Modulating ground fault detector and interrupter

Claim 2

In a protective device for detecting currents to ground in power distribution systems having a plurality of conductors carrying current between a source and a load, sensing means adapted for monitoring the flow of current in the conductors and producing a fault signal whenever the total current flowing toward the load is not equal to the current flowing back to the source through the conductors, modulation means connected for receiving the fault signal from said sensing means and modulating a carrier signal with said fault signal, and demodulation means for demodulating the modulated carrier signal to recover the fault signal.

Claim 3

A protective device as in claim 1 together with amplification means connected intermediate the modulation and demodulation means for amplifying the modulated signal.

Claim 4

A protective device as in claim 1 together with current interrupting means connected for interrupTing the flow of current in the distribution system conductors in response to the fault signal from said demodulation means.

Claim 5

A protective device as in claim 3 wherein said current interrupting means includes contacts connected in series with said conductors, an operating coil for controlling said contacts, and switching means responsive to the fault signal from said demodulator means for controlling the flow of current to said operating coil.

Claim 6

A protective device as in claim 1 wherein said sensing means includes a differential transformer.

Claim 7

In a ground fault current interrupter for interrupting the flow of current in power distribution system having a plurality of conductors carrying current between a load and a source, a differential transformer having a plurality of primary windings connected in the conductors and a secondary winding in which a fault signal is produced whenever the current flowing through the primary windings toward the load is not equal to the current flowing back toward the source through said windings, means for generating a carrier signal, modulation means connected for receiving the fault and carrier signals and adapted for impressing the information carried by the fault signal onto the carrier signal, amplification means or amplifying the signal from said modulation means, demodulation means for removing the fault information from the amplified signal, and current interrupting means controlled by the fault information from said demodulation means for interrupting the flow of current in the distribution system conductors in response to the fault signal.

Claim 8

In a ground fault current interrupter for interrupting the flow of current in power distribution system having a plurality of conductors carrying current between a load and a source, a differential transformer having a plurality of primary windings connected in the conductors and a secondary winding in which a fault signal is produced whenever the current flowing through the primary windings toward the load is not equal to the current flowing back toward the source through said windings, means for generating a carrier signal, modulation means connected for receiving the fault and carrier signals and adapted for impressing the information carried by the fault signal onto the carrier signal, amplification means or amplifying the signal from said modulation means, demodulation means for removing the fault information from the amplified signal, and current interrupting means controlled by the fault information from said demodulation means for interrupting the flow of current in the distribution system conductors in response to the fault signal.

Claim 9

A ground fault current interrupter as in claim 6 wherein said current interrupting means includes at least one normally closed contact connected in at least one of said conductors and an operating coil for opening said contact.

Claim 10

A ground fault current interrupter as in claim 7 together with switching means connected intermediate said demodulation means and said operating coil.

Claim 11

A ground fault current interrupter as in claim 6 wherein said modulation means includes an amplitude modulator.

Claim 12

A ground fault current interrupter as in claim 6 wherein said modulation means includes a frequency modulator.

Claim 13

A ground fault current interrupter as in claim 6 wherein said modulation means includes a phase modulator.

Claim 14

In a ground fault current interrupter for interrupting the flow of current in power distribution system having a plurality of conductors carrying current between a load and a source, sensing means adapted for monitoring the flow of current in the conductors and producing a fault signal whenever the total current flowing toward the load is not equal to the current flowing back to the source through the conductors, pulse generating means, pulse sampling means connected to the sensing and pulse generating means for sampling the fault signal at a rate determined by the rate of pulses from said generating means, switching means connected to said sampling means and controlled by the sampled fault signal, and current interrupting means controlled by said switching means for interrupting the flow of current in the distribution system conductors upon the occurrence of a ground fault.

Claim 15

In a ground fault current interrupter for interrupting the flow of current in power distribution system having a plurality of conductors carrying current between a load and a source, sensing means adapted for monitoring the flow of current in the conductors and producing a fault signal whenever the total current flowing toward the load is not equal to the current flowing back to the source through the conductors, pulse generating means, pulse sampling means connected to the sensing and pulse generating means for sampling the fault signal at a rate determined by the rate of pulses from said generating means, switching means connected to said sampling means and controlled by the sampled fault signal, and current interrupting means controlled by said switching means for interrupting the flow of current in the distribution system conductors upon the occurrence of a ground fault.

Claim 16

A ground fault current interrupter as in claim 12 wherein said pulse sampling means includes an amplifier which derives its operating power from said pulse generating means in such manner that said amplifier alternates between on and off conditions at a rate determined by said pulse generating means.

