Patent Application
20210203150
The present disclosure relates to electrical distribution panels and load centers and, more particularly, to methods and systems for implementing load centers that can detect and suppress arc formation in branch circuit breakers without adversely affecting other devices connected to the load centers.
Arcing refers to an electrical discharge through a normally nonconductive gas, usually air. In a load center, arcing can occur between any exposed conductors of different electrical potentials, such as between adjacent busbars or a busbar and ground, as well as between current-carrying contacts in the branch circuit breakers. When a branch breaker trips and the current-carrying contacts start to separate, an arc can form across the air gap between the two contacts as current continues flowing until the contacts attain sufficient separation.
Arcing can produce extremely hot gasses, vaporized metals/polymers, and other harmful byproducts. These arc byproducts can damage circuit breaker components, causing them to wear out more quickly than usual, and even rendering the breakers no longer operational in some cases. As a result, circuit breakers are required to be constructed from heavier and stronger materials and have bigger casings in order to provide a large enough contact chamber to satisfy industry standards and ratings requirements.
Accordingly, as can be readily appreciated, improvements are needed in the field of electrical distribution panels and load centers, particularly with respect to arcing in the branch breakers of such load centers.
The present disclosure provides methods and systems for implementing electrical distribution panels and load centers that can detect and suppress arc formation in branch breakers. The methods and systems provide a load center that is equipped to monitor a branch breaker for indications of an arc being formed. The load center may include a main breaker that can immediately cut current flow upon receiving an indication of an arc forming in a branch breaker. The indication may be provided by a sensor mounted on or near the branch breaker that sends a trigger signal to the main breaker when arc formation is detected within the branch breaker. The main breaker then determines whether the trigger signal satisfies a certain condition or conditions indicative of arc formation. If so, the main breaker cuts current flow to suppress the arc, then waits a short period of time while the branch breaker clears before restoring current flow. The wait period is preferably short enough such that devices receiving power from the load center are not adversely affected by the interruption in current flow. To improve current cutoff and restoration response times, the main breaker employs a solid-state trip switch capable of extremely fast switching times.
In general, in one aspect, embodiments of the present disclosure relate to a load center. The load center comprises, among other things, a plurality of branch breakers, and at least one sensor coupled to the plurality of branch breakers. The at least one sensor is configured to sense a parameter indicative of arc formation in one of the branch breakers. The load center further comprises a solid-state main breaker coupled to receive a trigger signal from the at least one sensor. The solid-state main breaker is configured to determine whether the trigger signal satisfies a predefined arcing condition and, in response, temporarily interrupt current flow to the plurality of branch breakers and wait for a predefined event before restoring current flow to the plurality of branch breakers.
In accordance with any one or more of the foregoing embodiments, the at least one sensor comprises one sensor coupled to each of the plurality of branch breakers or one sensor coupled to multiple ones of the plurality of branch breakers.
In accordance with any one or more of the foregoing embodiments, the at least one sensor includes a voltage sensor and the parameter is voltage induced by arc formation in one of the branch breakers, and the load center further comprises a signal conditioning circuit connected to the voltage sensor, or the at least one sensor includes a radio frequency sensor and the parameter is radio frequency energy generated by arc formation in one of the branch breakers.
In accordance with any one or more of the foregoing embodiments, the predefined event is one of a predefined time period or an immediately next zero-crossing of a load center voltage, and the predefined time period is a half cycle of a load center current.
In general, in another aspect, embodiments of the present disclosure relate to a main breaker for a load center. The main breaker comprises, among other things, a solid-state trip switch configured to provide current flow to a plurality of branch breakers, and a breaker controller configured to control switching of the solid-state trip switch. The breaker controller is operable to receive a trigger signal resulting from a fault condition in one of the branch breakers and determine whether the trigger signal satisfies a predefined condition. The breaker controller is further operable to temporarily interrupt current flow to the branch breakers and wait for a predefined event before restoring current flow to the branch breakers in response the trigger signal satisfying the predefined condition.
