Korea Electric Power Corporation Power Research Articles

Design of 23kV 50MVA class HTS Cable in South Korea

The world first commercial project for the superconducting applications is already starting in South Korea. The first step of the project named SSS (Superconducting Smart platform Station in South Korea) is to operate AC 23kV 50MVA class HTS cable system in the power grid of Korea Electric Power Corporation (KEPCO) in order to increase the power capacity and realize the stable operation. The above HTS cable system will connect two substations between ShinGal and HeungDuk. Total length of the HTS cable is approximately over 1km including 2 sets of the normal joint box and 2 sets of the termination which are the out-door type accessories. Before performing the type test, various preliminary tests with the short cores were performed to confirm design of the HTS cable. To meet the design goals, the HTS layers of the core consist of the two conducting and one shield layer. The characteristics of the HTS wire is the non-magnetic 2nd generation wire. It can reduce the magnetization loss caused by itself and adjacent the HTS wires. The measured AC loss is around 0.3 W/m at 1,260 Arms and increasing trend of AC loss by operating current is the well fitted of simulation results. In case of short-circuit test, experimental temperature is approximately 77K and increased maximum temperature is under 92.8 K which is enough below the boiling temperature of LN2 at gage pressure 6.7bar.(g). A 70-meter-long the HTS cable including unit the test samples and an 85-meter-long LN2 return pipe will manufacture and installed for the type test at KEPCO Power Training Center in Gochang, South Korea. The type test procedure is following the Cigre TB538 and KEPCO standard those are including the 20 cycles load test, voltage tests such as AC withstand and impulse, repeated cooling process three times as prequalification quality test and visual inspection after disassembling. In the third quarter of 2018, LS Cable&System will supply and install AC 23kV HTS cable system in South Korea.

Cryogenic System for 80-kV DC HTS Cable in the KEPCO Power Grid

DC HTS cable has advantages in the absence of ac loss. Therefore, the Korea Electric Power Corporation (KEPCO) has started a project of operating and manufacturing technology for applying an 80-kV 500-MW 500-m-long dc HTS cable to the commercial power grid since 2011. LS Cable Ltd. has joined this project for designing and manufacturing an HTS power cable, and KEPCO has taken on cryogenic system and real power grid operation. The cryogenic system for an 80-kV dc HTS cable is composed mainly of Stirling-type cryocoolers. The Stirling cryocooler has been examined and verified by real grid operation in Icheon substation, and we therefore became assured of reliability for the cooling HTS cable system. We present the cryogenic system design, installation, and some results of preliminary tests in this paper.

A study on optimal SFCL specification to enhance the transfer capability on Korean power system

The Korea Electric Power Corporation (KEPCO) power system has the characteristics of the load being concentrated in the Seoul metropolitan region and direct power transfer from generations located at distant points in the system thereby resulting in high levels of fault current in the metropolitan region during fault conditions. This fault current problem in the metropolitan region has been a critical issue during the past few years where the increase in the load elevates the fault current levels thereby requiring the replacement of numerous circuit breakers. In order to reduce the fault current levels in the system, the installation of superconductivity fault current limiter (SFCL) has been considered as a solution to reduce the fault current levels in the system. In this paper, an optimal SFCL specification is proposed, by using the fault current contribution method, for siting the optimal location of the SFCL to minimize the current injection into the fault point. The effectiveness of the SFCL application is being verified by simulations based on the KEPCO power system planning data where several installation points are examined for effective reduction of the fault current issue in the system.

Profitability and productivity changes in the Korean electricity industry

The Korean electricity industry saw significant changes following the reform in April 2001. Until the last decade, the industry was monopolized by the Korea Electric Power Corporation (KEPCO), a state-owned, vertically integrated company. The 2001 reform divided KEPCO's power generation division into six power generation companies (GENCOs), with the aim of improving efficiency and introducing competition in the electricity industry. In this study, we used capital total factor productivity (KTFP) to analyze profit changes from fixed input capital, and an index number profit decomposition (INPD) to examine the sources of the profit changes. We investigate the industry thoroughly from three points of view: the overall industry over time; the power generation sector by company; and the transmission and distribution sectors of the Korea Electric Power Corporation (KEPCO). Next, we measured how the profits from productivity growth were distributed to consumers, fuel suppliers, employees, and company owners. The results suggest that a more reasonable price system for both wholesale and consumer prices needs to be implemented prior to the privatization and deregulation of the Korean electricity industry.

