Current and Voltage Distribution Analysis of Control Winding in a 35-kV HTS-CR Considering AC Losses

A 35-kV/100-A high-temperature superconducting controllable reactor (HTS-CR) is under development based on the principle of adjusting the main magnetic flux density and the length of magnetic circuit. The control winding of the HTS-CR is made up of double pancakes (DPCs) that are wound with HTS tapes. In order to increase the current margin of HTS winding, a four-tape bundle conductor is adopted in DPCs. Although tape transportation is utilized to balance the inductance, the current of each parallel conductor should be calculated to get the critical current. In particular, the ac losses caused by the high leakage of flux density on HTS tapes may aggravate imbalance of current and voltage distribution. This paper builds the equivalent circuit model of the parallel conductor and calculates the distribution characteristic of ac losses. Current redistribution has been analyzed by importing the equivalent resistance. Meanwhile, voltages of parallel inductance have been detected to acquire a more intuitive reference, which will provide a basis and support for quench detection and protection.