Littelfuse, Inc.

Littlefuse, Inc.

Michael Vangool

Geoffrey J Baker

Nehad El-Sherif El-Kharbawe

George J Fenty

A ground check monitoring device coupled to a trailing cable includes a voltage source and a switch. The trailing cable includes a first conductor, a second conductor, and a ground conductor. A resistive termination device is coupled between the first conductor and the ground conductor. A controller of the ground check monitoring device can toggle the switch between a first node of the first conductor and a second node of the second conductor. By measuring voltages at the first and second nodes, the ground check monitoring device can determine if the resistive termination device is shorted. Further, the controller can calculate resistance values of the first and second conductors and calculate a resistance value of the ground conductor. The calculated resistance values can be compared to expected values and the controller can signal a ground fault condition as appropriate based on the comparisons.

Two-wire resistance terminated ground check

A device for monitoring a neutral grounding resistor (NGR), including first and second NGRs electrically connected in parallel, a rectifier circuit electrically connected in series with the second NGR and a voltage source and a logic resistor electrically connected in series with the second NGR. A logic circuit measures current passing through the logic resistor and determines the resistance of the first NGR based on the measured current and the resistance of the second NGR. As such, a failed-open or failed-short condition of the first NGR may be identified based at least in part on the determined resistance of the first NGR.

Neutral grounding resistor monitor

A method for processing output from a current transformer comprising deriving signal data from the output; converting the signal data from analog to digital format; removing a carrier signal from the signal data; squaring the signal data; and performing a recursive RMS algorithm on the signal data.

AC/DC current transformer

A single-coil, toroid-type current transformer circuit for detecting both AC and DC current. The current transformer circuit may include a current transformer and an oscillator electrically connected to the current transformer. The current transformer circuit may further include an open and short CT detection circuit electrically connected to the oscillator for facilitating determination of the connection and stability state of the current transformer. A processor may be electrically connected to an output of the open and short CT detection circuit for performing a series of operations on signal data generated by the open and short CT detection circuit and manipulating the operation of an electrical power system accordingly.

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Saskatoon, Canada

Michael Vangool