Electricity: electrical systems and devices – Safety and protection of systems and devices – Feeder protection in distribution networks
Reexamination Certificate
1998-11-12
2001-02-27
Sherry, Michael J. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Feeder protection in distribution networks
C361S066000, C361S068000, C361S096000, C361S097000
Reexamination Certificate
active
06195243
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention pertains in general to circuit breakers and, more particularly, to a load center monitor in a network of electronically controlled circuit breakers for providing monitoring, analysis and control of circuit breaker function.
BACKGROUND OF THE INVENTION
In a typical AC power distribution system in a residential or small business building, an array of electromechanical circuit breakers protects various branch circuits of the electrical wiring. Such circuit breakers utilize a thermally operated switch which, upon reaching a predetermined temperature due to excessive current passing therethrough, will “trip” and open the circuit connected to the switch. Several problems, with such circuit breakers include the slow response of the thermal tripping mechanism and the inability to closely match or adapt the response characteristic or profile to a particular load circuit.
Improved circuit breakers are disclosed in U.S. Pat. No. 4,949,214, entitled “TRIP DELAY OVERRIDE FOR ELECTRICAL CIRCUIT BREAKERS” issued to George A. Spencer on August 14, 1990, an assignee of the present U.S. Patent Application, and in pending U.S. Pat. No. 5,875,087 entitled “CIRCUIT BREAKERS WITH INTEGRATED CONTROL FEATURES”, issued to the inventors of the present application on Feb. 23, 1999 and assigned to the assignee of the present application, which documents are incorporated herein by reference. Among the features integrated into these improved circuit breakers are the ability to trip when either of the following three parameters exceeds allowable limits: load current, arcing response and ground fault leakage current. The improved circuit breakers disclosed therein include an array of trip profiles tailored to the current draw characteristics of the various kinds of devices which may be connected to the AC power line branch circuit protected by the circuit breaker. These trip profiles, which are dynamically changeable, determine the current versus time configuration of the particular circuit breaker. The trip profiles of these improved circuit breakers are stored in the circuit breaker memory for use during operating routines of the circuit breaker microprocessor while monitoring parameters associated with the circuit breaker load current. The monitored parameters, such as voltage, current and temperature are analyzed and compared with the stored trip profile values to provide very fast trip action as compared with the relatively slow thermally-based trip characteristic of standard circuit breakers. Moreover, rather than being an approximation to a standardized load current vs. time characteristic, the trip profiles of the aforementioned improved circuit breakers can be closely matched to particular loads and enable much more accurate determination of true fault conditions that require removal of electrical power from the load circuit experiencing the fault. Thus, such improved circuit breakers overcome the principal disadvantages of the conventional thermally operated circuit breakers, including, for example, slow response time, inability of responding to differing in-rush current characteristics, inability of opening a circuit upon the occurrence of arcing (a potentially serious fire hazard), inadequate response to electrical stalling of motors connected to a protected line, etc.
Although the circuit breakers with trip delay override and the electronically controlled circuit breakers with integrated control features referenced above and hereinbelow as digitally enhanced circuit breakers, offer superior trip performance under a variety of load fault conditions, several significant new features and capabilities, if provided in conjunction with such advanced circuit breakers, would overcome the following shortcomings. Neither of the aforementioned advanced circuit breakers has the capability of storing substantial quantities of system data, for example in a high capacity, non-volatile memory, when a total power failure occurs. Moreover, the performance of an individual digitally enhanced circuit breaker (DE breaker) is monitored only by the internally executed program within the individual DE breaker. Thus, the data gathering and reporting capabilities of the individual digitally enhanced circuit breakers are not fully exploited by presently available devices. Further, no provision is made in such DE breakers to analyze power line circuit conditions that are common to all DE breakers in the power distribution system in order to obtain an evaluation of the conditions of the system such as may exist when arcing occurs somewhere in the power line network or an open or intermittent connection occurs in a line or neutral conductor upstream from the DE Breakers. There is additionally no affordable means available, even with the advanced circuit breakers mentioned hereinabove, for presently monitoring, controlling or reconfiguring circuit breaker elements within an electrical power distribution system in residential environments.
SUMMARY OF THE INVENTION
The present invention disclosed and claimed herein comprises a circuit breaker system that includes a plurality of individual breakers and a central controller. The individual breakers each have a controller for controlling the operation of the associated breaker and a monitor for monitoring the operation of the breaker. A historical memory is also provided for storing monitored information generated over time by the monitor. A breaker communication port is provided for communicating with the historical memory. A communication interface provides communication interface between each of the breakers, and its associated communication port, and a controller communication port on the central controller. The central controller has a central memory for storing historical memory information associated with select ones of the individual breakers and also includes a communication device. The communication device is operable to communicate through the central controller communication port with a select one of the breakers and for accessing the contents of the associated historical memory and downloading data therefrom for storage in the central memory.
In another aspect of the present invention, the operating trip profiles of the individual circuit breakers may be adaptively reconfigured by a central controller coupled through a communication network to each circuit breaker. Power line data sampled and stored by each individual circuit breaker is downloaded to the central controller where it is compared with historical power line data for that circuit breaker accumulated in the memory of the central controller. The resulting comparison may be averaged over a plurality of successive cycles to produce update data for that circuit breaker and then used to select an appropriate operating trip profile or to replace one or more of the data constants comprising the operating trip profile. The alternate profile selection or the new operating profile is uploaded to the individual circuit breaker and stored in its memory. This reconfiguration procedure may be performed sequentially for each circuit breaker in the network and repeated periodically.
In another aspect of the present invention, current or historical power line data on arcing events provided by the circuit breakers can be analyzed and used to determine whether or not arcing sensitivity should be reduced so that nuisance tripping can be avoided for arc events that do not constitute a hazard or which may be encountered during maintenance.
In another aspect of the present invention, current or historical power line data on arcing events provided by the circuit breakers can be analyzed and used to determine whether or not neutral faults or other open or intermittent circuit connections exist in the system requiring communication of an alarm or other control signal.
REFERENCES:
patent: 5038246 (1991-08-01), Durivage, III
patent: 5164875 (1992-11-01), Haun et al.
patent: 5301083 (1994-04-01), Grass et al.
patent: 5341268 (1994-08-01), Ishiguro et al.
patent: 5373411 (1994-12
Blanton LeRoy
Clunn Robert Henry
Spencer George Auther
Howison Gregory M.
Howison, Chauza, Handley & Arnott, L.L.P.
Mosher Stephen S.
Sherry Michael J.
Spencer George Auther
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