In accordance with any one or more of the foregoing embodiments, the predefined condition is one of a predefined logic level or a predefined arcing condition, and the predefined arcing condition includes the trigger signal having one or more of a predefined waveform, shape, amplitude, and duration.
In accordance with any one or more of the foregoing embodiments, the trigger signal is received from at least one sensor coupled the branch breakers and represents one of a voltage induced by arc formation in one of the branch breakers or radio frequency energy generated by arc formation in one of the branch breakers.
In accordance with any one or more of the foregoing embodiments, the predefined event is one of a predefined time period or an immediately next zero-crossing of a main breaker voltage, and the predefined time period is a half cycle of a main breaker current.
In general, in yet another aspect, embodiments of the present disclosure relate to a method of suppressing arc formation in a load center. The method comprises, among other things, receiving, at a main breaker, a trigger signal resulting from a fault condition in one of a plurality of branch breakers in the load center, and determining, at the main breaker, whether the trigger signal satisfies a predefined condition. The method further comprises temporarily interrupting, at the main breaker, current flow to the plurality of branch breakers in response to the trigger signal satisfying the predefined condition, and restoring, at the main breaker, current flow to the plurality of branch breakers after occurrence of a predefined event.
In accordance with any one or more of the foregoing embodiments, the method further comprises coupling a sensor to each of the plurality of branch breakers or coupling at least one sensor to multiple ones of the plurality of branch breakers.
In accordance with any one or more of the foregoing embodiments, the predefined condition is one of a predefined logic level or a predefined arcing condition, and the predefined arcing condition includes the trigger signal having one or more of a predefined waveform, shape, amplitude, and duration.
In accordance with any one or more of the foregoing embodiments, the trigger signal is received from at least one sensor coupled the branch breakers, further comprising conditioning the trigger signal at a signal conditioning circuit connected to the at least one sensor.
In accordance with any one or more of the foregoing embodiments, the trigger signal represents one of a voltage induced by arc formation in one of the branch breakers or radio frequency energy generated by arc formation in one of the branch breakers.
In accordance with any one or more of the foregoing embodiments, the predefined event is one of a time period equal to a half cycle of a load center current, or an immediately next zero-crossing of a load center voltage.
A more detailed description of the disclosure, briefly summarized above, may be had by reference to various embodiments, some of which are illustrated in the appended drawings. While the appended drawings illustrate select embodiments of this disclosure, these drawings are not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.
Identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. However, elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.
Referring now to
As
In the
In general operation, when an arc begins to form in one of the branch breakers 104 (i.e., because that breaker has tripped), the sensor 112 for that breaker detects the electromagnetic field generated by the arc and outputs a corresponding signal. This trigger signal is then conditioned (e.g., smoothed, filtered, amplified, etc.) by a signal conditioner circuit 114 as needed, then sent to the main breaker 106 for further processing. The main breaker 106 processes the trigger signal to determine whether the signal satisfies a predefined condition that indicates arc formation. The determination may include, for example, whether the signal has a waveform that resembles a certain pattern and/or shape, whether the signal exceeds a certain amplitude, duration, and/or other threshold, and the like. If the trigger signal satisfies the condition or conditions indicative of arc formation, the main breaker 106 cuts current flow to the busbars 110 by opening the trip switch to the power line 108. Without current flow to sustain it, the arc loses energy and quickly dissipates, resulting in significantly less damage to the branch breaker 104 than would otherwise occur.
After a brief wait period, the main breaker 106 closes the trip switch for the power line 108 to restore current flow to the busbars 110. As alluded to earlier, the time period that the main breaker 106 waits before restoring current flow is long enough to allow the tripped branch breaker 104 to clear, but short enough to avoid adversely affecting electronic devices on other branch breakers 104 (e.g., causing the devices to abruptly shut down). In some embodiments, the main breaker 106 bases this wait period on a predefined event, such as an immediately next zero-crossing of the load center voltage, a fixed amount of time (e.g., a half cycle of the load center current), and other predefined events that are suitably short to avoid adversely affecting electronic devices. In preferred embodiments, the wait period is less than 8 milliseconds (msec), as a current loss of less than 8 msec does not adversely affect most electronic devices.
