High Temperature Superconducting Cable System Research Articles

Reliability Analysis of HTS Cable Systems

In this study, a reliability model of a high-temperature superconducting (HTS) cable system is proposed. There are two versions of this HTS-system reliability model, depending on the scope of its application. As an independent system, there are three operating states in an HTS system, that is, a normal state, a postponable outage state, and an outage state. The probability and frequency of each state are calculated using the Markov model. However, when used as part of a distribution system, a derated state is added to the model because of the unique overcurrent behavior of the HTS cable system. The probability of this derated state depends on the condition of the HTS cable system. The proposed models are applied to an HTS cable project planned by the State Grid of China. The results illustrate the effectiveness of a backup refrigerator in the cooling system. The effects of a spare line in parallel with an HTS cable are quantitatively estimated with the model. The reliability of an HTS cable can be calculated using the proposed models if the required data are available.

Results of Japan's First In-Grid Operation of 200-MVA Superconducting Cable System

A high-temperature superconducting (HTS) power cable demonstration project was started in 2007 to evaluate the cable's performance, stability, and reliability. This project aims to operate a 66-kV 200-MVA HTS cable system in a real power grid of the Tokyo Electric Power Company. A 240-m-long HTS cable was successfully installed, and other system components, such as a cable-to-cable joint, terminations, and a cooling system, were also constructed at the Asahi Substation in Yokohama. After several completion and performance tests on the system, the HTS cable was connected to a real grid from October 29, 2012 to December 25, 2013. The in-grid operation had continued for more than one year without any accidental interruption of the operation or troubles of this system. The temperatures and pressures of liquid nitrogen flowing in the HTS cable were controlled to within the target values. After the in-grid operation, the critical current of the HTS cable was measured, and it was confirmed that there was no degradation compared with the initial results. In addition, no partial discharge was observed in periodical measurements. It is concluded that the HTS cable system has good performance and stability for long-term in-grid operation.

Thermal Modeling of Gaseous Helium as a Cryogen for High Temperature Superconducting Cable Components

A fluid mechanics and cryogenic thermal study of the termination system of a gaseous helium cooled second generation high temperature superconducting (HTS) cable is presented. This includes a discussion on the development of a 2-D turbulent model that uses finite element method within COMSOL to assess the temperature profiles in the terminations and the comparison of the model results with those obtained experimentally. Temperature gradients across the cable system were measured before an actual HTS cable was installed to ensure that they are within an acceptable range and to validate the cryogenic design of the cable terminations. The experiments were conducted at the gaseous helium cooled superconducting cable test facility at the Center for Advanced Power Systems (CAPS), Florida State University. The thermal model presented here confirms that temperature gradients across a 30-m-long HTS cable system operating at around 50 K can be maintained below 6 K with helium gas mass flow rates of <;10 g/s. The results of the thermal models agree with the experimental results. The modeling methods used and the resulting thermal model reported will be useful for future design studies in optimizing the cryogenic thermal and fluid flow designs of superconducting cables.

Experimental Results of 275-kV 3-kA REBCO HTS Power Cable

A 30-m-long 275-kV 3-kA high-temperature superconducting (HTS) cable had been developed in a national project of the Materials and Power Applications of Coated Conductors project in Japan. The design of the cable was based on the design values obtained from ac loss properties, thermal behavior under short-circuit tests, and electrical properties, such as partial discharge properties, impulse withstand properties, and dielectric properties. Through the development, the material of the cable insulation was determined and designed on the basis of its design stresses and test conditions based on the IEC, JEC (Japan electrical standards), and other HTS demonstrations. This cable was also designed to withstand a short-circuit test of 63 kA for 0.6 s and to have low losses of 0.8 W/m at 3 kA, 275 kV, including ac loss and dielectric loss. Based on these designs, a 50-m cable was manufactured and tested. The short samples obtained from 50 m were confirmed to have the designed characteristics. Furukawa Electric constructed a demonstration system of a 30-m cable with two terminations and a cable joint. The demonstration had started since November 2012 at Shenyang in China. In this demonstration, a 30-day long-term test was conducted and monitored at a current of 3 kA and at a test voltage selected to verify a 30-year operational lifetime. Removal tests revealed the superior reliability of the 275-kV HTS cable system.

