Abstract:
A circuit breaker system  10  (FIG.  1 ) using electronic trip units  35  is disclosed. The electronic trip units  35  are coupled to a communications bus  30  whereby the electronic trip units  35  can be reconfigured, controlled, and/or monitored by a central computer  20.  Further, the electronic trip units are coupled to a separate control power supply line  50  and to a zone selective interlock system.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to electric powered trip units, such as circuit breakers and more particularly to a communication and control system that cooperates with the electronic trip units. 
     BACKGROUND OF THE INVENTION 
     In a typical factory-power distribution system, power is generated by a power generation company and supplied to a factory and thereafter distributed around the factory to various equipment such as, for example, motors, welding machinery, computers, heaters, lighting, and the like. 
     Power distribution systems of this type are typically centrally located in switch gear rooms or substations. From there, power is divided up into branches such that each branch supplies power to a portion of the factory and/or specified loads. Frequently, transformers are disposed throughout the factory to step down the supply voltage to that required by specific pieces of equipment or portions of the factory. Therefore, a factory-power distribution system typically has a number of transformers servicing various types of equipment in various areas. Inherent with this, is the high cost of the power-distribution equipment such as transformers, as well as the cost of the equipment to which power is being supplied. Therefore, it is quite common to provide protective devices such as circuit breakers or fuses in at least each branch so that not only may each piece of equipment be protected but any problems associated with one piece of equipment does not ripple to adjacent or interconnected pieces of equipment. Further, providing fuses or circuit breakers in each branch can help minimize down time since specific loads may be energized or de-energized without affecting other loads thereby creating increased efficiencies, lower operating and manufacturing costs and the like. 
     Typically, when circuit breakers are utilized, they are used to detect more than just large overcurrent conditions caused by short circuit faults. In addition, they frequently detect lower level long-time overcurrent conditions and excessive ground currents. The simplest form of circuit breakers are thermally tripped as a result of heating caused by overcurrent conditions and, in this regard, are basically mechanical in nature. These mechanical-type breakers are incorporated into almost all circuit breakers, regardless of whether or not additional advanced circuitry is provided since they are extremely reliable over a long life cycle and provide a default trip-type level of protection. 
     Some types of circuit breakers utilize electronic circuitry to monitor the level of current passing through the branch circuits and to trip the breaker when the current exceeds a pre-defined maximum value. Electronic circuit breakers are adjustable so as to fit a particular load or condition by the end user without designing or specifying different breakers. Breakers of this type typically include a microcontroller coupled to one or more current sensors. The microcontroller continuously monitors the digitized current values using a curve which defines permissible time frames in which both low-level and high-level overcurrent conditions may exist. If an overcurrent condition has maintained for longer than its permissible time frame, the breaker is tripped. 
     Microcontrolled breakers may also include the ability to calculate root mean square (RMS) current values. This is necessary in order to prevent erroneously tripping a circuit breaker when a non-linear load, such as a welding machine, is coupled to the branch that it is protecting. The reason for this is that nonlinear loads tend to produce harmonics in the current waveform. These harmonics tend to distort the current waveform, causing it to exhibit peak values which are augmented at the harmonic frequencies. When the microcontroller, which assumes that the current waveform is a sinusoidal current waveform, detects these peaks it may therefore trip the breaker even though the heating effect of the distorted waveform may not require that the circuit be broken. 
     Further, microcontrollers in some circuit breakers are used to monitor and control or account for other types of faults, such as over or under voltage conditions and phase loss or imbalances. Such microcontrollers operate solenoids which are operatively connected to the trip mechanism of the circuit breaker. Therefore, while the thermal overload (mechanical) portion of the breaker will operate the trip mechanism, the solenoid will operate at the instruction of the microcontroller (or sometimes also at the instruction of external signals) to allow the trip mechanism to trip the associated circuit breaker. 
     Further, as a result of the flexibility and breadth of protection that microcontrollers can provide when used in conjunction with circuit breakers, their use in circuit breakers is becoming more and more prevalent to the point of being standard. However, this presents another problem in that microcontrollers and the associated circuitry require power. Such power may be typically provided in one of three ways or a combination thereof and would utilized either batteries, externally-supplied power, or power provided by potential transformers. Most users provide one power supply having battery back-up, for supplying all of the controllers for the entire substation or switch gear closet. 
