SYSTEM AND METHOD FOR IN-CABINET HEALTH MONITORING

A system comprises a set of power conversion components powered by a power line system, and a time domain reflectometry apparatus coupled to the power line system. The time domain reflectometry apparatus is configured to acquire a reflection signal that results from reflection of an incident signal injected on the power line system, compute a difference signal based on the reflection signal and a baseline signal, and detect a fault in the set of power conversion components based on the difference signal and a fault pattern.

BACKGROUND INFORMATION

The subject matter disclosed herein relates to power converters and to apparatus and techniques to monitor the health of power conversion system components.

BRIEF DESCRIPTION

In one aspect, a system comprises a set of power conversion components powered by a power line system, and a time domain reflectometry apparatus coupled to the power line system. The time domain reflectometry apparatus is configured to acquire a reflection signal that results from reflection of an incident signal injected on the power line system, compute a difference signal based on the reflection signal and a baseline signal, and detect a fault in the set of power conversion components based on the difference signal and a fault pattern.

In another aspect, a method comprises acquiring a reflection signal that results from reflection of an incident signal injected on a power line system that powers a set of power conversion components, computing a difference signal based on the reflection signal and a baseline signal, and detecting a fault in the set of power conversion components based on the difference signal and a fault pattern.

In a further aspect, a non-transitory computer-readable medium has computer-executable instructions which, when executed by a processor, cause the processor to acquire a reflection signal that results from reflection of an incident signal injected on a power line system that powers a set of power conversion components, compute a difference signal based on the reflection signal and a baseline signal, and detect a fault in the set of power conversion components based on the difference signal and a fault pattern.

DETAILED DESCRIPTION

Referring now to the figures, several embodiments or implementations are hereinafter described in conjunction with the drawings, wherein like reference numerals are used to refer to like elements throughout, and wherein the various features are not necessarily drawn to scale.

FIG.1shows a power conversion system100with an SSTRD device and a switch circuit. The example system is a power conversion system or power converter having a cabinet102, such as a motor control center (MCC), with an interior that houses a set of power conversion components104,106, and108, which are powered by a power line system110. In the illustrated example, the power line system110is a three-phase system having multiple power lines L1, L2, and L3. In other implementations, a single phase power line system can be used (e.g., having two lines), or more than three phases can be used. The system100converts input power from the power line system110to deliver output power to drive a multiphase load, such as a three phase motor112. In the illustrated implementation, the set of power conversion components includes a three-phase motor drive104, a circuit breaker106, and fuses108. In one example, the motor drive112is a variable frequency drive (VFD).

The motor drive104is powered by the power line system110, and is coupled to the power lines L1, L2, and L3through a three-phase circuit breaker106, and three in-line fuses108. The motor control center102in one example includes multiple enclosed sections having a common power bus and with individual sections having a combination starter that includes a motor starter, fuses, and/or circuit breaker, and power disconnect (not shown). In addition to one or more motor drives104, various implementations of the motor control center102can also include push buttons, indicator lights, programmable logic controllers, and metering equipment (not shown), and the MCC102may be combined with an electrical service entrance for a facility. In one example, individual motor control units or sections include a circuit breaker106, fuses108, and a VFD motor drive104as shown inFIG.1. The health of the power line in the system100is important for commercial and/or industrial operations, wherein faults (e.g., breaker trips, blown fuses, loosening of wire connections, cable degradation or overheating, motor starter performance degradation, motor control contactor and control operation, load switch operation, etc.) can impact the commercial or industrial operation.

The described examples provide health monitoring apparatus, including a time domain reflectometry apparatus120coupled to the power line system110. The time domain reflectometry apparatus120in one example is a spread spectrum time domain reflectometry (SSTDR) apparatus or device. The apparatus120, moreover, advantageously operates while the power conversion components104,106, and108are powered and operating to drive the motor112, referred to as “live wire” health monitoring, even for constrained installations (e.g., power line cable lengths of less than about 1 m, high voltage, high current, and in-cabinet features). In one implementation, the time domain reflectometry apparatus120is operatively coupled to a computer122, for example, by appropriate communications network interconnections and cabling of any suitable type and protocol. In one example, the apparatus120and/or the computer122include one or more internal processors and associated electronic memory or other non-transitory computer-readable that store computer-executable instructions which, when executed by the processor or processors, implement a health monitoring program as described further hereinafter.

