Westinghouse Electric Corporation

Herbert E Pietsch

Tapan K Gupta

Ronald T Harrold

Emil M Fort

Charles L Neumeyer

A method of making a ZnO powder composition, which can exhibit non-linear V-I characteristics, comprises the steps of: (1) mixing about 75 mole % to about 98 mole % of small, finely divided, solid ZnO and about 2 mole % to about 25 mole % of at least one small, finely divided, solid additive oxide effective to produce nonlinear characteristics, with an aqueous binder solution comprising an organic, water soluble fugitive binder, to provide a slurry; (2) simultaneously drying, mixing and agglomerating the slurried solids into a mass of larger substantially spherical particles containing the finely divided solids and binder; (3) pressing a mass of the agglomerated particles, to provide a cohesive pressed green body; and then (4) heating the pressed body, first at a temperature rate increase effective to slowly decompose and remove the fugitive binder from the body and then heating at a temperature of between 1,050.degree. C. to about 1,400.degree. C. for a time effective to sinter together the particles of the body, forming ZnO grains; (5) crushing the sintered body to provide finely divided powder particle fragments; (6) passing the particle fragments through a means to measure particle size in a manner effective to provide at least two attached ZnO grain fragments per particle, to provide a non-linear ZnO powder; and optionally, (7) heating the non-linear ZnO particles at a temperature of between 500.degree. C. and 1,050.degree. C. and breaking up any agglomerates, to provide a finely divided powder which will exhibit non-linear V-I characteristics.

Method of producing homogeneous ZnO non-linear powder compositions

An insulated electrical member is made, having in combination, an electrical member covered with insulation and a conducting varnish, where an abrasion resistant stress grading system covers at least part of the conducting varnish, the stress grading comprising: (1) a first base layer of resinous paint containing non-linear SiC having a resistivity value of between 2,000 to 4,000 Meg. Ohm/Square, in contact with the conducting varnish, (2) a second overlapping layer of resinous paint containing non-linear SiC having a resistivity value of between 4,000 to 6,000 Meg. Ohm/Square and containing at least one fibrous support, covering the first base layer and (3) an overcoat of an arc and track resistant resinous insulating varnish; where, at the point of overlap of the SiC layers, the thickness ratio of the base SiC layer:overlapping SiC layer is from 1:1 to 1:15.

Multilayered high voltage grading system for electrical conductors

A method is provided for detecting the presence of arcing faults in the stator windings of large dynamoelectric machines, such as turbine generators. Arcing faults, such as broken strands in a winding conductor with continued arcing, give rise to high frequency currents which flow in the neutral lead of the generator winding. The presence of the arcing fault can thus be detected by observing the high frequency neutral currents and monitoring them for the presence of the characteristic frequency distribution resulting from the resonance characteristics of the current path.

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Monroeville, PA, United States of America

Herbert E Pietsch