In recent years, great progress has been made in the R&D of the coated conductor technology by which high performance HTS 2G wires can be fabricated. The availability of long length 2G wires makes the applications of these HTS conductors possible for various electric devices. Despite the long lengths of the wires, it is often necessary and sometimes even inevitable to make splice joints between the wires. Splicing of 2G wires is needed during device manufacturing, equipment installation, and/or field repair. To ensure the safe and reliable operation of an HTS device, high quality coated conductor splice joints are required. The most important properties of a splice joint are the current carrying capacity, electrical resistance and mechanical strength. For practical applications, other properties of a splice such as its stability and ac loss characteristics are also important. Due to the differences in architectures and manufacturing techniques of present commercial 2G wires, properties of splices are expected to vary not only with the joint fabrication methods but also with the wires being used. Even for a certain type of wire, the asymmetry of wire structure will also influence the joint characteristics depending on the joining configuration. That is whether the joints are fabricated in face-to-face, back-to-back, or face-to-back configurations as regards to the HTS side and the substrate side of the wire.
The research in the area of coated conductor splicing carried out in our group is part of the ORNLís Advanced Cables & Conductors Program which is sponsored by DOEís Office of Electricity Delivery & Energy Reliability. The purpose of this work is to achieve basic understandings about the splicing processes and on the properties of the splices made by different techniques. The ultimate goal is to develop reproducible, reliable, efficient and cost-effective splicing techniques for making high quality coated conductor splices. The information generated through this work is meant to be useful to both HTS wire manufacturers and HTS device manufacturers in the 2G wire applications. It should be noted that at this stage the work being carried out is primarily on commercial coated conductors with the splice fabrication methods recommended by the wire manufacturers as a starting point. Any departure from the recommended methods is either the result of the feedback from an end-user of 2G wires or from the purpose of simplifying a splice fabrication process.
While soldering is a widely used method for making coated conductor splices, fundamental information regarding the solderability of commercial 2G wires is provided in this website. Splice properties, mainly the electrical resistance and the V-I characteristics, are given for the splices made using the 2G wires manufactured by either American Superconductor (AMSC) or SuperPower Inc. While all the results were obtained from our experiments and the specific 2G wires were used, it was not ORNLís intention to make comparison between different commercial wire products. The selection of the materials does not imply the recommendation or endorsement by ORNL. Nor does it imply they are necessarily the best available for your application.
Electrical resistance of the splices fabricated and tested by ORNL. For each splice, the fabrication conditions including the soldering materials used and soldering temperature are given. A typical resistance value of splices fabricated using a specific 2G wire is provided with the corresponding VI curve.
Solderability testing was carried out based on a standard method. The results showed the solderability of different combination of solder/flux to the commercial coated conductor surfaces.
Contact angles were measured using the sessile method. The contact angle is a fundamental parameter used to evaluate the wettability of a solder/flux system to a given coated conductor surface.
For questions, please contact Yifei Zhang at firstname.lastname@example.org