Byeongmo Yang

Installation and Testing of SFCLs

A 22.9 kV/630 A-class superconducting fault current limiter (SFCL) was installed on a distribution line in Icheon Substation for real-grid operation. The substation is located in a semi-urban area with moderate loads. The SFCL is of hybrid type. After installation it was subjected to a series of on-site tests. Test procedures were determined by following convention in testing both superconductivity-related and not-related specifications of the SFCL. Tests performed were minimum limiting current test, temperature test, dielectric test, and impedance measurement. After successfully passing the tests, the cooling system of the SFCL was operated for more than 5 months under various load conditions to optimize the operation condition. During that period, temperatures, liquid nitrogen level, and internal pressure remained within ±0.1 K, ±0.5 cm, and ±0.5 bar range, proving stability in cooling superconducting elements. The SFCL was then energized and went into real-load operation successfully.

Qualification Test of a 80 kV 500 MW HTS DC Cable for Applying Into Real Grid

Until now, some countries including South Korea have made considerable progress in the development of HTS (High Tc Superconducting) power equipment. Superconducting power cable systems are the strongest candidate from the viewpoint of their use in the real grid owing to their high current capacity. Specially, in the future, high-current long-distance HTS DC cables will play an important role in power transmission systems because, in contrast to HTS AC cables, HTS DC cables experience nearly no loss. In this paper, the authors suggest a new testing method for the load cycle and suitable thermal cycles to meet the requirements for HTS DC cables to be applied to the real grid. A prototype 100 m/3.25 kA/80 kV HTS DC cable system was developed for the qualification test in South Korea. The qualification test was carried out, based on HTS experience, the international standard for HTS AC cables, and the standards for conventional HVDC cables. It was performed in the same manner as that for a conventional HVDC cable for 6 months in the KEPCO PT (Power Testing) Center. Since its successful qualification test, the 500 MW/80 kV HTS HVDC cable system will have been operated in the KEPCO real grid since 2015, to evaluate its practical requirements and confirm its technical feasibility. This paper presents the recommendations and results of the qualification test for HTS DC cables.

Loss Characteristic Analysis of an HTS DC Model Cable Connected to a Model VSC-HVDC System

The purpose of high-temperature superconducting (HTS) cables as the transmission conductor in a high-voltage dc transmission system is mainly to reduce the Joule losses arising from the power transmission process. However, the harmonic currents generated from the switching behavior of the voltage source converters result in power loss in the HTS dc power cable. The cable loss characteristic should be analyzed in terms of its practical applications. In this paper, the harmonic currents characteristics were analyzed in both steady and transient state. An HTS dc cable model was also developed using the finite elements method to examine its loss characteristics. The results showed that the harmonic loss of the HTS dc model cable depends on the properties of the voltage source converters, the operating dc current level, and the ac system conditions. This work will be useful in studying the loss analysis of a real HTS dc power cable.

Loss Characteristic Analysis of HTS DC Power Cable Using LCC Based DC Transmission System

The zero resistance of superconducting material is observed only with a DC current, while transmission loss occurs with an AC current. Power converters use electronic devices which generate harmonic currents due to their high switching frequency. The authors expect that harmonic currents also influence the losses in the superconducting DC power cables of a DC transmission system. The authors have developed a miniaturized superconducting DC transmission system with 12 thyristors based AC/DC converter and a 2 m length superconducting cable connected to the DC side between two converters. The capacity of the converter is 20 kW and the critical current of the HTS DC power cable is 140 A. In this paper, the HTS DC power cable loss characteristics were anal- ysed by the fabricated home-made thyristor converter system.

Specifications of the 22.9 kV SFCL Considering Protection Systems in Korean Power Distribution System

The GENI project for applying the 22.9 kV HTS cable and the SFCL to real power system has been progressed in South Korea since 2008. The HTS power devices were applied to the Icheon substation in the real Korean power grid in August 2011. This is the first demonstration of HTS power devices in South Korea. For a successful application, this paper proposes proper specifications of a current limiting resistor/reactor and an activating current for the 22.9 kV SFCL in the Korean power distribution system. These specifications are determined, considering the protection system of real Korean power system.

