INTERCONNECTIONS USING RFID DEVICES

BACKGROUND

[0001] The inventive subject matter relates to electrical power equipment and, more particularly, to apparatus and methods for monitoring electrical connections.

[0002] A common source of failure in electrical power systems is degraded or failed connections between components, such as bus bar or cable connections. Complex electrical systems and components, such as switchgear or uninterruptible power supplies (UPSs) used in data centers, may have large numbers of such connections. These connections may by located in areas that are difficult and/or dangerous to access due to high voltage or other hazards.

[0003] Monitoring and maintaining such connections may be expensive and time consuming. Testing, such as infrared (IR) sensing based testing, may be used to locate suspect joints by identifying, for example, improperly torque bolts or thermal hot spots that may indicate loose or corroded connections. However, such testing may be disruptive to operations, time consuming and labor intensive. Such testing may also require operating equipment with protective doors or covers removed, which may increase hazards for personnel and require the use of special protective equipment. Such testing may also yield inadequate information, as the testing may only provide a snapshot of current conditions and little in the way of predictive information.

SUMMARY

[0004] Some embodiments of the inventive subject matter provide an apparatus including a voltage sensor circuit coupled to first and second components of an electrically conductive assembly and configured to generate an output signal representative of a voltage between the first and second components. The apparatus further includes a radio frequency (RF) transmitter circuit configured to receive the output signal and to transmit a radio signal representative of the voltage. The first and second components may include, for example, respective first and second mechanically connected conductors, e.g., first and second conductors bolted together. In some embodiments, the first and second components may be coupled via more than one interconnection of conductors. In some components the first and second components may be components of a single conductor (e.g., a wire or bus bar) or a fuse. The RF transmitter circuit may be included in a radio frequency identification (RFID) tag integrated circuit.

[0005] Further embodiments provide an apparatus including a substrate, an RFID tag integrated circuit supported by the substrate, and at least one electrically conductive member mechanically attached to the substrate, electrically coupled to a signal input of the RFID tag integrated circuit and configured to be electrically coupled to an external electrical conductor. The at least one conductive member may include, for example, a foil, a wire, a spring contact and/or a pin.

[0006] Further embodiments provide a housing configured to support the substrate and to conform to an outer surface of a cable and/or a ferrule of a cable connector. The at least one conductive member may include at least one conductive pin supported by the housing and configured to contact a conductor of the capable and/or the ferrule.

[0007] Some embodiments provide methods including receiving a signal indicative of a voltage between first and second components of an electrically conductive assembly and determining a status of an interconnection between the first and second components responsive to the received signal. Receiving a signal indicative of a voltage between first and second components of an electrically conductive assembly may include receiving the signal from an RFID tag electrically coupled to the first and second components.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a schematic diagram illustrating a monitoring system according to some embodiments of the inventive subject matter.

[0009] FIG. 2 is a schematic diagram illustrating a monitoring system implemented in an electrical equipment assembly according to some embodiments of the inventive subject matter.

[0010] FIGs. 3A and 3B illustrate a monitoring system for a bus bar assembly according to some embodiments of the inventive subject matter.

[0011] FIG. 4 illustrates a monitoring system for a bus bar assembly according to further embodiments of the inventive subject matter.

[0012] FIG. 5 illustrates a monitoring system of a cable/bus bar assembly according to some embodiments of the inventive subject matter.

[0013] FIG. 6 is a schematic diagram illustrating a monitoring system for a fuse according to some embodiments of the inventive subject matter. [0014] FIG. 7 is a schematic diagram illustrating a monitoring system for a conductor according to some embodiments of the inventive subject matter.

[0015] FIG. 8 is a schematic diagram illustrating a monitoring system with a thermocouple connection according to some embodiments of the inventive subject matter.

[0016] FIG. 9 is a schematic diagram illustrating a monitoring system in an electrical equipment assembly according to further embodiments of the inventive subject matter.

[0017] FIG. 10 illustrates a monitoring system for a cable assembly according to further embodiments o the inventive subject matter.

[0018] FIG. 1 1 illustrates a portion of the monitoring system of FIG. 10 according to some embodiments of the inventive subject matter.

[0023] FIG. 12 illustrates application of a multi-channel monitoring system to cable interconnections according to some embodiments of the inventive subject matter.

[0024] FIG. 13 is a schematic diagram illustrating an antenna-ground plane arrangement for monitoring system according to some embodiments of the inventive subject matter.