     Moreover, the monitoring of power characteristics is being demanded more and more frequently in load control equipment and particularly in Molded Case Circuit Breakers (MCCB) as is frequently found in use in industry. Such power components include, RMS and peak voltage, current and power, either by phase or in total and power factor related components. Utilities and industrial customers are increasingly interested in performing end-use load studies. These studies are typically in the form of collecting interval power data so as to monitor and control energy consumption. While this is often done at a main load center, due to the increased costs and problems associated with time of use power consumption, such monitoring is being done closer to the individual end-use loads (i.e., motors, etc.). In this fashion, industrial customers are given a financial incentive to curtail power consumption when the cost of power is high as well as being able to more carefully and cost-effectively manage their power consumption by knowing where in their plant significant amounts of energy are being used. 
     When power monitoring is to be done, a discrete energy transducer is installed on the equipment or circuit to be monitored. This transducer generates a digital pulse output via a mechanical or solid state relay with the frequency of the pulse output being proportional to the magnitude of the measured quantity. This digital pulse output is either hard wired or communicated via power line-carrier system to a discrete pulse data recording device where it is time stamped. 
     Because of the flexibility and configurability of microprocessor controlled circuit breakers and the large size and complexity of the industrial settings in which they are used, there is a need for a centralized system providing communications to and from the circuit breakers. Also, there is a need for a communication system providing reconfigurability of the circuit breakers from a centralized location. Further, there is a need for monitoring of circuit breakers at a centralized location. Further still, there is a need for a circuit breaker system that can communicate with a central system, the central system providing monitoring, communication and control functions from a central location to the circuit breaker system. 
     SUMMARY OF THE INVENTION 
     One embodiment of the invention relates to an information system. The information system includes a circuit breaker connectable to a load and having a current interrupting portion. The information system also includes a data processing unit and a communications bus configured to be coupled to the data processing unit. The information system further includes an electronic monitoring unit, configured to provide at least one of monitoring, control, and communications functions for the circuit breaker and the electronic monitoring unit in communication with the circuit breaker and with the communications bus. 
     Another embodiment of the present invention relates to a circuit breaker communications, monitoring, and control system. The circuit breaker communications, monitoring, and control system includes a central data processing unit and a communications bus coupled to the central data processing unit. The system also includes an application specific module coupled to the communications bus and a circuit breaker connectable to a load and having a current interrupting portion, and the circuit breaker coupled to the application specific module and communicating electronic signals with the application specific module. 
     Still another embodiment of the invention relates to a circuit breaker system configured for use in a commercial environment. The circuit breaker system includes a circuit breaker connectable to a load and having a current interrupting portion. The system also includes a data processing means and a communications bus configured to be coupled to the data processing means. The system further includes an interfacing means, configured to provide at least one of monitoring, control, and communications functions for the circuit breaker and the electronic monitoring unit in communication with the circuit breaker and with the communications bus. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will become more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts, in which: 
     FIG. 1 is a block diagram of a circuit breaker communication, monitoring, and control system; 
     FIG. 2 is a block diagram of a circuit breaker having an application specific module in communication with an external communications bus; and 
     FIG. 3 is a block diagram of the circuit breaker of FIG. 2 showing the communication lines in more detail. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 1, a block diagram of a preferred embodiment of a circuit breaker communication, monitoring and control system  10  is depicted. System  10  includes a central computer  20  which may be any type of centralized data processing unit including, but not limited to a personal computer, a work station, a computer server, or a dedicated data processing device. Central computer  20  is coupled to a communications bus  30 . Communications bus  30  may be any of a wide array of standard communications bus architectures including, but not limited to Ethernet, RS-485, fiber optic architectures, or other applicable bus architectures. Communications bus  30  may use any of a number of applicable communications protocols including, but not limited to profibus, profibus DP, TCP/IP, or any other applicable communications protocol. 
     Communications bus  30  is coupled to and in communication with a plurality of application specific modules  35  which are interfacing devices between communications bus  30  and a circuit breaker  40 . Circuit breaker  40  is coupled to a load such as motors  45 . In a preferred embodiment, circuit breaker  40  may be a Molded Case Circuit Breaker (MCCB), but alternatively circuit breaker  40  may be other types of circuit breakers. Circuit breaker  40  may be coupled to any of a variety of load types including, but not limited to, motors  45 , welders, computers, heaters, lights, or any other type of electrical equipment. 
     Circuit breaker  40  is configured to interrupt current flow to motor  45  or any applicable load when any of a variety of overload conditions are detected. Circuit breaker  40  may be tripped either by a short circuit condition, or by electronically sensing an overload condition, the overload condition being preprogrammed into the circuit breaker electronics. Trip types may include, but are not limited to, overload trips, short time trips, ground fault trips, and instantaneous trips. 