Protective Relay Tests of Hybrid SFCLs in a Korean Distribution Power System Using RTDS

A study on protective relay systems is one of the important technical issues concerning power systems that use Superconducting Fault Current Limiters (SFCL). We used a Real Time Digital Simulator (RTDS) in order to study the true interaction of the protection system with the power systems. RTDS modeling of SFCL is necessary to obtain detailed protective relay tests. In this paper, we developed an analysis model using RTDS in order to study the transient behavior of a 22.9 kV hybrid SFCL and performed closed-loop testing on a protective relay in a distribution power system using the developed SFCL model. The model uses an operation mechanism of the real SFCL. The 22.9 kV hybrid SFCL is under development by LSIS (LS Industrial Systems Co., Ltd.) and KEPRI (Korea Electric Power Research Institute) in Korea. The parameters of the model are based on the test data from the real SFCL. Power system planners and operators will be able to solve the problems that are expected in the application of SFCLs to power systems by using these protective relay testing results.

A Novel Multi-Terminal Based Evaluation Method for an HTS DC Power Cable

High current capacity is one of the advantages of a superconducting power cable system. However, it creates difficulties when experimenting to analyze its characteristics. Short-length superconducting cables for a laboratory-scale experiment system present problems: large operating current and current distribution by terminal resistance. Experimental conditions, such as transient states, are limited by power supply capacity. In this paper, the authors suggest a new experimental method for the high-temperature superconducting (HTS) power cable to reduce the capacity of a power supply and solve current distribution problems. For the suggested method of this paper, each HTS wire has separated terminal and each HTS wire was connected in series through the separated terminal. All of HTS wires in the HTS power cable are insulated and connected in series. The cross-sectional area of the HTS power cable is the same, but the terminal structure is different. Thus, all HTS wires have the same current and cross-sectional area of HTS power cable. It is possible to test a large capacity HTS power cable under the transient state or fault conditions using a small-size power source. The design concept, configuration of the experiment system, and the experimental results were discussed in detail in this paper.

Optimal Design Specifications of 22.9 kV HTS-FCL Applied in Real Korean Power System

KEPCO decided to apply the HTS FCL and cable in real substation in 2009. This is the first commercial demonstration case and starting point of the HTS equipment in South Korea, even though this is not a general perfect commercialization. For a successful application on this commercialization preliminary, it is quite important to design the HTS-FCL specification with regard to the current status of the application site (for example, the existence of NGR (Neutral Grounding Reactor), 3-winding low% impedance and so on). This paper evaluates the necessary and sufficient design specifications of the 22.9 kV HTS-FCL to fulfill the real power system conditions. It investigates the detailed design criteria, short circuit capacity, FCL impedance, protection scheme, fault limiting type and other design parameters to learn the real status of ICHEON substation which will be using the HTS- FCL.

Expected Future Market Volume of HTS Equipment in South Korea

This paper shows the entire future market volume of the HTS power industry, one of main smart grid equipment, in the case of the final market penetration ratio reaching 100% in the domestic market (South Korea). In this paper, the market penetration ratio is determined using the judgment method, with the market penetration S-curve induced using the Delphi method and the Product Life Cycle from 2011 (supposed launching year, not realistic physical year), to 2050 (expected final target year). This paper analyzes the HTS market penetration ratio of each stage, apparent innovation, early adapters, and the early/late majority and laggard stage, using the S-curve, thus calculating the total future market volume of HTS equipment in the positive sense. Finally, this paper estimates the quantitative analysis results for the HTS4-items (cable, FCL, transformer, rotation machine) of each year within the domestic market.

Short Circuit Withstanding Capability of 22.9kV HTS Cable in Korea

AbstractIn Korea, GENI(Green superconducting Electric power Network at the Icheon substation) project has been conducted since 2008. The objective of the GENI project is to install and operate a 22.9kV/50MVA High Temperature Superconducting (HTS) cable system and a 22.9kV/630A Superconducting Fault Current Limiter (SFCL) system in the Icheon substation located near Seoul. It is important to design specifications considering real power system conditions for a successful application of the HTS cable and SFCL system to a real grid. This paper proposes a design specification for the short circuit withstanding capability of the HTS cable to apply to Korean power distribution system, from the viewpoint of a protection system. The HTS cable system with the proposed specification has been operated in the Korean real grid of the Icheon substation since August, 2011.