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This paper introduces the insulation coordination study results for UHV AC systems which was performed by CIGRE working group. The study results will be discussed within IEC technical committee in order to amend the IEC Insulation Coordination 60071-1 Ed. 8 2010 and 60071-2 Ed. 3, 1996. This paper includes the insulation coordination of transformer, gas insulated switchgear, metal oxide arresters and clearances of transmission towers. This article also illustrates the overvoltage specific to UHV systems such as TOV(temporary overvoltage), switching overvoltage, lightning overvoltage and VFTO(very fast transient overvoltage).

Substation Automation System is basically operating throughout communicative services among IEC 61850 based devices. So, minimum requirement in order to install the system in the substation is to verify server and client conformance. This study aims to develop IEC 61850 SA client conformance testing system for verifying the full communication conformance of the substation automation system and this paper describes the design and implementation of the testing system.

The outages of transmission lines give big damages to the industrial world Lightning outages occupy above 50[%] among the outages of transmission lines. To decrease the lightning outage rates, it is necessary to try countermeasures considering economical points. For the lightning protection of power transmission lines, it is very important to accurately predict the lightning outage rate because the reliability criterion for transmission line is normally specified as the number of flashovers per 100[km] per year. The phenomenon of an insulator flashover by a lightning stroke is a very complex electromagnetic event. And to calculate the lightning outage rates of transmission lines, so many calculation should be repeated because there are many overhead lines and power lines. Therefore it is necessary to develope a program for it. In this paper, we briefly introduce the basic concept for lightning outage calculation algorithm and the program.

This paper analyzes arc phenomena including the secondary arc's elongation in the Korean 765kV single transmission line (79km) between Sin-Ansung S/S and Sin-Gapyeong S/S, which will be installed in Korea in June 2006. In particular, both frequency independent and frequency dependent line models are compared to make our final decisions. As well, the significant simulation results are investigated by the EMTP program. As a result, there is no need of HSGS in the Korean 765kV single transmission line from both a practical and an economical point of view.

This paper presents the results of the air clearance design on the KEPCO 765 kV double circuit transmission system. At first the authors performed the switching overvoltage study. The switching overvoltage was analyzed by EMTP (Electro-Magnetic Transient Program) and TNA (Transient Network Analyzer). The full scale test for the air insulation strength of 765 kV double circuit transmission towers was performed by a 4 MV outdoor impulse generator. The simultaneous fault clearing case of a single line-to-ground fault at each circuit was considered because the probability of simultaneous single line-to-ground fault at each circuit is very high. However, the reclosing overvoltages with preinsertion resistor are lower than the simultaneous fault clearing overvoltages when the transmission line is short (about 170-180 km). The maximum phase to ground switching overvoltage in the simultaneous fault clearing case is 1.9 p.u. and the maximum switching overvoltage between phase to phase is 3.3 p.u. The required air clearance in a tower at the altitude of below 1000 m is 4950 mm to endure the maximum switching overvoltage of 1.9 p.u. The standard deviation of 5% in switching surge flashover voltage was verified from the full scale test.

IT technology development led to introduce automation systems in the substation. But, it was difficult for IEDs to communicate each other because there were different protocols over 152 kinds. Therefore, IEC 61850 for the substation was standardized. It can be applied to dispersed power-based micro grid or smart grid. In this paper, we inform the case that we implemented a client conformance tool to communicate with IEC 61850-based IEDs. And the client conformance tool was certified by KEMA, international certification association.

To develop large-scale electricity industry continuously, Power systems are requested to be high confidence. And digital & automation-based technology is needed over the length and breadth of power system management. As a result of this, IEC 61850, which is standard for building automation systems, was established for dispersed power. All systems and devices are also required to change into digital and network-based systems. In this paper, we propose the outline how digital substation automation systems develop, and share application cases.

A. Ametani comments on the paper by J.H Kim et al. (see ibid., vol.15, no.1, p.381-6, 2000). The author briefly describes his own work on overvoltage evaluation using EMTP on a 1100 kV transmission line of Tokyo Electric Power Company and asks the original authors to comment on his work and on the effect of frequency on EMTP and TNA simulation results. The original authors reply to the comments.

The paper deals with the cost evaluation concerning the implementation of a 2000MW HVDC link over a 200km distance. Two different dc voltages have been considered, namely +/−300kVdc and 500kVdc. Two different scheme configurations have been considered, namely a single bipole system and a double bipole system.