Linghui Gong

Development and Test of 10.5 kV/1.5 kA HTS Fault Current Limiter

Superconducting Fault Current Limiter (SFCL) is an attractive appliance for modern electrical power system. A 10.5kV/1.5 kA three-phase HTS fault current limiter was developed by IEE, CAS. This improved rectifier-type SFCL with HTS coil of 6.25 mH is going on a demonstrated long-term reliable operation in a real 10.5 kV substation located in Hunan, China. In a three-phase-to-ground short circuit test of grid, the prospective fault current of 3.5 kA was limited to 635 A at the pre-setup short-circuit point successfully

An apparatus for measurements of thermal conductivity and thermal expansion based on GM cryocooler

The thermophysical properties of matters are extremely important for engineering and materials science. This paper describes a multifunctional apparatus based on GM cryocooler for measurement of thermal conductivity and thermal expansion via steady-state longitudinal heat flow method and strain gauge technique respectively. The apparatus consists of a removable sample test rod on which bulk samples can easily be mounted and placed in the measurement device. Besides, the sample holder is easy to be replaced so that it suits various needs. All measurements are efficiently and accurately carried out at different temperatures by following a set of stability criteria the setup of the apparatus has been calibrated with sample stainless steel and copper, which gives an error within 6% around the published results in the literatures.

Field Test and Demonstrated Operation of 10.5 kV/1.5 kA HTS Fault Current Limiter

Superconducting fault current limiter (SFCL) is an attractive appliance for modern electrical power system. Institute of Electrical Engineering (IEE) at the Chinese Academy of Science (CAS) has successfully demonstrated a three-phase HTS bridge-type fault current limiter (FLC) at a substation in Hunan, China. The FCL suppressed the fault current below 635 A successfully in a 3-phase-to-ground short-circuit field test. Since August 2005, it has been going on a demonstrated long-term reliable operation for one year in the live 110 kV/10.5 kV substation.

Dismountable sample holder apparatus for rapid thermal conductivity measurements based on cryocooler

A novel apparatus, based on cryocooler, for rapid thermal conductivity measurements between 8 K and 300 K is presented. It consists of a removable sample test bar on which bulk samples can easily be mounted and then placed in the described measurement device. This fast mounting measurement system uses a standard steady-state absolute thermal conductivity measurement and allows for excellent thermal stability and mechanical vibration isolation from the cryocooler. The distinction of this system is rapid mounting and measurement of thermal conductivity with high accuracy and precision in data acquisition. In addition, this system allows for versatility in its use, such as the specific heat and the linear thermal expansion measurement. The design of this apparatus, measurement specification, and thermal conductivity of standard materials measured in this system are presented.

LOW TEMPERATURE THERMOELECTRIC PROPERTIES OF Bi‐Sb ALLOYS WITH PARTIAL SUBSTITUTION OF Ag OR Zn FOR Sb

Bi‐Sb‐Ag and Bi‐Sb‐Zn alloys with the general formula of Bi85Sb15−xAgx(x = 0, 1, 3, 5, 7) and Bi85Sb15−xZnx(x = 1, 3, 5, 7), respectively, were prepared by mechanical alloying and subsequent pressure‐less sintering. The phase structures of the samples were investigated by X‐ray diffraction. Thermoelectric properties were investigated by measuring electrical conductivity, Seebeck coefficient and thermal conductivity in the temperature range of 80–300 K. The results show that the figure‐of‐merit of sample Bi85Sb14Ag1 reach a maximum value of 2.16×10−3 K−1 at 219 K, which is twice as large as that of the reference sample Bi85Sb15. The value of 1.58×10−3 K−1 for figure‐of‐merit was obtained in the sample Bi85Sb14Zn1 at 155 K, which is about 78 percent larger than that of the reference sample Bi85Sb15 at the same temperature. The maximum figure‐of‐merit value is obviously shifted towards lower temperature region.

Dynamic simulation of one-stage G-M refrigerator and comparison with experiment

In this paper a mathematical model of a one-stage G-M refrigerator has been made to simulate its dynamic performance. A set of governing equations has been solved by a numerical method. Some P-V diagrams under different refrigeration temperatures have been tested. The calculated results show good agreement with experiment, especially in the hot chamber. The greatest deviation in the cold chamber is about 11%.

Investigation of breakthrough curve of 10K cryogenic adsorber in helium refrigerator

High pure quality helium is required in helium refrigerator and cryogenic adsorber is essential in cryogenic engineering system, while there is a lack of cryogenic adsorption data below 20K which causes inconvenience when it comes to the design of cryogenic adsorber. The paper mainly deals with the design of a 10K cryogenic adsorber in a helium refrigerator which works at 250W@4.5K. Isothermal and nonlinear dispersion plug flow model is built to investigate the breakthrough curve of trace hydrogen with helium being the carrier gas. It can help in lateral design of cryogenic adsorber.

An approach for measuring the thermal conductivity of in situ foamed insulated pipe transporting liquid nitrogen

The thermal conductivity of three foamed pipes has been tested for the development of liquid nitrogen transmission pipelines. By establishing a function between evaporation rate and thermal conductivity, we obtain effective thermal conductivity without destroying pipes. The comparison between our test and test coupons shows that this test device is reliable and could be a standard test for checking insulation properties of in situ foamed pipes transporting liquid nitrogen. The scientific principles, system design, experimental results and effect factors of the test are presented in this paper.

Numerical Analysis and Experimental Study on Natural Convection in the Sample Enclosure Cooled by a G‐M Refrigerator

A double‐stage G‐M refrigerator is used to cool a material sample of about 1 cm3 to low temperature (below 20 K). The sample is cooled by natural convection of helium gas filled in an outer tube, which is connected to the cold heads of a refrigerator through thermal bridges made of pure copper. Some magnetic parameters of the sample at low temperature can be obtained with a Vibrating Sample Magnetometer (VSM). A numerical simulation is used to model the temperature contour in the wall of the sample enclosure, and enable an investigation into the effect of using either copper or nylon for the sample enclosure. At the same time, the simulation and the experimental results are analyzed for further development.