Abstract: A method of controlling the effective impedance of a low-impedance high-temperature superconducting cable (“HTS cable”). Passive or active control circuitry is used to create a current in the shielding conductor of the HTS cable which opposes the current in the primary conductor. In the case of a three-phase conductor, magnetic cross-coupling between the phases is exploited. The magnitude of the magnetic field is used to alter the HTS cable's effective impedance. The result is the creation of a controlled and substantially-higher effective impedance for the HTS cable. The creation of the higher impedance allows the HTS cable to be connected in parallel with conventional lines while regulating the amount of current flowing through the HTS cable.

Abstract: An electrical device operating on the principle of induction, such as a transformer. The device employs High Temperature Superconductors to build pancake coils having a very low height to diameter ratio. These pancake coils are placed around ferromagnetic core legs as in a conventional transformer. In multiphase applications, the low height to diameter ratio of the pancake coils causes the transformer to become quite wide. The present invention proposes overlapping the adjacent pancake coils in a multiphase induction device to reduce the width. A specific example of a 3-phase power transformer is presented.

Abstract: A cryostat for a superconducting transformer is provided that includes non-conducting load bearing insulation and is adapted for use with a superconducting transformer. In addition, the cryostat prevents the formation of closed loop stray currents on its outer case. The cryostat contains the winding sets and other related electrical equipment of a transformer. The cryostat generally comprises a cryogenic tank having an outer wall, a non-conducting liner, and a load bearing insulation layer disposed therebetween. The tank holds a liquid or gaseous cryogenic coolant into which the components of the transformer are immersed. A plurality of passages allow the passage of the limbs of the iron core of the transformer through the tank.

Abstract: A ground fault location system is used in a multi-phase ungrounded or high-impedance grounded power network. A signal generator is coupled to the network at a first location and generates for each network phase an individual non-DC voltage signal between such phase and ground. A ground fault detector is coupled to the network at a second location and has a summing device and an annunciator. The summing device is coupled to all of the phases of the network at such second location, sums any current passing therethrough, and produces a sum signal. The annunciator receives the sum signal and provides an indication when such signal is non-zero. Each phase of the network at the second location has a distribution current passing therethrough, the sum thereof normally being substantially zero and resulting in a substantially zero sum signal and the lack of an indication from the annunciator based on such distribution currents.

Abstract: A ground fault location system is used in a multi-phase ungrounded or high-impedance grounded power network. A signal generator is coupled to the network at a first location and generates for each network phase an individual non-DC voltage signal between such phase and ground. A ground fault detector is coupled to the network at a second location and has a summing device and an annunciator. The summing device is coupled to all of the phases of the network at such second location, sums any current passing therethrough, and produces a sum signal. The annunciator receives the sum signal and provides an indication when such signal is non-zero. Each phase of the network at the second location has a distribution current passing therethrough, the sum thereof normally being substantially zero and resulting in a substantially zero sum signal and the lack of an indication from the annunciator based on such distribution currents.