     Referring now to FIG. 2, circuit breaker  40  is depicted as having a circuit breaker handle  41  for manual tripping or resetting of circuit breaker  40 . Further, circuit breaker  40  has an electronic trip unit  42 , which in a preferred embodiment includes a liquid crystal display (LCD) readout or may include any type of display. Electronic trip unit  42  may be programmed to cause current interruption when any of a variety of overload conditions is sensed by the electronic trip unit. For example, electronic trip unit  42  may be programmed to interrupt current when a specified root means square (RMS) current value is reached. Further, other types of overload conditions may be specified. 
     In a preferred embodiment, electronic trip unit  42  includes an interface  43  for a communications adapter  44 . Communications adapter  44  may be coupled to a personal computer, or other data processing device or further may be coupled to any of a variety of communications buses or communication devices. Communications adapter  44  allows an attached communications or data processing device to download information from electronic trip unit  42  or alternatively allows communication with electronic trip unit  42  to program electronic trip unit  42  for any of a variety of internal settings. Interface  43  between electronic trip unit  42  and communications adapter  44  may be any of a variety of serial output/serial input (SO/SI), serial input/serial output (SI/SO) communications lines  43 , as depicted in FIG.  3 . Further, communications adapter  44  preferably uses a serial interface  52 , such as serial interface RS-232C as depicted in FIG.  3 . Interface  43  and interface  52  are not limited to serial interfaces of the type shown. Interfaces  43  and  52  may be any of a variety of applicable communications interfaces including Ethernet, parallel interfaces, or any other applicable interfaces. 
     Referring again to FIG. 2, electronic trip unit  42  is coupled to application specific module  35  through a communications line  36 . In a preferred embodiment, communications line  36  may be a three meter cable which is a serial communications interface as depicted in FIG.  3 . Serial communications interface  36  may include a plurality of communications lines such as serial input/serial output (SI/SO) line, serial output/serial input (SO/SI) line, serial clock (SCK) line and auxiliary power and signals line  37 . Auxiliary power and signals line  37  is configured to carry power from ASM  35  to electronic trip unit  42 . 
     As depicted in FIG. 3, serial communication interface  36  is coupled to a monitoring, control, and communication processor  38  of ASM  35 . The monitoring, control, and communication processor  38  carries out monitoring, control, and communication functions for ASM  35 . The functions include communicating information to and from electronic trip unit  42 , transmitting and receiving data from electronic trip unit  42 , including information such as, but not limited to, the type of trip encountered, the time of trip, the current values at time of trip, (for example, a trip log). Further, monitoring, control, and communications processor  38  may provide programming information to electronic trip unit  42 , such as resetting trip values for electronic trip unit  42  and further may be used to receive real-time data from electronic trip unit  42 . Monitoring, control, and communication processor  38  is coupled to a communications module  39  of ASM  35  which may be, in a preferred embodiment, a profibus communications IC SPC-3 communications device and required support electronics. 
     ASM  35  is coupled to a communications bus  30 , such as the RS-485 communications bus depicted in FIG.  3 . 
     To provide functioning of electronic trip unit  42  after a trip or current interruption has occurred, electronic trip unit  42  receives external power through a power line  50  that is coupled to ASM  35 . ASM  35  supplies power to electronic trip unit  42  through line  37  depicted in FIG.  3 . Power line  50  may also supply zone select interlock signals to ASM  37 . Power line  50  further powers ASM  35  (FIG.  2 ). In a preferred embodiment, ASM  35  is powered by a 24 volt line  50 . 
     A zone selective interlock signal communicated along line  50  allows breakers that are downstream from a particular breaker to be tripped without tripping upstream breakers. This functionality allows an overload condition to be sensed and interrupted without interruption of the entire system. (For example, in an industrial setting it would not be desirable to shut down an entire factory system because a single load device fails thereby tripping a single circuit breaker.) 
     Circuit breakers of the type commonly associated with circuit breaker  40  are typically low voltage circuit breakers in the range of 600 volts or less, but the communication and control system discussed above may be configured to operate with circuit breakers of any rated voltage. Further, circuit breakers commonly associated with circuit breakers  40  have current ratings from approximately 63 amps up to 1600 amps, however, other rated currents may also be applied. Further, circuit breakers of the type commonly associated with circuit breaker  40  are three phase circuit breakers which may be three pole or two pole circuit breakers however single phase circuit breakers may also be used. 
     Those who have skill in the art will recognize that the present invention is applicable with many different hardware configurations, software architectures, communications protocols, and organizations or processes. 
     While the detailed drawings, specific examples, and particular formulations given describe preferred embodiments, they serve the purpose of illustration only. The materials and configurations shown and described may differ depending on the chosen performance characteristics and physical characteristics of the communication network. For example, the type of communication network or communication protocols used may differ. The systems shown and described are not limited to the precise details and conditions disclosed. Furthermore, other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the preferred embodiments without departing from the spirit of the invention as expressed in the appended claims.