Kearney-national Inc.

Dipl.-ing. H. Horstmann Gmbh

Kearney

Arthur C Westrom

Billy R Livesay

James Wagner Larsen

George J Cokkinides

W Ralph Crooks

James W Larsen

A P Meliopoulos

A fault distance locator for underground cable circuits for calculating more accurately the location of a cable fault includes a pulse generator unit for injecting a series of chirped pulse streams into the faulted cable shortly after the cable fault has been established. The delay times between the reflected pulse signals and the sending pulse signals are obtained by a correlation process which is specially designed to eliminate the effect of noise caused by arcing voltage and thus provide an accurate calculation of the distance to the cable fault. The accuracy is further enhanced by injecting pre-fault pulse signals periodically into the cable prior to the occurrence of the cable fault in order to obtain a reference pulse signal. This pulse signal provides information concerning the speed of propagation of the cable and thus affects the distance calculation to the fault.

Fault distance locator for underground cable circuits

A system for detecting a high impedance fault in a phase conductor having a potential device connected to the phase conductor, the system including a signal injection device having an input from the potential device which detects a reduction in voltage at the phase conductor and outputs a first signal in response to detecting a reduction in voltage at the phase conductor and a signal receiver which receives the first signal and provides a second signal to an interruption device in response to having received the first signal to cause the interruption device to open the circuit to the phase conductor.

Method and apparatus for detecting and responding to downed conductors

A surge arrester of modular form, including a metal oxide varistor disk having a coaxial shunt gap located within the disk. The metal oxide varistor disk has a hole located essentially through the center of the disk and includes top and bottom electrode plates having centrally located projections which protrude inwardly of the disk into the hole of the disk, thereby forming a shunt gap within the disk. The module may be used unhoused in under-oil applications or as a component part of a housed arrester. For under-oil applications, the electrode plates are solder sealed to the disk providing a seal preventing oil or moisture from entering the hole in the shunt gap. As an alternate embodiment the surge arrester module may include a series of two or more of such disks stacked between the top and bottom electrode plates.

Surge arrester with shunt gap

In a current limiting fuse, the combination of a plurality of metallic fuse strips and a packing of silica enveloping said strips, said strips being made of cadmium alloyed with a grain size stabilizing minor amount of a metal selected from the group consisting of zinc and silver.

Element for a current limiting fuse

For interrupting all values of electric current in a high voltage circuit which cause operation of a fuse within one hour, a plurality of parallel connected helically configured fusible elements formed of cadmium are embedded within quartz sand in granular form disposed within a housing structure which includes a tubular member of insulating material to the ends of which terminal caps are secured and connected to the ends of the fusible elements respectively so that currents of a high order of magnitude are interrupted in a fraction of a half cycle in a current limiting fashion and so that currents of a low order of magnitude and which are slightly in excess of normal rated load current of the fuse cause the temperature of the fusible elements to rise to the melting point within a longer predetermined period of time and then to establish a gap sufficient to withstand the recovery voltage. For substantially preventing degradation processes in the cadmium fusible elements, a non-porous metallic coating of substantially uniform thickness between 0.5 and 10 microns is arranged to cover each fusible element and wherein there is substantially no inter-metallic diffusion through the interface between the cadmium fusible elements and their metallic coatings at temperatures below the melting temperature of cadmium.

Metallic coating for a cadmium fuse

A surge arrester of compact construction includes a housing formed preferably of elastomeric material through which a pair of spaced terminals protrude and between which a stack of metal oxide varistor discs is disposed and connected in series therewith. Disposed below the lower one of the discs and in contact therewith is a conductive base plate and an electrode is spaced somewhat from the lower surface of the base plate to form a gap and is provided with shunt means connecting the electrode with the upper surface of the lower disc so that an overvoltage surge condition and the resulting arc across the gap establishes a shunt circuit around the lower disc. Thus the lowermost disc is effectively shunted during surge conditions thereby enhancing the protective response of the device while the lowermost disc is in the circuit during stabilized conditions and effectively increases the overall resistance of the arrester and by this means limits the magnitude of current and prevents undesirable overheating and the attendant run away tendency of the arrester. Since the elastomeric housing is in direct heat transferring contact with the stack of varistors, heat transfer to atmosphere is greatly facilitated.

Surge arrester having coaxial shunt gap

A current limiting fuse and an oil expulsion or weak link type fuse are connected in series with each other and with a transformer primary winding and a grounded element having a part disposed adjacent one end of the expulsion fuse is arranged so that an arc drawn upon operation of the expulsion fuse is directed to the grounded element in such manner as to cause the current limiting fuse to operate and interrupt the flow of current through the primary winding. The system is applicable to single phase or multiple phase arrangements.

Transformer protective system

An electric terminal bushing having a hollow tubular contact engageable with the contact pin of an electric elbow type connector is arranged so as substantially to reduce the arcing time during a switch closing operation and includes means for slidably mounting the hollow tubular contact within the bushing and magnetic means connected in series with the contact for imparting sliding closing movement thereto in response to the striking of an electric arc between the contact pin and the tubular hollow contact.

Growing community of inventors

Stone Mountain, GA, United States of America

Arthur C Westrom