General approach for the determination of the magneto-angular dependence of the critical current of YBCO coated conductors

Geng

Shen

et al. 2018

J Supercond Nov Magn

The application of resistive-type superconducting fault current limiters (RSFCLs) in electrical networks is very attractive due to their relative compactness, light weight, and good performance. However, this technology still has drawbacks: asymmetrical quench, uncertain limiting velocity, passive action and incapability of enlarging capacity. Here, we present an active quenching technique which can potentially solve these problems. The quenching process is triggered using highfrequency (HF) AC fields, which are generated by two coupled copper coils attached on both sides of the YBCO sample. Our experiments show that this approach is effective in guaranteeing uniform quench and therefore is expected to be able to significantly extend the service life of the device. Moreover, the quench speed can be considerably increased by the HF field. We find that the performance of acceleration is positively correlated to the transport current, intensity and frequency of the AC field. In addition, a DC magnetic field is added around the sample holder simultaneously with the AC field, to study the field-angular-frequency dependence of the quench time t (B AC f AC B DC θ DC ). Experimental results prove that the DC magnetic field can cooperate with the HF AC field to accelerate quench, which means better performance can be produced with lower costs with the two fields acting together. In all, this technique showed outstanding performance regarding quench acceleration and tape protection. We believe the HF-assisted quenching technology has a promising future in current-limiting devices and hope our findings could be helpful for its potential applications.

Section: Study Of Active Quench Under Various External DC Fieldssupporting

confidence: 79%

“…In our previous research, we had generalized a fitting function which was capable of accurately describing I c (θB) relationship of 2G HTS tapes [29]:…”

Section: Field-angular Dependence Of the Critical Current Of The Studmentioning

confidence: 99%

Active Quenching Technique for YBCO Tapes: Quench Acceleration and Protection

Geng

Shen

et al. 2018

J Supercond Nov Magn

“…The equation we derived is an extended version of the Kim model [16], which takes into account the material anisotropy and the flux-creep processes of YBCO samples [10]. Our approach can be generalized as…”

Section: Curve Fittingmentioning

confidence: 99%

“…To solve this problem, previously, we have measured the magneto-angular dependence of critical current density of five different YBCO commercial tapes [10]. During the fitting process of these results, the validity of our novel multi-objective model was successfully proved.…”

Section: Introductionmentioning

confidence: 98%

Study of Critical Current and n-Values of 2G HTS Tapes: Their Magnetic Field-Angular Dependence

Zhong

Geng

et al. 2018

J Supercond Nov Magn

Since many applications of YBCO tapes operate in external magnetic fields, it is necessary to investigate the magnetoangular dependence of critical current and n-values in coated conductors. In this paper, five commercial YBCO tapes with different microstructures produced by three different manufacturers are chosen. The selected samples have a width of 2.0, 4.0, 4.8, 6.0 or 12 mm, with copper, brass or stainless steel laminations. The critical current density dependence J c (B, θ) and n-values characteristics n(B, θ) of the tapes are comprehensively measured under various magnetic fields and orientations. Afterwards, the obtained experimental data sets are successfully fitted using a novel multi-objective model which considers the material anisotropy. By using this approach, a fitting function I c (B, θ) can always be obtained to accurately describe the experimental data, regardless of the fabrication and width differences of the superconducting tapes. Moreover, our experiment shows that when subject to different external magnetic fields, the angular dependence of n-values characteristics is directly correlated with the corresponding critical current profiles. Our results are helpful to predict the critical current of electromagnetically interacting 2G HTS wires, thereby improving the design and performance of the devices made from YBCO tapes.

“…For the design of the HTS transformer, the critical current of the second generation coated conductor is about 300 A/cm at 77 K [9]. The perpendicular component of the magnetic field at the coil ends is estimated to be 0.18 T, which could reduce the critical current of the second generation (2G) HTS tapes to 200 A/cm.…”

Section: Introductionmentioning

confidence: 99%

Effectiveness of Superconducting Fault Current Limiting Transformers in Power Systems

Elshiekh

IEEE Trans. Appl. Supercond.

Ravindra

et al. 2018

Abstract-Superconducting devices have emerged in many applications during the last few decades. They offer many advantages including high efficiency, compact size, and superior performance. However, the main drawback of these devices is the high cost. An option to reduce the high cost and improve the costbenefit ratio is to integrate two functions into one device. This paper presents the superconducting fault current limiting transformer (SFCLT) as a superior alternative to normal power transformers. The transformer has superconducting windings and also provides fault current limiting capability to reduce high fault currents. The SFCLT is tested in two power system models: a 7 bus wind farm based model simulated in PSCAD and on the 80 bus simplified Australian power system model simulated in RTDS. Various conditions were studied to investigate the effectiveness of the fault current limiting transformer.  Index Terms-Transformers, superconducting, fault current limiters .