Claim 17

In a ground fault current interrupter for interrupting the flow of current in power distribution system having a plurality of conductors carrying current between a load and a source sensing means adapted for monitoring the flow of current in the conductors and producing a fault signal whenever the total current flowing toward the load is not equal to the current flowing back to the source through the conductors, amplifier means having an input and an output, modulation meaNs connected intermediate said sensing means and said amplifier means and adapted for applying the fault signal intermittently to the input of said amplifier means, and demodulation means connected to the output of said amplifier means for intermittently passing the signal from said output.

Claim 18

In a ground fault current interrupter for interrupting the flow of current in power distribution system having a plurality of conductors carrying current between a load and a source sensing means adapted for monitoring the flow of current in the conductors and producing a fault signal whenever the total current flowing toward the load is not equal to the current flowing back to the source through the conductors, amplifier means having an input and an output, modulation meaNs connected intermediate said sensing means and said amplifier means and adapted for applying the fault signal intermittently to the input of said amplifier means, and demodulation means connected to the output of said amplifier means for intermittently passing the signal from said output.

Claim 19

A ground fault current interrupter as in claim 14 wherein said amplifier means comprises an operational amplifier having inverting and noninverting inputs.

Claim 20

In a protective device for detecting currents to ground in power distribution systems having a plurality of conductors carrying current between a source and a load, a differential transformer having a plurality of primary windings connected in the conductors and a secondary winding in which a fault signal is produced whenever the current flowing through the primary windings toward the load is not equal to the current flowing back toward the source through said windings, means for generating a carrier signal, magnetic modulation means including a reactor core coupled to the secondary winding of said differential transformer and adapted for modulating a carrier signal in accordance with the fault signal, and demodulation means for demodulating the modulated carrier signal to recover the fault signal.

Claim 21

In a protective device for detecting currents to ground in power distribution systems having a plurality of conductors carrying current between a source and a load, a differential transformer having a plurality of primary windings connected in the conductors and a secondary winding in which a fault signal is produced whenever the current flowing through the primary windings toward the load is not equal to the current flowing back toward the source through said windings, means for generating a carrier signal, magnetic modulation means including a reactor core coupled to the secondary winding of said differential transformer and adapted for modulating a carrier signal in accordance with the fault signal, and demodulation means for demodulating the modulated carrier signal to recover the fault signal.

Claim 22

A protective device as in claim 16 together with means for generating a carrier signal and means for delivering the carrier and fault signals to the reactor core in such manner that said carrier signal is amplitude modulated by said faults signal in said reactor core.

Claim 23

A protective device as in claim 16 wherein said reactor core is utilized in a frequency determining element in an oscillator to produce a frequency modulated signal varying in accordance with said fault signal.

Claim 24

A protective device as in claim 16 wherein said reactor core constitutes an element in a phase shifting network for phase modulating the carrier signal in accordance with said fault signal.

Claim 25

In a method for detecting ground fault currents in a power distribution system of the type having a plurality of conductors between a source and a load, the steps of monitoring the flow of current in said conductors and producing a fault signal whenever the total currents flowing to and from the load in the conductors are not equal, modulating said fault signal onto a carrier signal, amplifying the modulated signal, and demodulating the amplified signal to recover the fault information carried thereby.

Claim 26

In a method for detecting ground fault currents in a power distribution system of the type having a plurality of conductors between a source and a load, the steps of monitoring the flow of current in said conductors and producing a fault signal whenever the total currents flowing to and from the load in the conductors are not equal, modulating said fault signal onto a carrier signal, amplifying the modulated signal, and demodulating the amplified signal to recover the fault information carried thereby.

Claim 27

A method as in claim 20 together with the additional steps of connecting current interrupting contacts in said conductors, said contacts adapted to be opened by an operating coil, and energizing said operating coil in response to the fault information from said carrier signal.

Claim 28

In a method for detecting ground fault currents in a power distribution system of the type having a plurality of conductors between a source and a load, the steps of monitoring the flow of current in said conductors and producing a fault signal whenever the total currents flowing to and from the load in the conductors are not equal, sampling said fault signal at a predetermined rate, and using the sampled fault signal for triggering a switching device to interrupt the flow of current in the distribution system conductors in response to a ground fault current.

Claim 29

In a method for detecting ground fault currents in a power distribution system of the type having a plurality of conductors between a source and a load, the steps of monitoring the flow of current in said conductors and producing a fault signal whenever the total currents flowing to and from the load in the conductors are not equal, sampling said fault signal at a predetermined rate, and using the sampled fault signal for triggering a switching device to interrupt the flow of current in the distribution system conductors in response to a ground fault current.

Claim 30

A method as in claim 22 wherein said fault signal is sampled at a predetermined rate by means of a contact modulator.