % cement expansion. From an analysis of the porcelain body it is shown that there is sufficient margin of strength to guard against fracture of the porcelain body even for a cement expansion more than 0.12 %.

Various noises produced by corona discharges from high voltage transmission lines are the important considerations in line design. HVAC transmission lines must be designed to satisfy national environmental regulations too. Therefore, it is necessary for line designers to pre-evaluate environmental problems using prediction tools. In this paper, an environmental design software, TLCALC 2001 for AC transmission lines as a comprehensive window program is introduced. It has 6 modules including audible noise, radio noise, television noise, magnetic field, electric field and conductor surface gradient module. TLCALC 2001 has solved some of the problems of the existing foreign tools and has several advantages over those. 1) It is a common tool that has solved calculating limitations of foreign formulas. 2) It has a wide application range and enhanced prediction accuracy. 3) It can be applied to almost all transmission line configurations in Korea. 4) Experienced designers can get calculation results within about 15 minutes. As the use of TLCALC 2001 is easy and practical, it will be applied to the environmentally friendly design and construction of transmission lines. It is expected that public complaints and social environmental costs will be considerably reduced by the use of TLCALC 2001 in the future.

This paper presents the results of long-term electromagnetic interference (EMI) measurements on the bundle of 6 Cardinal conductors tested at Korea's Kochang 765-kV full-scale test line. The instrumentation and the most important features of the facilities are also described. This new 3-phase double circuit test line can be energized at line-to-line voltages up to 850 kV. The analysis of the data shows that the 6-Cardinal conductor bundle meets the radio and television interference guidelines of the Korea Electric Power Corporation (KEPCO).

To satisfy an annual rate load growth of approximately 10% per year, Korea Electric Power Corporation (KEPCO) has been studying the use of double circuit 765-kV transmission lines. Since this would be the first application in the world for such lines, a 765-kV test line was built near the Yellow Sea to gain experience with this higher voltage. A primary corona phenomena that is important for conductor selection is audible noise (AN) due to corona. This paper presents the results of long-term measurements of AN from the 765-kV double circuit test line using a bundle of 6-483.8 mm/sup 2/ conductors at Korea Electric Power Research Institute's (KEPRI) 765-kV test station. The analysis of the data shows that the 6-rail conductor bundle satisfies the AN criterion of 50 dB(A) under rainy weather conditions.

A HVDC test line that functions as a prototype variation was constructed in Korea, after considering the main functions and characteristics of diverse ±500kV DC transmission test line towers and the results of the analysis of the line's insulation, environment, fitting, transmission equipment, economic feasibility, and operational efficiency. The variable prototype test line has advantages in line-related researches, including in the fitting design, insulation coordination design, line construction technology and transmission equipment development, and does not require high-cost towers, unlike overseas test lines. The maximum applied voltage of the newly constructed DC test line was ±600 kV, and a measurement system was established around the line to evaluate the interference factors. Tests on various environmental characteristics will be performed to derive the optimal pole arrangement coordinates for the Korean environment, while changing the pole arrangement and height of the line using a large hoist installed at special arms in tower No. 2 and 3.

Corona discharges form at the surface of a transmission line conductor when the electric-field intensity on the conductor surface exceeds the breakdown strength of air. In order to decrease the electric-field intensity on the conductor surface, a new 6 conductor bundle has been studied. This bundle, asymmetrical-sized conductor bundle, consists of a large subconductor at the bottom two conductor positions in the 6-conductor bundle of each phase of the line. The electric field intensity on these two large subconductors is reduced which in turn reduces the corona noise. It is proven that the newly proposed method is a better solution for decreasing the electric- field intensity than either the conventional bundle or the asymmetric bundle proposed by EPRI(Electric Power Research Institute).

In this work, prior measurements have been carried out of the human exposure to magnetic field near power facilities in Korea according to the measurement procedures of IEC PT62110. These measurements aim for evaluating the exposure levels by use of newly proposed IEC PT62110 of the human body to the magnetic fields on general public. For this purpose, statistical treatment has been conducted with the measured data for the uniform and non-uniform magnetic field exposure.

In Korea, as a way to expand electric capacity in power line with increasing of electric power demand, the STACIR/AW (super thermal-resistant Al alloy conductors Al-clad Invar-reinforced) conductor are used. The STACIR/AW consists of stranded INVAR/AW wire as core material for sag control and heat-resistant Al alloy for ampacity gain which was developed to catch up with tremendous increase of electric power demand. These two different materials enable the STACIR/AW to operate at a higher temperature compared to a conventional ACSR (Al alloy Conductors Steel Reinforced) without modifications to the tower. It is generally accepted that the continuous operating temperature of STACIR/AW is 210degC which is remarkably high compared to that of ACSR, 9degC. But some case of 480 mm2 STACIR/AW (conductor named Rail) of the commercial line, there are some problems with regard to sag characteristics. This paper describes the results from a long term maximum permissible current characteristic experiment using full scale test line which is energized up to 3000 A. Also the variation of fatigue property with heat exposure in stranded conditions will be presented.

This paper describes corona and electric field effects studies of a 765 kV double circuit test line. In Korea there are many mountains and it is very difficult to get the right of way because the population density is very high and the territory is small. So Korea Electric Power Corporation (KEPCO) decided to build one double-circuit 765 kV line of vertical arrangement configuration instead of two single-circuit 765 kV lines of horizontal configuration. Corona performance on several candidate conductor bundles has been investigated with a corona cage since 1984 by KEPRI. We have known that a bundle of 6-Rail (29.61 mm) conductors per phase is the optimum and its audible noise (AN) level L/sub 60/ in the corona cage was measured as 45.0 dB(A) in GE method. To investigate the electrical environmental impact of the future commercial line with this conductor bundle, KEPRI built a full scale 765 kV test line in 1993 as the second step study. Long-term measurements have been made in this double-circuit test line. We have found that the AN data were very close to that predicted by BPA Corona and Field Effects computer program, however, the RI data in fair weather was higher than the predicted by the BPA program by 2.4 dB (/spl mu/V/m). AN L/sub 60/ in foul weather is below 50 dB(A). We think the 6-Rail conductor bundle is the optimum size in the 765 kV double-circuit transmission line from the environmental view-point.

The present paper reports the analysis results by comparison of characteristics of electrical environment between different EHV transmission lines such as AN (Audible Noise). RI (Radio Interference), TVI (Television Interference), EMF (Electric and Magnetic Field). In Korea, transmission lines with nominal voltage of 765-kV have been constructing since 1996, and Hungary energized a 750-kV line in 1978. However both EHV transmission lines have different line configuration, Korea is a prime example of the first double circuit 765-kV line in the world, and Hungary has been operating one ofthe single circuit 750-kV.