The time domain reflectometry apparatus120in one example is configured to generate and provide an incident signal to one or more of the power lines of the power line system110during operation of the motor drive power conversion system100, and acquire one or more respective reflection signals that result from reflection of the incident signal injected on the power line system110. In addition, the time domain reflectometry apparatus120is configured to compute a difference signal based on the reflection signal and a baseline signal, and detect a fault in the set of power conversion components104,106, and/or108based on the difference signal and a fault pattern. In the illustrated example, the time domain reflectometry apparatus120is also configured to identify a suspected one of the set of power conversion components104,106, and/or108that is suspected of being the source, based on the detected fault. In certain examples, the time domain reflectometry apparatus120is configured to determine a type of the detected fault as being a persistent fault or an intermittent fault. In these or other examples, the time domain reflectometry apparatus120is configured to adapt or otherwise adjust the fault pattern based on the detected fault.

In the example ofFIG.1, the time domain reflectometry apparatus120has a single channel, and the system100also includes a switch circuit124coupled between the time domain reflectometry apparatus120and the power line system110. The switch circuit124in one example is operated by the time domain reflectometry apparatus120to selectively coupled the single channel of the time domain reflectometry apparatus120to a selected one of the power lines L1, L2, L3of the power line system110for testing the selected power line. This configuration allows the time domain reflectometry apparatus120to sequentially perform reflectometry testing and assess the health of the individual power lines L1, L2, and L3of the system100in real time during operation of the system100to drive the motor112.

FIG.2shows another implementation of a power conversion system200having a three channel SSTRD device. In this example, the time domain reflectometry apparatus120has multiple channels individually coupled to a respective one of the power lines L1, L2, and L3of the power line system110. This example facilitates concurrent health monitoring of multiple power lines during operation of the system200to drive the motor112.FIG.3shows another power conversion system300including a circuit breaker320with an integrated SSTRD device that includes the three-phase circuit breaker106and the three channel SSTDR apparatus120as described above in connection withFIG.2. In this and other possible examples, the time domain reflectometry apparatus120is integrated into one of the power conversion components104,106, and/or108.

Referring also toFIGS.4-6,FIG.4shows the time domain reflectometry apparatus120during testing of one example power phase line L3in the system100.FIG.5shows a graph500having a curve501that shows reflected fault SSTDR data and a curve502that shows baseline SSTDR data as a function of distance from the SSTDR apparatus120in the configuration ofFIG.4during powered operation of the system100.FIG.6shows a graph600including a curve601that shows SSTDR difference data showing a subtractive difference between the fault data and the baseline data in the system100for the acquired data illustrated inFIG.5. In this example, a particular calibrated fault in one of the components104,106, or108of the system100generates reflected data corresponding to a distance D. At the distance D, the identifiable fault corresponds to difference data having a positive amplitude at or above a threshold611(TH1).

In one example for recognizing (detecting) and identifying an open circuit fault, the SSTDR apparatus120reports a fault with arrays of 92 raw data, and calculates or otherwise computes the difference (e.g., the difference curve600) by subtracting the baseline or reference (e.g., curve502) from the fault data (e.g., curve501). The time domain reflectometry apparatus120determines the fault amplitude threshold (e.g., 3% of baseline launch spot510at sample 9 inFIG.5). To bypass the launch spot510, starting from sample 13 in the graph500, the time domain reflectometry apparatus120looks for the peak which is greater than the fault threshold611(TH1). In one implementation for this example open circuit fault, the time domain reflectometry apparatus120determines a peak as such if there is a negative value in three samples to the left side and the right side of the peak. The time domain reflectometry apparatus120in one implementation stops further screening once it identifies the first such peak moving from left to right. In this example, only the one fault caused by a specific component which is close to the SSTDR time domain reflectometry apparatus120can be detected at a time, which is advantageous. In this example, for each waveform with a fault, only the first peak is evaluated, and all others thereafter are ripples and are not evaluated. Once the first peak is identified, the SSTDR time domain reflectometry apparatus120stops further evaluation and records the sample point of the peak for fault distance calculation, although it is less significant for constrained system. Based on the distance computation, the SSTDR time domain reflectometry apparatus120determines a fault name according to the peak amplitude to identify the likely source of the detected fault.

