K. Ryu

Performance Test of 100 m HTS Power Cable System

In order to meet the needs of economical and stable power supply and high current density cable with compact size, several countries carry out researches on high temperature superconducting (HTS) cables. Korea Electric Power Corporation (KEPCO) established the HTS cable test center and installed 22.9 kV, 1250 A, 50 MVA, 100 m class HTS cable system to investigate the performances and application possibility in real power grids. The HTS cable system went through seven cool down and warm-up cycles and also many kinds of performance tests for 3 years. Rated voltage-current tests, over voltage tests, and measurements of heat loss and AC loss with various currents have been examined. Moreover, DC critical current tests were performed for checking conductor degradation before warming up or after cooling down. Through the performance tests of the HTS cable system, the overall efficiency and loss factors are estimated and compared with conventional power cables in this paper. We conclude the present status of HTS cable system and application possibility in the real power grid.

3 MJ/750 kVA SMES System for Improving Power Quality

The purpose of this study is to develop a superconducting magnet energy storage system (SMES), which protects sensitive loads on the power system, when an interruption or voltage sag occurs. Industries have many sensitive machines, and keeping the power in a good condition is very important for nonmilitary machines also. Korea Electrotechnology Research Institute (KERI) has developed a 3 MJ/750 kVA SMES system to improve power quality in sensitive electric loads. It consists of an IGBT based power converter, NbTi mixed matrix Rutherford cable superconducting magnet, and a cryostat with HTS current leads. The operating current of the 3 MJ SMES magnet was 1000 A. The SMES system is tested under short time power interrupt to verify the feasibility of the SMES system as a 750 kVA power converter

Development of a 100 hp synchronous motor with HTS field coils

A 3-phase, 100 hp, 4 pole, 1800 rpm superconducting synchronous motor built and tested in Korea Electrotechnology Research Institute(KERI). This machine consists of HTS rotor and air-core stator. The HTS field windings are composed of the double-pancake coils wound with AMSCs stainless steel-reinforced Bi-2223 tape conductor. These were assembled on the support structure and fixed by a bandage of glass-fiber composite. The cooling system is based on the heat transfer mechanism of the thermosyphon by using GM cryocooler as cooling source. The cold head is in contact with the condenser of a Ne-filled thermosyphon. The rotor assembly was tested independently at the stationary state and combined with stator. The open circuit, no-load, and short circuit characteristic were obtained. Also, load tests in motor mode driven by inverter and generator mode connected to resister load bank were conducted. This paper will present design, construction, and experimental test results of the 100 hp HTS machine.

Influence of tape's critical currents and current distributions on AC loss measurement in a multi-tape conductor

AC loss is an important issue to design high temperature superconductor power cables, which consist of a number of Bi-2223 tapes wound on a former. In the cables, the tapes have intrinsically different critical currents, and they are electrically connected to each other and current leads. This makes loss measurements considerably complex, especially for short samples. In this work, we have prepared a multi-tape conductor composed of Bi-2223 tapes. The ac losses of the conductor have been experimentally investigated. The loss tests indicate that the effect of critical currents of each tape on AC loss measurement in the multi-tape conductor is negligible only if currents in the tapes flow uniformly. Moreover, the measured loss of the conductor is in good agreement with the sum of the transport loss in each tape. However, in the case of nonuniform current distribution, the measured AC loss considerably depends on the current distribution parameter /spl gamma/, and the positioning of a voltage lead. Thus it should be very careful to measure the AC losses in the short power cable samples.

AC transport current loss of horizontally attached Bi-2223/Ag tapes

In this paper we investigate AC-transport current loss and current distribution of Bi-2223/Ag tapes which are arranged in edge-to-edge configuration. A numerical code was developed to estimate the transport current loss and the current distribution across the tapes. AC-loss measurements were also performed and the coincidence between the calculated and measured values is excellent. AC losses of the horizontally-attached tapes were larger than just a simple summation of each tapes loss but not as large as the loss from Norris equation. Discussions on these results are addressed using the current distribution obtained from numerical analysis.