[0025] FIG. 14 is a schematic diagram illustrating an antenna-ground plane arrangement for monitoring system according to further embodiments of the inventive subject matter.

[0026] FIG. 15 is perspective view of a monitoring system according to some embodiments of the inventive subject matter.

DETAILED DESCRIPTION

[0027] Specific exemplary embodiments of the inventive subject matter now will be described with reference to the accompanying drawings. This inventive subject matter may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive subject matter to those skilled in the art. In the drawings, like numbers refer to like elements. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. As used herein the term "and/or" includes any and all combinations of one or more of the associated listed items. [0028] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the inventive subject matter. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms "includes," "comprises," "including" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

[0029] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive subject matter belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0030] The inventive subject matter may be embodied as apparatus, methods and computer program products. Some embodiments may be described with reference to block diagrams and/or operational illustrations that illustrate structures and operations. Blocks of the block diagrams and/or operational illustrations may generally implemented using electric circuits configured to perform the specified functions. These "circuits" may generally be implemented using analog and/or digital circuitry and may include discrete components and/or integrated components, such as data processing integrated circuits (e.g.,

microprocessors, microcontrollers, digital signal processors and the like) and application- specific integrated circuits (ASICs).

[0031 ] Each block in such diagrams may represent a module, segment, or portion of computer-executable program code for implementing the specified logical function(s).

Computer-executable program code may be provided one or more data processors, special purpose processors, ASICs, and/or other programmable data processing apparatus, such that the instructions, which execute to the code to provide the functions/acts specified in the block diagrams and/or operational block or blocks and thus provide circuits that perform such functions/acts.

[0032] These computer-executable program code may also be stored in a non- transitory medium that may direct a data processor to function in a particular manner, such that the program code stored in the non-transitory medium constitute an article of manufacture including instructions that implement the functions specified in the block or blocks of the block diagrams and/or operational illustrations. The non-transitory medium may be, but is not limited to, an electronic, magnetic, optical, electromagnetic, or semiconductor system, apparatus, or device. More specific examples (a non-exhaustive list) of the non-transitory medium include the following: hard disk devices, optical storage devices, magnetic storage devices, random access memory (RAM) devices, read-only memory (ROM) devices, erasable programmable read-only memory (EPROM or Flash memory) devices, and compact disc read-only memory (CD-ROM).

[0033] FIG. 1 illustrates a system 100 according to some embodiments. The system includes a radio frequency identification (RFID) tag 1 10 configured to detect a voltage between first and second conductors 1 12a, 1 12b coupled to respective components 10a, 10b of a conductive connection 10. The connection 10 may include any of a number of different types of electrical connections. The components 10a, 10b may include, for example, bus bars, wires, cables, terminal blocks, switch contacts, and/or other components in electrical continuity therewith. The components 10a, 10b may be joined using any of a number of different types of connection, such as bolted connections, clamped connections, soldered connections, welded connections, and the like. The connections maybe fixed, such as connections between bus bars, wires or similar connections, or contingent, such as connections between switch contacts. The conductors 1 12a, 112b for connecting to the connection components 10a, 10b may include any of a number of different types of conductors, such as wires, spring contacts, and the like.

[0034] The RF ID tag 1 10 may include any of a number of types of integrated circuit devices configured to measure a voltage between terminals and to transmit a measurement of that voltage in association with a RFID. In some embodiments, such devices may include passive RFID integrated circuit devices that are powered using RF transmissions, such as the Texas Instruments TMS37157 Passive Low Frequency Interface Device (PaLFI) or the IC Magic Inc. IDS-SL900A EPCglobal Class 3 tag chip. In some embodiments, RFID integrated circuit devices powered by batteries or other power sources may be used.

[0035] FIG. 2 illustrates an exemplary implementation of such an apparatus in a piece of electrical equipment 200, such as a switchgear assembly or uninterruptible power supply (UPS). Respective RFID tags 1 10 are coupled to components of respective electrical connections 10. An RFID controller/reader 130 is configured to provide power to and communicate with the RFID tags 1 10 via an antenna 120. In particular, the RFID tags 1 10 may be activated by the RFID controller/reader 130 using radio frequency inductive power transfers via the antenna 120, and the RFID tags 1 10 may responsively perform voltage measurements on the associated connections 10 and transmit measurement data to the RFID controller/reader 130 via the antenna 120. The radio transmissions from the RFID tags 1 10 may associate RFIDs with voltage measurements made across the respective connections 10 by the RFID tags 1 10, thus facilitating monitoring and analysis of the connections 10.

