Laminated Paper Composite Insulation System Research Articles

Progress of 275 kV–3 kA YBCO HTS cable

A 275kV–3kA high temperature superconducting (HTS) cable has been developed in the Materials & Power Applications of Coated Conductors (M-PACC) project.AC loss reduction of a two-layer HTS conductor was undertaken by removing the edges of YBCO tapes with low critical current density. The HTS conductor using these tapes was fabricated, and low loss of 0.235W/m at 3kArms was achieved.The 275kV–3kA cable was designed, and the 2m model cables were fabricated. This cable had 325mm2 copper stranded former inside the HTS conductor and a 310mm2 copper shield layer on the HTS shield layer for over-current protection. These cables withstood an over-current of 63.0kA for 0.6s, which is the worst situation for 275kV systems.The partial discharge (PD) and V–t characteristics of a liquid nitrogen (LN2)/polypropylene (PP) laminated paper composite insulation system have been integrated into the design of the insulation for the 275kV cable. The results revealed that the PD inception stress (PDIE) did not depend on the insulation thickness, and that lifetime indices of V–t characteristics at PD inception were as high as about 80–100.

Partial discharge activity in electrical insulation for high temperature superconducting (HTS) cables

This paper discusses electrical insulation characteristics of liquid nitrogen (LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) / polypropylene (PP) laminated paper composite insulation system for the practical electrical insulation design of high temperature superconducting (HTS) cables. Partial discharge (PD) inception, propagation and breakdown (BD) characteristics under ac voltage application were obtained and discussed at atmospheric and pressurized conditions. Experimental results were analyzed quantitatively and revealed that void- type discharge was categorized as an important form of discharge to characterize the transition of PD activity leading to BD.

Impulse and ac partial discharge inception and breakdown characteristics of LN2/polypropylene laminated paper composite insulation system

Partial discharge (PD) inception and breakdown (BD) characteristics of liquid nitrogen (LN2)/polypropylene (PP) laminated paper composite insulation system for high temperature superconducting (HTS) cables are presented. In this paper, we measured PD inception characteristics under lightning impulse and AC voltage applications by electrical, optical and acoustic methods. The impulse PD inception characteristics were compared with those under AC voltage application, and the PD generation mechanisms are discussed. Experimental results reveal that PD detection sensitivity under lightning impulse voltage application is as small as 6 pC. PD inception at the lower stress was verified to be generated not only in the butt gaps but also in micro gaps between PP laminated paper layers under both lightning impulse and AC voltage applications. After PD inception, PD activity could be developed in the butt gaps at the higher stress, finally leading to BD

A novel technique for partial discharge and breakdown investigation based on current pulse waveform analysis

A novel technique for partial discharge (PD) measurement and analysis (PD-CPWA; PD current pulse waveform analysis) is developed and introduced in this paper. PD-CPWA is expected to be utilized to discuss PD mechanisms and physics in electrical insulating materials, focusing on the PD current pulse waveform and its time transition from PD inception to breakdown (BD). In this paper, the concept and principle of PD-CPWA are described, and the applications of PD-CPWA to (1) epoxy spacer samples under thermal and electric combined stresses in GIS, (2) creepage PD on epoxy spacers in SF/sub 6/ gas and (3) liquid nitrogen/polypropylene laminated paper composite insulation system for high temperature superconducting cables are introduced and discussed.

Dielectric Characteristics of HTS Cables Based on Partial Discharge Measurement

We have discussed dielectric characteristics of liquid nitrogen (LN/sub 2/)/polypropylene (PP) laminated paper composite insulation system for the practical electrical insulation design of high temperature superconducting (HTS) cables. Focusing on the partial discharge (PD) inception characteristics and mechanism, the volume effect and its saturation on PD inception electric field strength (PDIE) was evaluated at atmospheric and pressurized condition. PD inception characteristics under lightning impulse voltage application were also investigated using an electrical and optical PD measuring system, and compared with those under ac voltage application.

Research on Insulation Design of 22.9-kV High-&amp;lt;tex&amp;gt;$rm T_rm c$&amp;lt;/tex&amp;gt;Superconducting Cable in Korea

The electrical insulation design is important for high-Tc superconducting (HTS) cable because the cable is operated in a medium voltage environment. For the insulation design of HTS cable, it is necessary to investigate the ac, impulse breakdown, and partial discharge inception stress of a liquid nitrogen/polypropylene laminated paper composite insulation system. These results were used to design the electrical insulation of 22.9-kV-class HTS cable in Korea and cable was manufactured. A manufactured mini-model HTS cable was evaluated for ac withstand voltage, impulse withstand voltage, breakdown and dielectric tangent loss (tan/spl delta/). From these tests, the cable has satisfied the standard technical specification of KEPCO in Korea. The breakdown voltage was 110 kV.

Partial discharge inception characteristics of LN/sub 2// polypropylene laminated paper composite insulation system for high temperature superconducting cables

Partial discharge (PD) inception characteristics of liquid nitrogen (LN2)/polypropylene (PP) laminated paper composite insulation system for high temperature superconducting (HTS) cables were investigated in terms of the volume effect and the V-t characteristics. The electrical and optical measurements of PD inception characteristics showed that initial PD could be generated between PP laminated paper layers, as well as in a butt gap. Using a parameter called statistically stressed liquid volume (SSLV) based on the discharge probability in both butt gaps and LN2-filled thin layers between PP laminated papers, we could systematically analyze and evaluate the volume effect on PD inception stress (PDIE). Furthermore, experimental results revealed that n values of V-t characteristics at PD inception were as high as 80-110. On the other hand, the lower n values obtained at breakdown were interpreted by the intensified PD development in thermal bubbles generated after the PD inception