Design of 110kV/2kA High Temperature Superconducting Cable Termination Stress Cones

High temperature superconducting (HTS) cable termination is an important component of the HTS cable system, which functions to connect the HTS cable and the conventional cable accessory. The stress cones of the HTS cable termination can improve the internal electric field distribution and the electrical insulation strength of the cable termination. In this paper, the mathematical model and equivalent circuit model of the stress cones are built and the genetic algorithm is adopted to the design of 110-kV HTS cable terminal stress cone. The capacitance, radial electric field, axial electric field, voltage, insulation thickness and other parameters of the stress cone were compared before and after the optimization of the stress cone. Finally, the simulations of the stress cone with the optimized structure were made using finite-element analysis software COMSOL to test the optimization result.

Characterization of Partial Discharge With Polyimide Film in $\hbox{LN}_{2}$ Considering High Temperature Superconducting Cable Insulation

High temperature superconducting (HTS) cable has now reached the stage where their application in power systems is in the process of being implemented. Liquid Nitrogen (LN 2 ) and polyimide film have been used as a coolant and insulation in HTS cable systems. Partial discharge (PD) events may lead to material degradation and total breakdown. PD testing is an important quality check for the insulation of HTS cable. Thus it is necessary to consider PD for the insulation testing in LN 2 which is generated in void defects of the insulation layers. The PD characterizations of polyimide film in different defects were investigated under 50 Hz AC voltages in LN 2 and at room temperature (298 K). The results show that the number of discharges and the discharge quantity increase with the increasing of the applied voltage and the defect size. The PD inception voltage decreases when the void defect diameter enlarged and it is higher in LN 2 than that at room temperature. The maximum field strength for HTS tape insulation increases with the defect close to the tape boundary and the addition of contaminant relative permittivity. Obtained results at cryogenic temperature provide necessary information for insulation design and pre-shipment inspections of HTS cable system.

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.

Japan's First In-grid Demonstration of a High-&lt;i&gt;T&lt;/i&gt;&lt;sub&gt;c&lt;/sub&gt; Superconducting Cable System

High-temperature superconducting (HTS) power cable has significant merits of compactness and large power transmission capacity. To evaluate its performance, safety and reliability, HTS cable system was constructed at Tokyo Electric Power Company's Asahi substation in Yokohama, and the HTS cable had been connected to a real grid from October 29, 2012 to December 25, 2013 for the first time in Japan. The in-grid operation had continued for more than one year without any accidental interruption of the operation or troubles of the system. It is concluded that the HTS cable system has good performance and stability for long term in-grid operation. This paper describes the result of the HTS cable demonstration and their characteristics.

Numerical Analysis of Heat Transfer and Fluid Characteristics of Flowing Liquid Nitrogen in HTS Cable

High-temperature superconducting (HTS) cable has heat intrusion from the termination including joule heat generation at the terminal joint and from the room temperature cable through the Cu current lead. According to the length of the HTS cable, this heat loss may become a considerable amount which cannot be ignored in the HTS cable system. In this study, referring to a high-voltage cable (HV cable) which was developed in M-PACC project, the effect of heat transfer at the interface between the terminal joint and LN2 in the terminal vessel (ho) on the temperature of the HTS cable were calculated and evaluated. The condition of flow in the terminal vessel was assumed to be natural convection, forced flow or static condition for evaluating this effect with various heat transfer condition. As a result, in the case of the natural convection, most of heats flow into the LN2 in the terminal vessel where the volumetric flow of the LN2 is large since ho becomes high. Accordingly, the temperature rise of the LN2 in the inner pipe of Cu former and the terminal vessel can be restricted. However, in the cases of the forced flow and the static condition, most of heats flow into the LN2 in the inner pipe where the volumetric flow of the LN2 is small since ho becomes small. Accordingly, the temperature rise of the LN2 in the inner pipe becomes high. This temperature rise of the LN2 in the inner pipe makes the temperature of the HTS conductor large resulting in remarkable increase of AC losses. Consequently, on the HV cable design, for restriction of the AC loss increase, it is expected that designing the HTS cable termination such as extending outer surface of the terminal joint for increasing of the heat inflow from the terminal joint to the LN2 in the vessel is effective.