Performance Test of Cooling System for 500 m HTS Cable in KEPCO Power Grid

The high temperature superconducting (HTS) power cable has been successfully installed and operated for feasibility confirmation since 2006 at the power testing center of Korea Electric Power Corporation (KEPCO). The three phase 100 m long HTS cable with 22.9 kV/1.25 kA was manufactured and cooled by the open-loop of sub-cooled liquid nitrogen generated by a decompression cooling unit. No major fault has been observed during long-term operating test. As a next step, the design study of a 500 m long HTS cable system has initiated in 2008. Now, the HTS power cable was manufactured and installed at Icheon substation located near Seoul. In this paper, the cooling performance test of the 500 m long HTS cable in the real power grid is reported. Pre-cooling process using nitrogen gas is presented and the result of initial cool-down of the HTS cable is reported. Also, temperature as well as pressure drop in the system is discussed with respect to the loading current level.

Design and development of 500 m long HTS cable system in the KEPCO power grid, Korea

In Korea, two long-term field demonstrations for high temperature superconducting (HTS) cable have been carried out for several years; Korea Electric Power Corporation (KEPCO) and LS Cable Ltd. (LSC) independently. Encouraged at the result of the projects performed in parallel, a new project targeting the real grid operation was launched in the fourth quarter of 2008 with the Korean government’s financial support. KEPCO and LSC are jointly collaborating in the selection of substation, determination of cable specification, design of cryogenic system, and the scheme of protection coordination. A three phase 500m long HTS cable at a distribution level voltage of 22.9kV is to be built at 154/22.9kV Icheon substation located in near Seoul. A hybrid cryogenic system reflecting the contingency plan is being designed including cryocoolers. The HTS cable system will be installed in the second quarter of 2010, being commissioned by the fall of 2010. This paper describes the objectives of the project and design issues of the cable and cryogenic system in detail.

Empirical Modeling of Superconducting Fault Current Limiter Using Support Vector Regression

The superconductor-triggered type fault current limiter (STFCL), which was developed by Korea Electric Power Corporation (KEPCO) and LS Industrial Systems (LSIS), is under operation for the verification test at KEPCO's power testing center. The STFCL is composed of superconductor, fast switch and current limiting resistor. The fault current is suppressed after a half cycle by the method of a line commutation. In this paper, we investigated the empirical modeling of STFCL using principal components and auto-associative support vector regression (PCSVR) for the prediction and fault detection of the STFCL. Signals for the model are currents and voltages acquired from high-temperature superconductor (HTS), driving coil (DC) and current limiting resistor (CLR). After developing the empirical model we analyse the accuracy of the model. The results were compared with that of auto-associative neural networks (AANN). PCSVR showed much better performance in accuracy aspect. Moreover, this model can be used for the prognosis of STFCL system.

Damping Analysis using IEEEST PSS and PSS2A PSS

This paper scrutinized the damping effects of installing the prototype PSSs by a transient analysis for eight buses of faults in the South Korean power system. The PSSs used have the co-PSS blocks for IEEEST model with a single input and the co+power PSS blocks for PSS2A model with dual inputs. The simulation tool was a TSAT(Transient Security Assessment Tool) developed by Powertech Labs Inc. The voltages of the transmission line for simulations were 765kV and 345kV, and the faults for eight cases were sequenced by considering the open state and the close state of the lines. In the simulations, the three-phase line to ground (L-G) fault generated different points for each region. The simulations were compared to the cases of no PSS, partial IEEEST and PSS2A, absolute IEEEST, and absolute PSS2A to show that the power system oscillation can be effectively damped by PSS modules. Simulations were conducted to confirm the effectiveness for the KEPCO (Korea Electric Power Corporation) power system.