Stability Margin Analysis Of Cold Dielectric High Temperature Superconducting Cable

ABSTRACT:Compared with the conventional cable, the high temperature superconducting (HTS) cable can improve3to5times transmission capacity and reduce10times transmission loss. It has the advantage of large transmission capacity, low loss, small volume, light weight, and no environmental pollution. It can greatly improve the power grid transmission capacity and reduce power loss by using HTS cable to built transmission backbone power grid. Because of the large transmission capacity, it is always used as a backbone transmission power in the power grid. Once fault appears, not only the reliability of the electricity supply regions is affected, but also the HTS cable may be burnt, which can influence the stability of the whole power system. Therefore, the stability of HTS cable under fault is the key technology to promote the practical process of HTS cable.This thesis studied the current and temperature distribution of110kV/3kA HTS cable under refrigeration system failure and large fault current, calculated the stability margin of HTS cable under different fault conditions. First of all, based on the structure of second generation HTS tape, the mathematical model of AMSC tape is established. According to the structure of cold dielectric high temperature superconducting (CD HTS) cable, the mathematical model of HTS cable is established, the self inductance and mutual inductance of HTS cable conductor layer are calculated. This thesis proposed the method for calculating the equivalent resistance of HTS cable each layer. The heat transfer model of HTS cable is analysed, the convective heat transfer coefficient between HTS cable and liquid nitrogen is calculated. Based on MATLAB and ANSYS software, the HTS cable magnetic-thermal coupling model and heat conduction model are built, the MATLAB calculation flowchart of HTS cable under fault current are introduced.Secondly, this thesis carried on theoretical analysis at the stability of superconductor, calculated the current distribution within the HTS cable conductor layer1under fault current.The safe operating temperature range of HTS cable is proposed under refrigeration system fault and liquid nitrogen stops flowing. The thesis calculated the temperature distribution of each layer at the entrance and exit of LN2, the temperature margin of HTS cable is given under different fault time and fault current.Finally, according to the structure parameters of HTS cable, the author manufactured a0.3m long HTS cable for the cable test. The joint resistance, experiment scheme of critical current test and large current impact test are designed, The current distribution of conductor layers and copper frame under different fault current are analyzed.The correctness of the theoretical calculation model used in this thesis is verified by comparing the theoretical and experimental results.