In one example fault distance calculation for an open circuit fault at 16.817 m, the SSTDR time domain reflectometry apparatus120identifies the point of peak as sample number 25, where the launch point is sample number 9 inFIGS.5and6. The time domain reflectometry apparatus120in this example computes a distance resolution in meters as 2.99.79 x 106* VoP/8*f, where VoP is the velocity of propagation of the line L3and f is the SSTRD measurement frequency in Hz. In one example, the fault distance calculation includes the time domain reflectometry apparatus120computes the distance D = µ(Sn-Z), where Snis the sample index number of the identified peak (e.g., 26) of the fault location, Z = 9 (e.g., the sample index number of the launch point510, the speed of light is 3 x 108m/s, the velocity of propagation VoP is 0.68, the SSTRD measurement frequency f is 2.4 x 107Hz, and the distance resolution (e.g., distance per sample) u is 1.06.

In the illustrated example, the system component of interest exhibits a discernible fault that is recognized or otherwise identified by the time domain reflectometry apparatus120during powered operation of the power phase line L3. SSTDR implementations advantageously facilitate injection and reflection detection for powered phase lines, for example, that provide AC power to operate the system components104,106, and108at a suitable line frequency, such as approximately 50 Hz, 60 Hz, etc.

Referring also toFIG.7, the time domain reflectometry apparatus120in one example is configured to render the detected fault on a user interface700, for example, implemented in the time domain reflectometry apparatus120and/or the computer122inFIGS.1-4above. The example user interface700is a graphical user interface that displays or otherwise renders a graphical indication702of the interconnection of the powered devices and the time domain reflectometry apparatus120in the system100, as well as a textual indication or rendering704of configuration parameters and time stamped descriptions of detected faults, in addition to a graphical representation or rendering706of SSTDR data associated with an incident signal and/or a reflected signal, alone or in addition to computed difference data and/or a calibrated fault pattern or profile associated with the system100.

FIG.8shows a diagnostic method800implemented in one example by the time domain reflectometry apparatus120alone or in combination with the computer122illustrated and described above. The method800in this example begins with unpowered baseline characterization and fault calibration at802-816, referred to as “dead wire calibration”. At802inFIG.8, the method800includes acquiring baseline SSTDR data in the system100while the system is unpowered (e.g., no supply voltages or currents are present in the power line system110). At804, a user or automated system sets a component fault, for example by turning off one, some or all phases of the circuit breaker106inFIG.1above. At806, the time domain reflectometry apparatus120generates and injects one or more signals into the unpowered power line system110and acquires SSTDR data (e.g., referred to as calibration fault data) while the system100remains unpowered and the applied fault remains set (e.g., the circuit breaker106remains turned off).

At808, the time domain reflectometry apparatus120calculates or otherwise computes the difference between the baseline and the calibration fault data, referred to as calibration difference data associated with a particular fault that is set. At810, the time domain reflectometry apparatus120determines a fault pattern for the applied fault (e.g., breaker open), and the time domain reflectometry apparatus120stores the associated fault pattern in a memory of the computer122and/or a memory of the time domain reflectometry apparatus120. At814, the user or automated system recovers the previously set fault (e.g., closes the circuit breaker106), and the time domain reflectometry apparatus120determines at816whether more components are to be calibrated or characterized (e.g., further faults are to be characterized in the system, whether of the previously calibrated component or of a further component. If so (YES at816), the method800returns to804-814as described above to characterize further component faults in the system100while the system remains unpowered. The dead wire calibration process repeats for each testable component and/or fault associated there with.

