Development of a termination for the 77 kV-class high Tc superconducting power cable

Abstract

A termination for 77kV-class high Tc superconducting power cables was designed and fabricated. The termination is insulated with SF6 gas, nitrogen gas and liquid nitrogen and is cooled withi liquid nitrogen. The current lead has a cross sectional area altered along its axis in order to decrease the heat inlet and to prevent SF6 gas from liquefying. The current lead is insulated with Ethylene-propylene Rubber (EPR) because it passes through nitrogen gas which has low dielectric strength in comparison with liquid nitrogen and SF6 gas. 200A AC current and 70kV AC voltage to ground were successfully applied simultaneously for 40 hours in total. The measured heat loss of the termhation, 19W, is in good agreement with the calculated value. As the next step, the applied voltage was increased and the termination was confirmed to withstand the voltage up to 12OkV AC and 4OOkV Imp to ground.

Calculation of Alternating Current Distribution on the Current Lead for HTS Power Cable

“…The magnitude of the current density falls off exponentially from the surface. When the magnitude falls to 1/e of its surface value, the distance from the surface is called as skin depth [6] and expressed by (2) where is permeability (H/m) representing the easiness of the magnetic field formation in the material, and is frequency (rad/s) of the current.…”

“…The other heat loads entering the liquid nitrogen chamber are radiation from vacuum insulated cryostat and conduction between vacuum cryostat and liquid nitrogen chamber through supports. Since the heat loads through current lead are the major parts of the total heat loads generated in the termination cryostat, reducing the heat loads on the current leads plays an important role for the optimal design of the current leads [2], [3]. In this paper, the effect of AC on the design of the current leads of the termination of the HTS transmission cable system was investigated.…”

Comparative study of high voltage bushing designs suitable for apparatus containing cryogenic helium gas

“…Other researchers have reported using some novel techniques in designing bushings for high temperature superconducting (HTS) cables. In one case they had transitioned from liquid nitrogen (77 K) to ambient by traversing through two gaseous chambers, one with cold gaseous nitrogen and the next, being SF 6 [4]. The other case was similar in construction where the transition was by going through two chambers with cold gaseous nitrogen and finally warm nitrogen [5].…”

The Electrical Insulation Characteristics for a HTS Cable Termination

“…With this insulation system, there are the occurring of discharge on the surface of solid insulator and breakdown in the or . The HTS cable termination is developing elsewhere in the world, recently [1], [2]. In Korea, KERI and LS cable are developing 154 kV class HTS power cable, so the study on breakdown characteristic of insulators to make the basic knowledge and data for insulation design of the termination for the 154 kV class HTS cable is essential.…”