Effect of the neighboring tape's AC currents on transport current loss of a Bi-2223 tape

Bi-2223 tapes have been developed for low-field power applications at liquid nitrogen temperature. When the Bi-2223 tapes are used in an application such as a power transmission cable or a power transformer, they are supplied with an AC transport-current and exposed to an external magnetic field generated by neighboring tapes AC currents simultaneously. AC loss. taking into account such real applications. is a crucial issue for power applications of the Bi-2223 tapes to be feasible. In this paper, the transport losses for different AC current levels and arrangements of the neighboring tapes have been measured in a 1.5 m long Bi-2223 tape. The significant increase of the transport losses due to neighboring tapes AC currents is observed. An increase of the transport losses caused by a decrease of the Bi-2223 tapes critical current is a minor effect. The measured transport losses could not be explained by a dynamic resistance loss based on DC voltage-current characteristics in combination with the neighboring tapes AC currents. The transport losses do not depend on the frequency of the neighboring tapes AC currents but its arrangements in the range of small current especially.

Status of HTS Motor Development for Industrial Applications at KERI & DOOSAN

This work is development of HTS motor at DOOSAN heavy industry and Korea Electrotechnology Research Institute in Korea, and is sponsored by DAPAS program which is supported by Korean government. The final aim of the project is realization of HTS motor in the field of industry such as large driving pumps, fans and compressors for utility and industrial environments. In the first phase (2001-2004), 100 hp HTS motor was developed in order to implement the preliminary technology for the large applicable HTS motor. All of the performance characteristics are well met to the designed ones. In second phase (2004-2007), 1 MW HTS motor is developed for the purpose to fully represent the design and manufacturing issues for the larger capacity machine. The machine is 2 pole and 3600 rpm, and all of the components are completely manufactured. This machine is now under assembly. This paper summarizes the status of 1 MW HTS motor development, such as design, construction, and experimental test results.

A study on the application effects of HTS power cable in Seoul

In this study, we performed the long-term expansion planning for the conceptual design of HTS power cable in Seoul area. In Korea, underground power cable has been required gradually with increasing demand of electric power transmission density and low loss characteristics in the comparison with a conventional power cables, so we assumed that the HTS power cable is applied between the downtown area and the outskirts of the city for the large power transmission capacity. This paper is to show the effects of HTS power cables in Seoul based on the power system analysis.

AC Loss Measurement of a Short HTS Cable With Shield by Electrical Method

In order to electrically investigate the AC losses of the conductor and the shield in an actual HTS cable with shield, we attached two voltage-leads to the conductor and shield of a short cable which is the same as the Korea Electric Power Corporation (KEPCO) HTS cable under the field test, and examined it. The result shows that the polarities of the loss voltages measured from both voltage-leads are opposite. The ratio (1.6) between the losses for different transport periods measured from the conductor-lead is quite large. It is considered from these results that the conductor loss is the sum of the losses measured from the conductor-lead and shield-lead. And this conductor loss corresponds well with the numerical result too. Moreover, the total loss of the short cable measured from the proposed electrical method at 77 K was compared with that of the KEPCO cable by calorimetry at 66.6 K through our numerical model. The difference between the measured losses and numerical ones is almost the same. This means that the shield loss is measured from the shield-lead, and the conductor loss from both voltage-leads.

AC Loss Characteristics of a Cylindrical High Temperature Superconductor

A cylindrical high temperature superconductor (HTS) is often used in power applications such as power transmission cables and matrix fault current limiters. In commercialization of these apparatuses, AC loss is a critical factor but not elucidated completely because of complexities in its measurement, e.g. non-uniform current distribution and phase difference between currents flowing in an individual HTS tape. We have prepared two cylindrical conductors composed of a Bi-2223 tape with different critical current density and one hollow conductor made of Bi-2212 bulk material. In this paper, the AC loss characteristics of the conductors have been experimentally investigated and numerically analysed. The results show that the measured losses for all the conductors are not dependent on both arrangements and contact positions of a voltage lead. This implies that most of loss flux is only in the conductors. The loss for the Bi-2223 conductor with high critical current density is in good agreement with the numerically calculated one based on the polygon model, whereas the loss measured for the Bi-2223 conductor with low critical current density coincides with the calculated loss from the monoblock model.