Meng Song

Development of a Leakage Flux-Controlled Reactor

In order to flexibly compensate reactive power, it is necessary to develop a controllable reactor in long distance and ultrahigh voltage system. A leakage flux-controlled reactor (LFCR) is developed in this paper. The operation principles of LFCR are discussed in detail, and a 380 V single-phase LFCR prototype is developed. Relevant experiments have been done to test its performance. The results of the experiments indicate that LFCR has no harmonic and the reactance of LFCR is stable. Also, LFCR with two control windings can realize four kinds of reactance adjustment rates: 1.94%, 75.99%, 90.53%, and 99.05%.

Electromagnetic Characteristics Analysis of Air-Core Transformer Used in Voltage Compensation Type Active SFCL

The three-phase voltage compensation type active superconducting fault current limiter (SFCL) is composed of three air-core superconducting transformers and a three-phase four-wire PWM converter. The primary winding of the air-core superconducting transformer is in series with AC main circuit, and the second winding is connected with the PWM converter. The electromagnetic condition in the transformer can be changed by the compensating current offered by the PWM converter. In this paper, the electromagnetic characteristics of the single phase air-core transformer are calculated by the circuit-field coupled time-stepping finite-element method. The magnitude of the magnetic field and current, phase difference between magnetic fields and current and loss characteristic under different compensating current are studied. The analysis results are very important for the establishment of the control strategy and the transformers design in the engineering realization.

Evaluation of Three Designs for a 35-kV Class Superconducting Reactor

With the expansion of the grid, continuous reactive power compensation is vital for efficient operation of long transmission power lines or cables. Yunnan Electric Power Grid Company is planning to develop superconducting controllable reactors for 500-kV long-distance ac transmission lines. As the second stage of the development plan, a 35-kV class superconducting reactor will be designed and verified by experiments. In this paper, three design proposals, including the racetrack-core type, the three-limb-core type, and the D-core type, for the 35-kV class superconducting reactor are given. Then, their technical and economic feasibility is evaluated. This paper shows that the racetrack-core saturable reactor is a good choice from a technical and economic point of view.

Feasibility Research on Improving the Pulsed Current Output of Superconducting Inductor by Using HTS Air-Core Transformer

This paper aims to study the feasibility of improving pulsed current output by using High temperature superconducting (HTS) air-core transformer. Based on the theoretical analysis, the simulations are done. Results of the simulations indicate that the HTS air-core pulse transformer can magnify the output current magnitude and accelerate the velocity of discharge. However, when a series of inductor modules use the same one HTS air-core transformer, the residual current may influence the discharging waveform. To eliminate residual current, self-coupling discharging model is proposed. The simulated and experimental results illustrate that a self-coupling model can eliminate the residual current effectively. The results of this analysis contribute to the research of superconducting inductor pulsed current output.

Research on the Inductance Variation of Bi2223/Ag Magnet

For the magnet used in power apparatus, the inductance is an important parameter which may change the input-output characteristic of the apparatus. In research of the high temperature superconducting (HTS) magnet in energy storage system and other electric apparatus, we found the difference of the magnets inductance between normal state and superconducting state. In this paper, the electromagnetic models of Bi2223/Ag tape and windings are established firstly. Based on the simulation analysis and measured results, the reason of inductance variation of HTS magnet has been clarified. The regularity of inductance variation of HTS pancake and magnet has been researched, and new requirement for the veracity in the process of superconducting magnets design has been claimed.

AC and Impulse Dielectric Strength of Polymer Materials Under Tensile Stress at 77 K

The performance of dielectric materials has an important effect on influencing the service life of the electric equipments. The dielectric sheets used for superconducting devices usually endure several lapping tension when lapped on the conductor, so the AC and impulse dielectric strengths of polymer sheets under tensile status are important to dielectric design. In this paper, a special electrode system was designed to measure the AC and impulse breakdown voltages of polyimide and poly tetra fluoro ethylene (PTFE) sheets under tensile status both in air at normal temperature and in liquid nitrogen at 77 K. The test data are processed by the method of Weibull plot. As a result, the AC dielectric strengths of polyimide sheets in liquid nitrogen at 77 K increase significantly as the tensile stresses increasing, the most amplitude achieves 29.16%. The impulse dielectric strengths of two polymer sheets all decrease little as the tensile stresses increasing. The AC and impulse dielectric strengths of polyimide under tensile stress are significantly higher than PTFE in liquid nitrogen at 77 K, Polyimide has good dielectric characteristics under tensile status in liquid nitrogen at 77 K.