Design and Analysis of HTS Cable Termination Stress Cones

High-temperature superconducting (HTS) cable terminal is an important part of the HTS cable system, which functions to improve the internal electric field distribution and the electrical insulation strength of the cable termination. In this paper, the particle swarm optimization method is adopted to the 35-kV HTS cable terminal stress cone. The capacitance, radial electric field, axial electric field, voltage, and other parameters of the stress cone were compared before and after the optimization of the stress cone. The simulations of the stress cone with the optimized structure were made using finite-element analysis software ANSYS. Finally, a capacitor voltage test verifies the equal capacitance and gradient design of stress cone.

Update of YOKOHAMA HTS Cable Project

The high-temperature superconducting (HTS) cable demonstration project supported by Ministry of Economy, Trade and Industry and New Energy and Industrial Technology Development Organization has started in Japan. The target of this project is to operate a 66 kV, 200 MVA HTS cable in the live network of Tokyo Electric Power Company in order to demonstrate its reliability and stable operation. The design of the HTS cable with DI-BSCCO has been completed as well as those of a termination and a joint. A 30-m HTS cable system with terminations, a splice, and a cooling system was installed in the SEI facility and confirmed the cable has good performances as design. The HTS cable, splice box, and termination vessels have been manufactured with the same design of a 30-m cable system. By now, the HTS cables have been installed into the conduit at the Asahi substation of Tokyo Electric Power Company. The constructions of splice and terminations have been completed. The HTS cable system at Asahi substation was cooled down in this spring. This paper describes the design and completion test results of the HTS cable system.

In-grid Demonstration of High-temperature Superconducting Cable

Abstract The first in-grid demonstration of a high-temperature superconducting (HTS) cable system in Japan was carried out to verify its reliability and stable operation. The cable design was completed in association with DI-BSCCO and a pre-performance test of a 30- m HTS cable system was carried out to check its operation. A HTS cable was manufactured for demonstration purposes and passed all shipping tests. The installation of the cable was successful, and system construction has now been completed. After confirmation of the soundness of the cable system, it was connected to a live grid and the in-grid demonstration commenced in October 2012.

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.

The insulation coordination and surge arrester design for HTS cable system in Icheon substation

This paper proposes an insulation coordination and surge arrester design for HTS (High-Temperature Superconducting) cable system in Icheon substation in Korea. In the aspect of the economic analysis, since the HTS cable is very expensive, the insulation coordination to prevent the dielectric breakdown caused by the lightning surge should be considered carefully. Also, in the aspect of the power system reliability, since the HTS cable has much more capacity compared than conventional power cables and the ripple effect from the HTS cable failure may lead to the wide area blackout, an intensive study for insulation coordination from lightning surge is one of the most important considerations. In this paper, the insulation coordination for lightning surge is verified using HTS cable and power equipment models and the design of the proper surge arrester is proposed.

고온초전도 DC 케이블 시스템용 PPLP 및 GFRP의 절연 특성

DC high-temperature superconducting(HTS) cable system has attracted a great deal of interest from the view point of low loss, dense structure and large capacity. A HTS cable system is made of cable and termination. The insulating materials and insulation technology must be solved for the long life, reliability and compact of cable system. In this paper, we will report on the dielectric breakdown characteristics of insulating materials for HTS cable and termination. The AC, DC and lightning impulse breakdown strength of laminated polypropylene paper(PPLP) and glass fiber reinforced plastic(GFRP) have been measured under nitrogen pressures in the range of 0.l-0.4MPa. PPLP and GFRP are found to have a significantly higher DC breakdown strength. Also, DC surface flashover voltage of negative polarity is slightly higher than that of positive polarity in GFRP.