[0036] The RFID controller/reader 130 may convey the measurement data and/or related information to a system controller 140 and/or an external device, such as a computer, which may use the information to determine status of the connections 10. For example, a bus bar connection operating under normal conditions at a nominal current level may exhibit a relatively small voltage, e.g., on the order of less than 10 millivolts, under normal conditions. If this voltage starts to increase to, for example, tens of millivolts, this may indicate increasing connection resistance caused by looseness and or corrosion and increased probability of failure, even if the increased connection resistance has yet to result in overheating or other signs of impending failure. Thus, the connection voltage measurement may serve as a leading indicator of increased risk of failure of the connection and may be more useful than temperature monitoring or other techniques that may not detect incipient failure conditions in sufficient time to initiate actions to prevent damage.

[0037] Monitoring trends in voltage measurements for connections may allow the system controller 140 or an external monitoring device to determine when there is an increased likelihood of a connection failure, and generate alerts to maintenance systems and/or personnel to initiate corrective actions, such as tightening and/or cleaning connections. The system controller 140 and/or external monitoring device may use various techniques to analyze trends, filter out false readings and generate alarms. For example, the system controller 140 and/or external monitoring device may be configured to identify and filter out connection voltage measurements that are spurious and/or associated with conditions in which the connection is not active. The system controller 140 and/or external monitoring device may also be configured to perform statistical analyses that can more accurately detect incipient failures from the raw connection voltage measurements.

[0038] The use of RFID tags 1 10 to make such voltage measurements enables identification of exact locations of potential problems, as each connection may be associated with an RFID. The monitoring does not require opening of equipment enclosures or other more invasive actions that can be dangerous to personnel. Because RFID tags that do not require wired power or communications connections can be used, they can generally be installed where desired, including less accessible locations. Existing equipment can be retrofitted to provide connection monitoring without undue cost or complex modifications.

[0039] FIGs. 3 A and B illustrate a RFID tag system 300 according to some embodiments. The system 300 includes an RFID integrated circuit 320 mounted on a printed circuit board (PCB) 310 Connection to a first connection component may be provided by a conductive tab 330a on a bottom side of the PCB 310 and/or a spring contact 330b at a side of the PCB 10. Connection to a second connection component may be provided by another spring contact 340b and/or a pin 340b to which a wire lead may be attached.

[0040] FIG. 4 illustrates one application of the RFID tag 300 of FIG. 3 to a connection between first and second bus bars 10a, 10b. Contact to the first bus bar 10a is made through the spring contact 340a. Contact to the second bus bar 10b is made through the conductive tab 330a, which is attached to the second bus bar 10b using a spring clip 332.

[0041] FIG. 5 illustrates an application of the RFID tag 300 of FIG. 3 to a connection between a bus bar 10a and a wire 10b. Contact to the bus bar 10a is made through the conductive tab 330a, which is attached to the bus bar 10a using a spring clip 332. Contact to the wire 10b is made using a wire lead 350 connected to the pin 340b and to a cable tie 360 that includes a contact configured to penetrate insulation of the wire 10b to make electrical contact.

[0042] It will be appreciated that RFID tag systems according to other embodiments may use a variety of di fferent physical arrangements than those illustrated in FIGs. 3-5. Some embodiments may use RFID integrated circuits that are battery-powered and may provide increased transmission range and/or data processing capabilities in comparison to RF-powered devices. Some embodiments may utilize RFID tags installed in equipment without an embedded controller/reader, with the RFID tags instead being accessed using test/maintenance equipment that performs the controller/reader functions.

[0043] According to further aspects, RFID tags may be similarly used to monitor other states and parameters of an electrical apparatus, such as fuse integrity, conductor current, temperature, humidity, and the like. For example, FIG. 6 illustrates the use of an RFID tag 610 to monitor integrity of a fuse 20 using conductors 612a, 612b electrically connected to ends of the fuse 20. FIG. 7 illustrates the use of an RFID tag 710 to monitor a voltage across a segment 30a of a conductor 30 using conductors 712a, 712b connected to ends of the segment 30a. Resistance of the segment 30a is known, such that a voltage measurement across the segment 30a may be used to determine a current flowing through the conductor 30. A similar technique may be used to monitor temperature, e.g., by connecting voltage inputs of an RFID tag to a thermistor or other temperature sensitive resistance. FIG. 8 illustrates a system 800 that uses an RFID tag 810 coupled by leads 812a, 812b to a thermocouple 40. Such an arrangement may not require application of a bias to the temperature sensing element to provide temperature sensing. In some embodiments, the RFID tag 810 may include an onboard temperature sensor, which may provide temperature sensing within the operating limits of the RFID tag 810.

