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Because of the small square dimension, a solderedstacked-square (3S) high-temperature superconducting (HTS) wire with 1 mm width is considered as a candidate for cabling large current conductors through twist process. For studying the twist structure, in this work, we prepared several twisted 3S wire samples fabricated from the same piece of the 3S wire with 10 m length. For the 3S wire, the uniformity of critical current was evaluated. As well, we investigated basic electrical and mechanical characteristics for the twisted 3S wire. The main results show that the critical current distribution for the 3S wire is relatively uniform at the average value of 90 A; the allowable minimum twist pitch of the twisted 3S wire is about 60 mm; the critical current of the twisted 3S wire shows isotropy characteristics; through the test for frequency dependence of self-field loss, we can know the eddy-current loss in the twisted 3S wire can be ignored, and the measured losses are identical to the calculated one fromthe thin strip equation; the minimum bending diameter and allowable tensile force for the twisted 3S wire are approximately 80 mm and 400 N, respectively. [ABSTRACT FROM AUTHOR]

The Bi-2212 monofilar bulk element was selected as a candidate in developing a 24 kV/630 A class superconducting fault current limiting (SFCL) system. This study investigated the Bi-2212 monofilar element both experimentally and theoretically regarding the DC voltage-current characteristics, AC loss characteristics, inductance, current limiting characteristics and local temperature distribution. It was found that the critical current of the Bi-2212 monofilar element increased 3.3 times as the operation temperature decreased from 77 K to 65 K. Although the arrangement of the Bi-2212 conductor was a coil shape, the measured AC loss was at a level similar to what is calculated from the Norris equation at both the temperatures 77 K and 65 K. The temperatures measured at each section during a fault were in good agreement with the results of the numerical analysis. Moreover, the results showed that the monofilar element was not yet sufficiently homogeneous to be used at its full rated voltage. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Direct sequence code division multiple access (DS-CDMA) and orthogonal frequency division multiplexing (OFDM) systems are two options for broadband power line communications. In this paper, a comparison is made between the CDMA and OFDM systems. The bit error rate (BER) performance and the optimum overall data rate of the CDMA and OFDM systems are analyzed and compared, using the criteria of the same bandwidth occupation, the same transmission power for each user, the same total number of users in the system and the same power line channel. The comparison is based on the analytical models that are developed and verified by simulations. [ABSTRACT FROM AUTHOR]

The high-temperature superconductor (HTS) with large current capacity has been developed for power applications such as power transmission cables and fault current limiters. Especially, in these power applications, AC loss is very important in an economic point of view but this issue has not been completely elucidated due to its many complexities. In this work, two HTS conductors with very different critical current densities, which consist of several Bi-2223 tapes placed on a cylindrical former, were fabricated in an attempt to arrive at a clear understanding of their AC loss characteristics. AC loss characteristics for such two cylindrical multi-tape conductors have been experimentally investigated. Moreover, the influence of current transport mode on the AC loss of the Bi-2223 tape in the conductors was investigated. DC voltage-current characteristics of the Bi-2223 tapes were also measured for discussions on the measured AC losses. The results show that for the conductor with high critical current density, the measured AC loss strongly depends on the transport mode as in the conductor with low critical current density. However, the transport mode dependence of the conductor with high critical current density becomes weaker and weaker as transport current increases. In the simultaneous mode, the measured AC loss of the conductor with low critical current density is in good agreement with the calculated loss from the monoblock model. However, the measured loss of the conductor with high critical current density does not coincide with both the numerically calculated loss and loss calculated from the monoblock mode. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The impulsive noise and multipath effects are the main reasons to cause bit errors in power line communications. In this paper, the bit error rate (BER) performance of the orthogonal frequency division multiplexing (OFDM) system under the impulsive noise and multipath effects are theoretically analyzed in terms of closed form formulas. Through the analysis, it is shown that OFDM can mitigate the adverse effect of the impulsive noise and only the heavily disturbed impulsive noise will interfere the BER performance of the OFDM system. It is also shown that the adverse effect of multipath is more serious than that of impulsive noise. In this paper, the guard interval is used to improve the BER performance of the OFDM system. As the longer guard interval is inefficient in using the signal power, the optimum guard interval that can achieve the best BER performance is studied. [ABSTRACT FROM PUBLISHER]

This paper presents the development of a power line test bed which provides a platform to simulate the 230 V/50Hz power line environment in a con trolled and reproducible engineering manner. The target is to communicate data over power lines in the frequency range from 1MHz to 10MHz. This test bed is integrated with power line communication (PLC) channel model, loads and impairment devices for worst-case environment simulation. Besides, the methods for coupling and isolating the high frequency signals from one section to another section are discussed. These methods are important for realizing the test bed as the noise immunity, channel impedance controllability, and high frequency communication signal coupling and isolation capabilities are essential. [ABSTRACT FROM AUTHOR]