Multifunctional residential circuit breaker

• US 8,023,235 B2
• Filed: 03/17/2009
• Issued: 09/20/2011
• Est. Priority Date: 10/31/2006
• Status: Active Grant

• Current Assignee: Siemens Industry Incorporated (Siemens AG)
• Original Assignee: Siemens Industry Incorporated (Siemens AG)
• Inventors: Bilac, Mario, Restrepo, Carlos, Nayak, Amit, Kinsel, Hugh T.
• Primary Examiner(s): Salce; Patrick
• Application Number:
  US12/405,340
• Publication Number:
  US 20090198459A1
• Time in Patent Office: 917 Days
• Field of Search: 361/42, 361/93.1, 361/94, 361/45, 324/500
• US Class Current: 361/42
• CPC Class Codes: G01R 31/3277 of low voltage devices, e.g. domestic or industrial devices, such as motor protections, relays, rotation switches
• CPC Class Codes: H02H 1/0015 Using arc detectors
• CPC Class Codes: H02H 1/0092 concerning the data processing means, e.g. expert systems, neural networks
• CPC Class Codes: H02H 3/33 using summation current transformers H02H3/347 takes precedence

Abstract

An electrical fault detection device for use in a branch of a power circuit that utilizes signals from an AC line current sensor coupled to an electrical distribution line having a primary and neutral lines, a line high-frequency sensor coupled to the electrical distribution line, a differential current sensor coupled to the primary and neutral lines, and a ground fault current sensor coupled to the primary and neutral lines. A signal conditioner receives the signals outputted by AC current line current sensor, the line high frequency sensor, the differential current sensor and the ground fault current sensor and generates a signal indicative of the load current associated with a branch of the power circuit. Output of the signal conditioner is sampled and processed by a processing resource. The processing resource has stored therein data representing a plurality of time-versus-current curves that define a plurality of regions in which tripping may or may not occur. One region has time data and current data that define a time-duration for a particular current magnitude for which no tripping will occur. Another region has time data and current data that define a time-duration of a particular current magnitude for which tripping will occur. Processing resource processes sampled signal to determine the region to which the processed time data and current data correspond, and generates a signal to initiate tripping if the sampled signal yields a time duration for a particular current magnitude that corresponds to a region for which tripping must occur.

Claims

1. An electrical fault detection device for use in a branch of a power circuit, comprising:

an AC line current sensor for monitoring the AC current in an electrical distribution line comprising a primary line and neutral line and carrying an AC power signal the AC line current sensor generating a representative signal proportional to the load current delivered to at least one branch of a power circuit;

a line high-frequency sensor coupled to the electrical distribution line for detecting and outputting a broadband high-frequency component of the AC power signal;

a differential current sensor coupled to the primary and neutral lines of the electrical distribution line for monitoring the net current between the primary line and neutral line, comparing the net current with the AC load current signal and generating a signal that indicates whether the net line-to-neutral current is inconsistent with a load current by a predetermined acceptable amount;

a ground fault current sensor for detecting a current imbalance between the primary and neutral lines of the electrical distribution line;

a signal conditioner in electrical signal communication with the AC current line current sensor, the line high frequency sensor, the differential current sensor and the ground fault current sensor and adapted to generate a signal indicative of the load current associated with a branch of the power circuit;

a sampling circuit for sampling the signal outputted by the signal conditioner and generating a sampled signal; and

a processing resource for processing the sampled signal, the processing resource having stored therein data representing a plurality of time-versus-current curves that define a plurality of regions in which tripping may or may not occur, wherein at least one region has time data and current data that define a time duration for a particular current magnitude for which no tripping will occur, and wherein at least one other region has time data and current data that define a time duration for a particular current magnitude for which tripping will occur, the processing resource processing the sampled signal to (i) provide processed time data and current data, (ii) determine the region to which the processed time data and current data correspond, and (iii) generating a signal to initiate tripping if the sampled signal yields time data and current data that corresponds to a region for which tripping must occur.

2. The electrical fault detection device according to claim 1 wherein the AC line current sensor comprises a transformer coupled to the primary and neutral lines.

3. The electrical fault detection device according to claim 1 wherein the AC line current sensor comprises a metallic strap of known impedance in series with the load that provides an output signal indicative of the current travelling through the distribution line.

4. The electrical fault detection device according to claim 1 wherein the AC line current sensor comprises a temperature sensor.

5. The electrical fault detection device according to claim 1 wherein the line high-frequency sensor comprises a high-frequency coupling transformer for collecting high-frequency signals from the distribution line.

6. The electrical fault detection device according to claim 1 wherein the line high-frequency sensor comprises a toroidal-shaped ferrite sensor for collecting high-frequency signals from the distribution line.

7. The electrical fault detection device according to claim 1 wherein the line high-frequency sensor comprises a high pass filter device that allows the passage of high-frequency signals and rejecting low-frequency signals.

8. The electrical fault detection device according to claim 1 wherein the differential current sensor comprises comparator circuitry for comparing the net current with the AC load current signal and outputting the signal that indicates whether the net line-to-neutral current is inconsistent with a load current by a predetermined acceptable amount.

9. The electrical fault detection device according to claim 1 wherein the ground fault current sensor comprises a toroid in electrical signal communication with the primary and neutral lines such that a grounded neutral fault forms a magnetic path that passes through the grounded neutral toroid to allow the toroid to induce an oscillatory wave on both the primary and neutral lines, wherein induced current flows only in the neutral line due to the grounded neutral fault path.

10. The electrical fault detection device according to claim 1 wherein the signal conditioner comprises an AC current conditioning system which comprises a transformer that is coupled to the signals provided by the AC current line current sensor, the line high frequency sensor, the differential current sensor and the ground fault current sensor and which provides a representative signal that is proportional to the low frequency load current.

11. The electrical fault detection device according to claim 1 wherein the sampling circuit comprises an analog-to-digital converter that is in electric signal communication with the signals outputted by the signal conditioner.

12. The electrical fault detection device according to claim 1 wherein the processing resource comprises a microprocessor.

13. A method for electrical fault detection comprising:

monitoring the AC current in an electrical distribution line comprising a primary line and neutral line and carrying an AC power signal;

generating a representative signal proportional to the load current delivered to at least one branch of a power circuit;

detecting and outputting a broadband high-frequency component of the AC power signal;

monitoring the net current between said primary line and neutral line;

comparing said net current with the AC load current signal and generating a signal that indicates whether the net line-to-neutral current is inconsistent with a load current by a predetermined acceptable amount;

detecting a current imbalance between the primary and neutral lines of the electrical distribution line;

generating a signal indicative of the load current associated with a branch of the power circuit, wherein said signal indicative of the load current is based on (i) said representative signal that is proportional to the load current delivered to at least one branch of a power circuit, (ii) said detected broadband high-frequency component of the AC power signal, (iii) said signal that indicates whether the net line-to-neutral current is inconsistent with a load current by a predetermined acceptable amount, and (iv) said detected current imbalance between the primary and neutral lines of the electrical distribution line;

sampling said signal indicative of the load current associated with a branch of the power circuit;

providing a processing resource having stored therein data representing a plurality of time-versus-current curves that define a plurality of regions in which tripping may or may not occur, wherein at least one region has time data and current data that define a time duration for a particular current magnitude for which no tripping will occur, and wherein at least one other region has time data and current data that define a time duration for a particular current magnitude for which tripping will occur; and

processing the sampled signal with the processing resource to (i) provide processed time data and current data, (ii) determine the region to which the processed time data and current data correspond, and (iii) generating a signal to initiate tripping if the sampled signal yields time data and current data that corresponds to a region for which tripping must occur.