[0044] FIG. 9 illustrates an exemplary implementation of such an apparatus in a piece of electrical equipment 900, such as a switchgear assembly or uninterruptible power supply (UPS). Respective RFID tags 1 10 are coupled to electrical connections 10, conductors 30, fuses 20 and temperature sensors 40. An RFID controller/reader 130 is configured to provide power to and receive transmissions from the RFID tags 1 10 via an antenna 120. The transmissions from the RFID tags 1 10 associate RFIDs with voltage measurements made across the respective connections 10 by the RFID tags 1 10. The RFID controller/reader 130 may convey this information to a system controller 140 and/or an external device, such as a computer, to enable monitoring of the devices coupled to the RFID tags 1 10.

[0045] FIGs. 10 and 11 illustrate an RFID tag apparatus and application therefor according to further embodiments. An RFID tag apparatus 1100 includes a housing 1110 configured to support a printed circuit board assembly 1 130 that may include an RFID tag (e.g., an RFID tag integrated circuit and peripheral circuitry therefor). The housing 1 1 10 has a trough 1120 defined therein that is configured to conform to an outer surface of a cable 60 and a ferrule 72 of a cable connector (e.g., lug) 70. First and second conductive pins 1 140 are supported by the housing 1 1 10 and electrically coupled to the RFID tag of the circuit board assembly 1 130. The pins 1 140 are configured to contact a conductor of the cable 60 (e.g., by piercing through insulation) and the ferrule 72 when the housing 1 1 10 is compressed against the cable 60 and connector ferrule 70 using, for example, cable ties 80, shrink wrap or other binding. The RFID tag apparatus 1 100 may be configured to sense a voltage between the conductor of the cable 60 and the ferrule 72 and to transmit information to an external device based on this voltage so that the external device may determine, for example, the integrity of the connection between the cable 60 and the connector 70. As further illustrated in FIG. 10, an additional RFID tag assembly 300 may be used to monitor connections between the connector 70 and a bus bar 10 to which it is connected.

[0052] FIG. 12 illustrates an exemplary use of a multi-channel monitoring apparatus according to some embodiments. A first channel of an RFID tag based monitoring apparatus 1200 may be used to monitor a connection between a first cable 60a and a bus bar 10. A second channel of the monitoring apparatus 1200 may be used to monitor a connection between a second cable 60b and the bus bar 10. It will be understood that such multi-channel monitor apparatus may be used in other applications, e.g., such a monitoring apparatus may be used to monitor cable-to-ferrule and ferrule-to-bus bar connections for a single cable.

[0046] According to further aspects, RFID tag-based monitoring apparatus may use any of a number of different mechanical arrangements, such as different antenna and ground plane layouts. For example, FIG. 13 illustrates an RFID tag monitoring apparatus 1300 including a planar circuit assembly 1310, e.g., a polyimide, ceramic or other substrate with one or more RFID tag integrated circuits and associated circuitry mounted thereon, along with a ground plane 1310 and a vertical monopole 1330 supported by the circuit assembly 1310.

[0047] FIG. 14 illustrates a monitoring apparatus 1400 with a different configuration, including a planar circuit substrate 1410, ground plane 1420 and a planar antenna 1430 positioned above the circuit assembly 1410 on a standoff or other structure. FIG. 15 illustrates a monitoring apparatus 1500 including such a structure, including a planar circuit assembly 1510 with an underlying ground plane 1520 and a planar antenna 1530.

[0048] Monitoring apparatus and methods according to various embodiments of the inventive subject matter may be used to support a variety of different diagnostic and/or prognostic functions. For example, voltage readings of conductor connections performed by RFID tag-based apparatus along the lines described above may be logged over a period of time and analyzed to identify trends indicative of connection degradation and/or increased likelihood of failure. Such information may be used, for example, to inform preventative maintenance operations and/or to trigger more detailed testing or inspection. Similar techniques may also be used to identify status trends in conductors and/or conductive elements, such as fuses, or contingently conductive devices, such as switches, to identify conditions such as fuse degradation or increased contact resistance.

[0049] In the drawings and specification, there have been disclosed exemplary embodiments of the inventive subject matter. Although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the inventive subject matter being defined by the following claims.