AC Losses Calculation And Analysis Of The Cold Dielectric High Temperature Superconducting Cable

Cold dielectric(CD) high temperature superconducting (HTS) cable has compact structure, small size, capacity, no electromagnetic pollution and many other advantages. It will realize large-scale application in the future high temperature superconducting transmission field. The AC losses of the HTS cable directly related to the operation cost of the HTS cable and stability. The advantage will be reflected only if the AC loss is low enough compared with the normal conductor power cable. So HTS cable AC loss is one of the most important research topic of power application. It has important significance to establish calculation theory and measurement system for calculating and measuring the AC loss rapidly and accurately.In this paper the critical current characteristics of HTS YBCO tapes are studied by experiment firstly, and its AC loss theory model is given. Then the layer’s current sharing mathematical model and magnetic field distribution model of the CD HTS cable are established based on the structure of the first110kV/3kA CD HTS cable based YBCO2G tapes in China. According to each layer’s current and magnetic field distribution of the HTS cable, considering the critical current degradation rates in alternating magnetic field of each superconductor layer, the AC losses numerical calculation theory of the CD HTS cable is built through two methods. The Matlab software is used in the calculation process. The results showed that calculating results by two methods are in agreement at77K and69K temperature, and the total AC losses have linear relationship with the current frequency. The influence of conductor layer current sharing characteristic on AC losses of the HTS cable is also studied. The results indicates that the uniform layer current distribution gives the minimum total AC losses of the HTS cable is decided by Ip/Ic, Ip is the peak value of the transport current and Ip is the critical current of the HTS cable. When Ip/Ic is small enough the uniform layer current distribution does not give the minimum total AC losses, and the minimum total AC losses can be gained by mean of pitch adjustment to change the distribution of layer’s current and magnetic field. And a new idea to reduce the AC loss of the HTS cable by mean of making the operation current of the HTS cable far away from its critical current.The HTS cable electrical measurement theory and method are researched. And the existing problems of electrical method are put forward. And then the AC loss measurement system of CD HTS cable is set up, error during the measurement is also analyzed and the improvement is put forwardFinally, electrical method is used to measure the AC loss of1.5m demo CD HTS cable and3m four layers Bi HTS cable. The results prove calculation method is correct and also show the electrical method is effective to measure the AC loss of the HTS cable.20cm CD HTS cable is fabricated manually. Its joint resistance is measured in direct current. And the influence of joint resistance on AC loss measuring is eliminated.The results show that under the low frequency the AC loss of The CD HTS cable has a linear relationship with the transport current frequency.