The electrical measurement of AC losses in a three-phase tri-axial superconducting cable

Abstract

In a three-phase tri-axial cable, the magnetic interaction between the phases makes the loss measurement by an electromagnetic method very complex. We developed the theoretical background showing that three-phase AC loss measurements by the electromagnetic method are, in principle, possible. We then implemented this theory in practical measurements on a 3 m long, tri-axial cable fabricated from RABiTS (rolling-assisted biaxially textured substrate) coated conductor. Initially, the proposed measurement technique was implemented in the simpler cases when the three cable phases are 180 • out of phase, i.e. (0 • , 180 • , 360 • ) or (0 • , 360 • , 180 • ) rather than (0 • , 120 • , 240 • ) as in a traditional three-phase system. For these cases, the currents in the phases are either in phase (360 • phase difference) or anti-phase (180 • phase difference). These are essentially single-phase measurements with only one transport current used as the supply for all three phases. This simplification allowed us to use both the established and the proposed techniques to measure the total losses of the cable for these cases. An excellent agreement between the two measurement methods confirmed the validation of our proposed measurement technique. The proposed measurement method was then employed to measure the total AC losses in a cable when it operates in the true three-phase mode. We believe that these data represent the first electromagnetic three-phase AC loss measurements.

New Experimental Method for Investigating AC Losses in Concentric HTS Power Cables

“…An electric determination in both cases is prohibited, since the positioning of voltage leads inside the cryostat are not desired in the HV-environment. Moreover, the electric evaluation of AC-losses is particularly difficult in a three phase coaxial cable [4] as Ampacity. The magnetic fields at the surfaces of the tapes have axial and azimuthal components caused by the three independent currents.…”

“…Moreover, the electric evaluation of ac losses is particularly difficult in a three-phase coaxial cable [4] as Ampacity. The magnetic fields at the surfaces of the tapes have axial and azimuthal components caused by the three independent currents.…”

Performance Analysis of Real-Scale 23 kV/60 MVA Class Tri-Axial HTS Power Cable for Real-Grid Application in Korea

“…The current distribution in each phase and layer is determined by the iterative calculation of the impedance matrix of Equation (3) with a combination of pitch length and winding direction. The iterative calculation of the impedance matrix is performed by applying an impedance matching algorithm that satisfies the set current value in each layer, and Figure 3 shows a flow chart of the impedance matching method [15,16].…”