Abb Power Td & Company

Thomas L Baldwin

Damir Novosel

Harald Reiss

Dietrich Bonmann

Paul Sz&aacute;sz

Varagur R Ramanan

Ali F Imece

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.

Cryostat for use with a superconducting transformer

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. When the second location is on a path between the first location and a ground fault, the individual voltage signal on at least one of the phases generates a fault current thereon through such path and results in a non-zero sum signal and an indication from the annunciator. When the second location is not on such path, none of the individual voltage signals generates a fault current on any phase through such path, resulting in a substantially zero sum signal and the lack of an indication from the annunciator.

Ground fault location system and ground fault detector therefor

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Tallahassee, FL, United States of America

Thomas L Baldwin