Electrical fault detection system
First Claim
1. A microcontroller-based system for detecting ground-fault and grounded-neutral conditions in an electrical power distribution system having line and neutral conductors, comprisinga sensor producing an output signal responsive to current flow in both the line and neutral conductors of the electrical power distribution system,a circuit interrupter for interrupting current flow in said power distribution system in response to a trip signal,a microcontroller receiving said sensor output signal and initiating the generation of a trip signal upon detection of a ground-fault or a grounded-neutral condition in said power distribution system, said microcontroller being programmed touse said sensor output signal to detect ground-fault conditions during spaced time intervals, anduse said sensor output signal to detect grounded-neutral conditions during intervening time intervals between said spaced interval.
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Accused Products
Abstract
A microcontroller-based system to detect ground-fault and grounded-neutral conditions in a monitored circuit of an electrical distribution system having line and neutral conductors. The system includes a single sensor producing an output signal responsive to current flow in both the line and neutral conductors of the monitored circuit, and a microcontroller receiving the sensor output signal and initiating the generation of a circuit status signal indicating one of a normal operating condition, a ground-fault condition or a grounded-neutral condition in the monitored circuit. The microcontroller is programmed to continuously test for ground-fault conditions by evaluating the sensor output signal and, at selected intervals, test for grounded-neutral conditions by evaluating the sensor'"'"'s output signal response to a microcontroller initiated ping in the sensor circuit.
21 Citations
26 Claims
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1. A microcontroller-based system for detecting ground-fault and grounded-neutral conditions in an electrical power distribution system having line and neutral conductors, comprising
a sensor producing an output signal responsive to current flow in both the line and neutral conductors of the electrical power distribution system, a circuit interrupter for interrupting current flow in said power distribution system in response to a trip signal, a microcontroller receiving said sensor output signal and initiating the generation of a trip signal upon detection of a ground-fault or a grounded-neutral condition in said power distribution system, said microcontroller being programmed to use said sensor output signal to detect ground-fault conditions during spaced time intervals, and use said sensor output signal to detect grounded-neutral conditions during intervening time intervals between said spaced interval.
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4. A microcontroller-based system for detecting ground-fault and grounded-neutral conditions in an electrical power distribution system having line and neutral conductors, comprising
a sensor producing an output signal responsive to current flow in both the line and neutral conductors of the electrical power distribution system, a circuit interrupter for interrupting current flow in said power distribution system in response to a trip signal. a microcontroller receiving said sensor output signal and initiating the generation of a trip signal upon detection of a ground-fault or a grounded-neutral condition in said power distribution system, said microcontroller being programmed to use said sensor output signal to detect ground fault conditions during spaced time intervals, use said sensor output signal to detect grounded-neutral conditions during intervening time intervals between said spaced interval by using said sensor output signal to estimate the impedance of the neutral-to-ground connection in said power distribution system, and initiating a ping signal in each of said intervening intervals to produce a damped oscillation in said sensor output signal.
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15. A microcontroller-based system for detecting ground-fault and grounded-neutral conditions in an electrical power distribution system having line and neutral conductors, comprising
a sensor, containing a single current transformer producing an output signal responsive to current flow in both the line and neutral conductors of the electrical power distribution system, a microcontroller receiving said sensor output signal and initiating the generation of a trip signal upon detection of said ground-fault or said grounded-neutral condition in said power distribution system, said microcontroller being programmed to use said sensor output signal to detect ground-fault conditions during spaced time intervals, and use said sensor output signal to detect grounded-neutral conditions during intervening time intervals between said spaced time intervals, and a circuit interrupter for interrupting current flow in said power distribution system in response to said trip signal.
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16. A method of detecting ground-fault and grounded-neutral conditions in an electrical power distribution system having both line and neutral conductors, comprising
producing a signal responsive to current flow in both the line and neutral conductors of the electrical power distribution system, supplying said signal to a microcontroller that is programmed to use said signal to detect ground-fault conditions during spaced time intervals, use said signal to detect grounded-neutral conditions during intervening time intervals between said spaced intervals, initiate the generation of a trip signal upon detection of a ground-fault or a grounded-neutral condition, and interrupting current flow in said power distribution system in response to said trip signal.
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19. A method of detecting ground-fault and grounded-neutral conditions in an electrical power distribution system having both line and neutral conductors. comprising
producing a signal responsive to current flow in both the line and neutral conductors of the electrical power distribution system. supplying said signal to a microcontroller that is programmed to use said signal to detect ground-fault conditions during spaced time intervals by comparing the magnitude of said signal with a predetermined threshold value, use said signal to detect grounded-neutral conditions during intervening time intervals between said spaced intervals by estimating the resistance of the neutral-to-ground connection in said power distribution system, initiate a ping signal in each of said intervening time intervals to produce a damped oscillation in said signal, and compares said damped oscillation with a reference value to determine whether a grounded-neutral condition has occurred, initiate the generation of a trip signal upon detection of a ground-fault or a grounded-neutral condition, and interrupting current flow in said power distribution system in response to said trip signal.
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22. A method of detecting ground-fault and grounded-neutral conditions in an electrical power distribution system having both line and neutral conductors and a sensor circuit producing a signal responsive to current flow in both the line and neutral conductors of the electrical power distribution system, comprising
using a real-time clock to produce spaced time intervals, sampling said signal at said spaced time intervals, using the signal sample from each spaced time interval to detect a ground-fault condition, and setting a ground-fault indicator in response to the detection of a ground-fault condition, using said signal sample to detect a neutral-to-ground fault condition, and setting a neutral-to-ground fault indicator in response to the detection of a neutral-to-ground fault condition, initiating the generation of a trip signal in response to the setting of a ground-fault or a neutral-to-ground indicator, and interrupting current flow in said power distribution system in response to said trip signal.
Specification