Dielectric Characteristics of Laminated Paper and Polymer Sheets Used for Lapping Dielectric Structure at 77 K

110 kV cold dielectric high temperature superconducting (HTS) cable has been developing in China. Generally, the lapped dielectric structure is adapted for cable body, so dielectric characteristics of dielectric sheets are very important. Polyimide, Polypropylene laminated paper (PPLP) and polyimide and poly tetra fluoro ethylene (PTFE) are widespread dielectric sheet materials for HTS equipments with lapped structure. In this paper, the lightning impulse dielectric strengths of three materials under tensile statuses are tested by a special electrode system. The experimental results are processed by method of Weibull plot. As a result, the impulse dielectric strengths of all three materials have good adaptive capacity for tensile stresses in liquid nitrogen. The impulse dielectric strengths of polyimide are highest of three materials under normal using stresses. The AC dielectric strengths of three materials are also concluded from previous papers. Combining experimental results, data in previous papers and design methods related, the multi-layered dielectric thickness and layers of PPLP used for 110 kV cold dielectric HTS cable body are designed.

AC dielectric strength of polymer materials under tensile stress at 77K and normal temperature

The performance of dielectric materials has an important effect on influencing the service life of the electric equipments. The dielectric sheets used for superconducting devices usually endure several lapping tension when lapped on the conductor, so the AC dielectric strengths of polymer sheets under tensile status are important to dielectric design. In this paper, a special electrode system was designed to measure the breakdown voltages of polyimide and poly tetra fluoro ethylene (PTFE) sheets under tensile status both in air at normal temperature and in liquid nitrogen at 77 K. The test data are processed by the method of Weibull plot. As a result, the AC breakdown strengths of polyimide films in liquid nitrogen at 77 K increase significantly as the tensile stresses increasing, the most amplitude achieves 29.16%. The breakdown strengths of polyimide under tensile stress are significantly higher than PTFE in liquid nitrogen at 77 K, the most increasing amplitude achieves 121.43%. Polyimide has good dielectric characteristics under tensile status in liquid nitrogen at 77 K.

Lapping dielectric design of 110 kV HTS cable body

High temperature superconducting (HTS) cable is developing towards the direction of bigger capacity and higher voltage grade, 110 kV cold dielectric HTS cable has being developed in China. Polypropylene laminated paper (PPLP) is a widespread used film dielectric material for cold dielectric HTS cable, it is usually lapped on the conductor. So the dielectric characteristics may be effected by the lapping tension. In this paper, the lightning impulse dielectric breakdown strength of PPLP under tensile status is tested by a special electrode system. The experimental results are processed by method of Weibull plot. The impulse dielectric breakdown strengths of 0.1 % breakdown probability under different tensile stresses are achieved. Combining experimental results and design methods related, the lapping thickness and layers of PPLP used for 110 kV cold dielectric HTS cable are designed.

Experimental research on pulse forming based on high-temperature SMES applied in pulsed power

To research the key problems of storage energy and pulse forming in pulsed power, a pulse magnet made of Bi2223/Ag high-temperature superconducting (HTS) tapes applied in pulsed power experiment was developed. After determining electromagnetic characteristics of the magnet, a pulse forming network was designed. HTS magnet was immersed in liquid nitrogen bath, experiments were carried out about discharging pulse current to resistance load based on HTS magnet energy storage (SMES). The results show that pulse current waves were obtained through adjusted circuit construction and magnet parameters by acting delay of switches in the pulse forming network. The technical schemes about pulse forming based on SMES were presented.