The main breaker 106 needs to have extremely fast switching times in order to perform the above current flow interruption, wait period, and restoration. Therefore, in preferred embodiments, the main breaker 106 is a type of breaker that uses a solid-state trip switch, such as a silicon carbide (SiC) transistor-based trip switch. Silicon carbide transistors, such as SiC MOSFET and Si CoolMOS, have extremely fast switching times (e.g., tswitch<1 μsec) and low drain-source resistance (e.g., Rds(on)<1 mΩ) at full current load, and thus are well suited for use as a main breaker in the load center embodiments herein. Commercially available examples include solid-state digital circuit breakers available from Atom Power, Inc., of Charlotte, N.C. These Atom Power intelligent digital circuit breakers can reportedly switch up to several thousand times faster than conventional thermal-mechanical circuit breakers.
Conventional thermal-mechanical circuit breakers, on the other hand, are well suited for use as the branch breakers 104, which do not require sub-microsecond switching times for normal operations. Examples include molded case circuit breakers (MCCB), miniature circuit breakers (MCB), and other commonly-used load center circuit breakers. Indeed, in alternative embodiments of the load center 102, the branch breakers 104 need not be breakers at all, but may instead resemble simple relay switches. Such simple relay switches only need to satisfy switching duty ratings (e.g., 120V/240V, 15 A, 20 A, etc.), as fault protection and other more traditional breaker functionality could be provided by the main breaker 106. Preferably the relay switches are remotely operable to allow them to be set/reset via a wired or wireless connection, an Internet connection, or other remote connections.
An exemplary signal conditioner circuit 114 is shown in
The above signal conditioner circuit 114 operates to amplify any voltage at the op-amp non-inverting input (i.e., from sensor 112) and outputs the amplified signal as a trigger signal to the main breaker 106. The main breaker 106, as discussed above, comes from a line of solid-state digital circuit breakers with extremely fast switching times. These intelligent digital breakers typically have a breaker controller 200 and a silicon-carbide transistor-based trip switch 202, among other components. The breaker controller 200 is programmed to provide various breaker functionality, including current and voltage monitoring, fault detection, and the like. When a fault condition is detected, such as a short-circuit or an overcurrent, the breaker controller 200 outputs a command to the trip switch 202 to shut off current flow to the busbars 110 (e.g., by turning off one or more transistors that form the trip switch).
In accordance with embodiments of the present disclosure, the breaker controller 200 may also be programmed with an arc detector module 204 that provides arc detection functionality. When the trigger signal is received by the breaker controller 200, the arc detector module 204 determines whether the trigger signal satisfies a predefined condition indicative of arc formation (e.g., matches a certain pattern and/or shape, exceeds a certain amplitude and/or duration, etc.). Such a predefined condition may be derived, for example, by tripping one of the branch breakers 104 in a controlled setting and analyzing the resulting signal generated by the sensor 112 and signal conditioner circuit 114. If the trigger signal satisfies the condition or conditions that indicate arc formation, then the arc detector module 204 causes the breaker controller 200 to interrupt current flow to the busbars 110. The detector module 204 thereafter causes the breaker controller 200 to wait for occurrence of a predefined event (e.g., next voltage zero-crossing, time interval of a current half cycle, etc.), then restore current flow to the busbars 110 (e.g., by turning on one or more transistors that form the trip switch).
When a fault condition occurs, logic within the trip unit of the electronic trip circuit breakers 310 detects the fault condition and outputs a trip signal that actuates the trip mechanism. This trip signal may be tapped and sent as a trigger signal to the main breaker 106 over a suitable connection 312 (e.g., shielded twisted-pair). Upon receiving the trip/trigger signal, the main breaker 106 again checks whether signal meets a predefined conditioned before cutting current flow. In this embodiment, the predefined condition can be simply whether the trip/trigger signal satisfies a predefined logic level, such as a logic high (or low) level. The main breaker 106 does not need to determine whether the signal satisfies a predefined condition indicative of arc formation before cutting current flow. Indeed, depending on the particular implementation, it may be possible for current flow to be cut even before the current-carrying contacts of the trip mechanism begin to separate (i.e., before arc formation can begin). Such an arrangement allows the main breaker 106 to perform a type of preemptive suppressing of arc formation.