Once the desired component faults have been characterized during the dead wire calibration processing at802-814(e.g., NO at816), the method proceeds to baseline data acquisition while the system is powered, referred to as live wire baseline acquisition or capturing. At818inFIG.8, the user or automated system powers up the system100, for example, by turning main power on to all the system components, while not actively operating the power conversion components (e.g., while the motor drive104is not actively driving the motor load112). At820, the time domain reflectometry apparatus120acquires live wire baseline SSTDR data.

The method800then begins a continuously repeated live wire health monitoring loop, which continues in one example until a persistent fault is identified, leading to the system100shutting down pending maintenance or further analysis of the identified persistent fault. The example method800in this example also differentiates between persistent and intermittent faults in one or more of the calibrated system components, although not required for all possible implementations. The real time fault health monitoring, moreover, can be implemented alone or in combination with automated remedial actions responsive to certain identified faults, and numerous forms of reporting of the faults, for example, via the user interface (e.g.,FIG.7) and/or via network communications messaging to other devices in a networked factory automation system.

At822, the time domain reflectometry apparatus120acquires live wire SSTDR fault data, and computes difference data at824between the live wire baseline data acquired eight820, and the fault data acquired at822. At826, the time domain reflectometry apparatus120detects one or more faults. The live wire health monitoring in one implementation concurrently evaluates faults at822with respect to multiple calibrated faults, and certain implementations can concurrently identify multiple contemporaneous faults in the system100based on a single data acquisition at822. At824and826in one example, the time domain reflectometry apparatus120computes the difference (e.g., graph600), and detects the fault based on the calibrated fault patterns, and identifies at828which one caused the fault based on the previously stored fault patterns. In this regard, the time domain reflectometry apparatus120in one example uses stored profiles that represent what a certain type of fault might look like during operation of the system100, whether it is an open circuit or a degraded wire having different profiles, etc., and the time domain reflectometry apparatus120is configured to interpret the acquired live wire data and indicate any suspected faults and render such to the user interface or to a networked computer element associated with the computer122or the time domain reflectometry apparatus120. Continuing at828, the time domain reflectometry apparatus120determines whether any fault or faults have been detected in the current loop iteration, and if not (NO at828), the time domain reflectometry apparatus120performs another loop at822-828as previously described.

In response to detection of one or more faults (YES at828), the time domain reflectometry apparatus120determines a type for each detected fault at830. In this example, the time domain reflectometry apparatus120distinguishes between intermittent and persistent detected faults, for example, using a memory to indicate the presence or absence of each calibrated fault within a certain number of previous iterations of the loop822-828. In the illustrated implementation, if the time domain reflectometry apparatus120determines that a particular detected fault is intermittent (INTERMITTENT at830), the method800proceeds to832where the time domain reflectometry apparatus120reports the detected intermittent fault, for example, using the user interface features shown inFIG.7above alone or in addition to network messaging to notify a user or a networked computer within a factory automation system. In one example, the time domain reflectometry apparatus120adapts or otherwise adjusts one or more stored fault patterns based on the detected intermittent fault. The time domain reflectometry apparatus120in one example clears the detected fault at836, and returns to begin another live wire health monitoring loop at822-828as previously described.

If the time domain reflectometry apparatus120determines that a detected fault is persistent (PERSISTENT at830), the time domain reflectometry apparatus120reports the persistent fault at840, for example, via a user interface or network messaging, and the time domain reflectometry apparatus120adapts or otherwise adjusts one or more stored fault patterns at842based on the detected persistent fault. In the illustrated implementation, following this reporting and selective adaptation regarding a detected persistent fault, the example method800ends at844.

Various embodiments have been described with reference to the accompanying drawings. Modifications and changes may be made thereto, and additional embodiments may be implemented, without departing from the broader scope of the invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative rather than restrictive sense. The above examples are merely illustrative of several possible embodiments of various aspects of the present disclosure, wherein equivalent alterations and/or modifications will occur to others skilled in the art upon reading and understanding this specification and the annexed drawings. In addition, although a particular feature of the disclosure may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Also, to the extent that the terms “including”, “includes”, “having”, “has”, “with”, or variants thereof are used in the detailed description and/or in the claims, such terms are intended to be inclusive in a manner similar to the term “comprising”.