Status of Superconducting Cable Demonstration Project in Japan

The HTS cable demonstration project, called the Yokohama Project, supported by Ministry of Economy, Trade and Industry and the New Energy and Industrial Technology Development Organization, was initiated in Japan in 2007. The aim of this project is to operate a 66 kV, 200 MVA high-temperature superconducting (HTS) cable in a network of the Tokyo Electric Power Company to demonstrate cable reliability and stable operation. Total project period was changed from 5 years to 6 years. Chosen as the demonstration site was the Asahi substation in Yokohama. Based on the analysis of the network conditions of the demonstration site, specifications of the HTS cable system were determined. Element technologies were developed and various preliminary tests using short core samples were conducted to confirm the HTS cable design. A 30-meter HTS cable system was manufactured and tested prior to initial demonstration tests. Long-term demonstration tests of the HTS cable system in an actual grid at the Asahi substation are scheduled to be started in 2011.

Modeling of a 22.9 kV 50 MVA superconducting power cable based on PSCAD/EMTDC for application to the Icheon substation in Korea

Two projects for high temperature superconducting (HTS) power cable have been carried out in Korea since 2001. One of them is a HTS cable project in DAPAS (Development of Advanced Power system by Applied Superconductivity technologies) program funded by the Ministry of Education, Science and Technology. In this project, LS Cable Ltd. (LSC) and Korea Electrotechnology Research Institute (KERI) jointly developed a 22.9kV, 50MVA, 3phase, 100m HTS cable using first generation (1G) HTS wire in 2006. The HTS cable system has been tested in a power test center of Korea Electric Power Corporation (KEPCO). LSC and KEPCO have been developing a 22.9kV, 50MVA, 3phase, 500m HTS cable system using second generation (2G) HTS wire since 2008, based on the technology of the DAPAS project. This project is called as GENI (Green Superconducting Electric Power Network at the Icheon Substation) project. The target of GENI project is to install and operate the HTS cable system in the Icheon substation located in near Seoul. In order to analyze the Icheon substation power system employing the HTS cable, an analysis model of the HTS cable is necessary. This paper describes the development of an analysis model for the 22.9kV, 50MVA HTS cable that will be applied to the Icheon substation in Korea.

초전도케이블이 병입된 계통의 고장에 대한 보호협조 검토기법

This paper proposes a coordinative protection study results of 22.9kV HTS(High-Temperature Superconducting) cable implemented distribution system. HTS cable can provide about 5 times larger transfer capacability compare to conventional XLPE cable, however, it has different heat characteristic so called quench. This paper presents the simulation results on Ichun substation HTS cable which connects main transformer and 22.9kV bus. Various expected fault cases are considered and discussed to examine whether conventional protection scheme is effective to protect both of existing facilities and HTS cable. With the results of simulation, conventional protection scheme can be used if instantaneous element and time inverse elements could be adjusted with proper time coordination. Internal temperatures of HTS cable conductor in safe region with proper protection without quench. This results are to be demonstrated by the field test and will be implemented in Ichon substation HTS cable protection and control system.

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.

Results of KEPCO HTS cable system tests and design of hybrid cryogenic system

In order to investigate the compatibility as a power utility facility, Korea Electric Power Corporation (KEPCO) had installed a 22.9kV, 1250A, 100m long high temperature superconducting (HTS) power cable system. Using the HTS cable, various tests have been performed to investigate electrical and thermo-mechanical properties. Since 2005, a series of thermal cycle tests between liquid nitrogen (LN2) and ambient temperatures have been conducted using a vacuum-pump driven open-loop cryogenic system with a capacity of 3kW. In the tests, although the open-loop cryogenic system was reliable to operate the HTS cable system, it was not effective in economic view point because LN2 consumption was larger than expected. In order to secure against unexpected emergencies and solve the problem of LN2 consumption, a hybrid cryogenic system was designed and installed. A stirling cryocooler was employed and combined with the open-loop cryogenic system. Considering the average heat load at rated condition, the cooling capacity of the cryocooler was determined to 4kW at 77K. In this paper, results of performance tests and the design of the hybrid cooling system are presented.