Thus far, the embodiments disclosed herein have been described with respect to an electrical distribution panel or load center. However, the principles and teachings discussed herein are equally applicable to other types of electrical distribution arrangements, such as a motor control center (MCC), switchgear, and the like. It should therefore be understood that other types of electrical distribution arrangements besides load centers are within the scope of the present disclosure.
Referring now to
Upon receipt of the trigger signal, the main breaker determines whether the trigger signal satisfies a predefined condition at block 404. In some embodiments, the predefined condition is indicative of arc formation, such as whether the signal has a waveform that resembles a certain pattern and/or shape, whether the signal exceeds a certain amplitude, duration, and/or other threshold, and the like. In other embodiments, the predefined condition is a certain logic level. If the determination is no, then main breaker returns to block 402 and continues to monitor the load center for receipt of the trigger signal.
If the determination is yes, then the main breaker temporarily interrupts current flow to the busbars in the load center at block 406. The main breaker thereafter waits at block 408 for occurrence of a predefined event, such as an immediately next zero-crossing of the load center voltage, a fixed amount of time, such as a half cycle of the load center current, and the like. In either case, the wait period should be long enough to allow the tripped branch breaker to clear, but short enough to avoid adversely affecting the electronic devices on other branch breakers. Upon occurrence of the predefined event, the main breaker restores current flow to the busbars of the load center at block 410, and returns to block 402 for continued monitoring of the branch breakers.
Referring first to
In
In the preceding, reference is made to various embodiments. However, the scope of the present disclosure is not limited to the specific described embodiments. Instead, any combination of the described features and elements, whether related to different embodiments or not, is contemplated to implement and practice contemplated embodiments. Furthermore, although embodiments may achieve advantages over other possible solutions or over the prior art, whether or not a particular advantage is achieved by a given embodiment is not limiting of the scope of the present disclosure. Thus, the preceding aspects, features, embodiments and advantages are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s).
The various embodiments disclosed herein may be implemented as a system, method or computer program product. Accordingly, aspects may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to as a “circuit,” “module” or “system.” Furthermore, aspects may take the form of a computer program product embodied in one or more computer-readable medium(s) having computer-readable program code embodied thereon.
Any combination of one or more computer-readable medium(s) may be utilized. The computer-readable medium may be a non-transitory computer-readable medium. A non-transitory computer-readable medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the non-transitory computer-readable medium can include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. Program code embodied on a computer-readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.
Computer program code for carrying out operations for aspects of the present disclosure may be written in any combination of one or more programming languages. Moreover, such computer program code can execute using a single computer system or by multiple computer systems communicating with one another (e.g., using a local area network (LAN), wide area network (WAN), the Internet, etc.). While various features in the preceding are described with reference to flowchart illustrations and/or block diagrams, a person of ordinary skill in the art will understand that each block of the flowchart illustrations and/or block diagrams, as well as combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer logic (e.g., computer program instructions, hardware logic, a combination of the two, etc.). Generally, computer program instructions may be provided to a processor(s) of a general-purpose computer, special-purpose computer, or other programmable data processing apparatus. Moreover, the execution of such computer program instructions using the processor(s) produces a machine that can carry out a function(s) or act(s) specified in the flowchart and/or block diagram block or blocks.
The flowchart and block diagrams in the Figures illustrate the architecture, functionality and/or operation of possible implementations of various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
It is to be understood that the above description is intended to be illustrative, and not restrictive. Many other implementation examples are apparent upon reading and understanding the above description. Although the disclosure describes specific examples, it is recognized that the systems and methods of the disclosure are not limited to the examples described herein, but may be practiced with modifications within the scope of the appended claims. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than a restrictive sense. The scope of the disclosure should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.
