Southern California Edison Company

Southern California Edison

Juan P Lopetrone

Oliver Valdes

Manuel R Cabison

Kevin C Sullivan

James Clopton, Jr

Mauro G Dresti

James J Regan

Tom Baker

Isidor Kerszenbaum

An analyzer for performing high and low voltage tests on an electric induction machine having electric power input terminals. The analyzer comprises: (a) a high voltage testing circuit for performing high voltage tests on the induction machine; (b) a low voltage testing circuit for performing low voltage tests on the induction machine; (c) electrical terminals for electrical connection with the power input terminals of the induction machine; (d) a plurality of switches electrically connecting the high voltage testing circuit and the low voltage testing circuit to the terminals, each switch having one or more control input terminals for receiving control signals for closing and opening the switch; and (e) a controller having a first set of output terminals electrically connected to the control input terminals of the switches, the controller providing control signals to the switches to selectively open one or more of the switches and to selectively close one or more of the switches to: (i) provide electrical conduction paths between the high voltage testing circuit and the induction machine through the closed switches, while electrically isolating the low voltage testing circuit from the high voltage testing circuit through the open switches; and (ii) provide electrical conduction paths between the low voltage testing circuit and the conduction machine through the closed switches, while electrically isolating the high voltage testing circuit from the low voltage testing circuit through the open switches.

Electric motor analyzer

Disclosed is a ground fault detection apparatus for an operating, normally ungrounded supply system, the apparatus having a periodically grounded center tap of a test impedance that is connected across conductors of the system, and detector circuitry including a charge balance circuit having low gain and wide dynamic range that measures the amplified voltage output of a Hall effect current sensor. A preferred implementation of the circuit has a charge transfer variable oscillator. A pair of microprocessor-controlled counters that are responsive to the oscillator precisely measure the average frequency of the oscillator over intervals that are automatically maintained at approximately one second in duration, the microprocessor calculating the fault current as the difference between current measurements taken with and without the center tap grounded. The apparatus has sufficient dynamic range for directly measuring system currents on the order of 100 A, while reliably detecting leakage currents in the milliampere range.

Portable ground fault detector

A current sensing device particularly for rotor ground fault detection in a highly inductive field is able to sense and identify the location of low order fault current when the load current in conductors is on the order of at least 1,000 amperes. Laminated strips of magnetic material are flexible to be located ideally about the conductors to maximize the sensitivity signal and minimize the effect of electromagnetic radiation. The current sensor includes three sets of laminations, the central laminations being for magnetization sensing, the inner laminations being for magnetic filtering, and outer laminations being for magnetic shield. Magnetic separation exists between each lamination set. Electrical insulation is located about the inner and outer sets.

Current sensing

Apparatus for the detection of leakage current in a system includes a power supply and conductors from the supply for supplying power to a load connected to the system. There is an interrupter connected in the system and to a ground point such that a ground leakage current in the system has a closed circuit. Activation of the interrupter about every 12 seconds effectively generates a pulse interrupted ground fault signal. Such signal is detected by a magnetic sensor located relative to a multi-feeder system with high capacitive reactance. The sensor is immune to random electromagnetic and electrostatic conditions in the distribution system. The sensor is synchronized to operate with the interrupter so that sensing is effected at a steady level of a square wave interrupted pulse.

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Palos Verdes, CA, United States of America

Juan P Lopetrone