Metrology device including a high-voltage protection module

A high-voltage protection module for a metrology device includes a metal-oxide varistor (MOV) coupled across a mains power line, a resistor electrically coupled to the MOV in series with the MOV, and a fuse electrically coupled to the MOV and the resistor in series, the resistor being located between the fuse and the MOV. The fuse opens upon an overvoltage event disengaging alternating current (AC) power from the mains power line to the metrology device.

TECHNICAL FIELD

The present disclosure relates generally to utility meters. Specifically, the present disclosure relates to high-voltage protection systems and methods of a metrology device.

BACKGROUND

Utility metering units such as electric, water and gas meters are devices that measure the amount of the utility such as electricity, water, and gas consumed by a residence, a commercial building, or an electrically powered device. During the lifetime of a utility metering unit, the utility metering unit may be exposed to a myriad of environmental events and/or conditions that may impair or otherwise adversely affect the performance and functionality of the utility metering unit. Further, these environmental conditions may diminish the on-field longevity of the utility metering unit. Thus, the environmental conditions may result in higher costs to a utility provider and/or a utility consumer.

Still further, because the utility metering unit may be installed at a location outside a building such as a residential house or a commercial building, the utility metering units may not be electrically coupled to the building's internal breaker systems. This can result in the utility metering unit being at risk of being subjected to high voltage and environmental surges directly connected to the power grid to which the utility metering unit and the building's internal breaker systems are electrically coupled. This poses a significant risk to the utility metering unit, the building, and individuals in and around the building.

The environmental events and/or conditions the utility metering unit may be subjected to during field deployments may include a transient high voltage (HV) surge event including impulse and ringing waveforms. The cause of an HV surge event may include, for example, lightning, power line arching, or other high voltage instances. In another example, the environmental events and/or conditions the utility metering unit may be subjected to during field deployments may include abnormal overload conditions caused by end-of-life (EOL) and/or aging of on-board components such as metal-oxide varistors (MOVs) and other circuit protection devices. Further, in another example, the environmental events and/or conditions the utility metering unit may be subjected to during field deployments may include abnormal overvoltage conditions. The abnormal overvoltage conditions may be caused by, for example, power-grid voltage stability issues due to fluctuations in demand, among other causes.

DESCRIPTION OF EXAMPLE EMBODIMENTS

As mentioned above, a utility metering unit (also referred to herein as a “utility meter” or a “metrology device”) may be subjected to high voltage (HV) surge events and abnormal overload conditions that negatively affect the functioning and/or lifespan of the utility meter. In some instances, the utility meter may utilize power line communication (PLC) technologies to communicate with one or more of neighbor utility meters (also referred to herein as “nodes”) over PLC communication links within a network of utility meters. PLC communications technologies utilize a low ohmic connection to the mains terminals of the utility meters. Failure to include a PLC compatible connection can reduce communication performance and result in an inability to transfer data from the utility meters to a central office. Low ohmic connections utilize line-to-line voltage clamping to protect PLC front end communication devices from HV surge events and abnormal overload conditions, among other types of surge and transient events. These components that are connected line-to-line have failure modes that fail short. When a protection device fails short with no current limiting impedance, the utility meter enclosure including any and all components and devices of the utility meter are at risk of complete failure. Such a complete failure results in the loss of the entirety of the utility meter. This complete loss results in a relatively larger cost in replacement versus the replacement of failure components within the utility meter.

The failure components that serve as protection mechanisms that assist in avoiding a complete loss of the utility meter include metal-oxide varistors (MOVs) and other similar circuit protection devices. An MOV within a utility meter may be placed directly across the mains line in order to reduce clamping voltage (e.g., a let-through voltage). The clamping voltage defines what spike voltage may cause the protective components such as the MOV to short or “clamp.” A relatively lower clamping voltage may provide relatively better protection but may result in a shorter life expectancy for the overall protective system. The lowest three levels of protection defined in the Underwriters Laboratories (UL) rating are 330 V, 400 V and 600 V, for example. A standard let-through voltage for 120 V AC devices may be, for example, 330 volts.

In a first approach, a protection circuit including an MOV within a utility meter may be designed such that energy into the MOV is limited. This first approach assumes the MOV will short (e.g., fail) during its lifetime. This approach may result in increased costs of replacing the MOV itself as well as downtime for the utility meter and time spent by a service technician to replace the MOV.

A second approach may include designing the MOV itself such that it will not short (e.g., fail) in the first instance throughout the life of the utility meter. This second approach includes an MOV that is over-spec'd to increase the robustness of the MOV. However, some regulatory and product safety organizations (e.g., the National Electrical Manufacturers Association (NEMA)) have determined that a wear out mechanism within the MOV will result in even a relatively more robust MOV ultimately shorting or failing. Further, an MOV located directly across an electrical line may be considered by the regulatory and product safety organizations as a design point that may not be tolerated. For example, NEMA standard C12.30-2019 defines some of these standards.

Thus, the present systems and methods seek to address these issues based on the first approach described above. The systems and methods described herein include a fuse to protect from overvoltage situations that may cause the protection device to fail short. A series limiting resistor is included within the circuit associated with the MOV to allow the fuse to break currents with service voltages that would normally exceed the rating of the fuse.

Inclusion of a series limiting resistor in front of a fuse may not be necessary in some scenarios since most applications utilize an entirely low ohmic connection for efficiency or power demand. Communication modules do not draw significant amounts of power so the communication modules can tolerate some level of impedance. Further, selection of the components to ensure compliance in a metering environment may take into consideration that a specific resistor or fuse function within the protection circuit described herein is selected in order to control the failure chain.

Still further, in instances where the utility meter fails, the outgassing of various electrical components may occur. The outgassing of an electrical component may occur because of an HV surge event or abnormal overload condition where the physical and chemical properties of the electrical components including, for example, an MOV, are compromised. This may lead to the outgassing of the electrical component where the various gasses present in the packaging of the electrical component overcome external packaging and allow for chemicals to escape the packaging. For example, an MOV may contain a ceramic mass of zinc oxide grains, in a matrix of other metal oxides, such as small amounts of bismuth, cobalt, manganese oxides. These elements are sandwiched between two metal plates which constitute the electrodes of the MOV. The boundary between each grain and a neighbor forms a diode junction, which allows current to flow in only one direction. The accumulation of randomly oriented grains is electrically equivalent to a network of back-to-back diode pairs, each pair in parallel with many other pairs. When a relatively small voltage is applied across the electrodes of the MOV, a relatively smaller current flows caused by reverse leakage through the diode junctions. In contrast, when a relatively larger voltage is applied, the diode junction breaks down due to a combination of thermionic emission and electron tunneling, resulting in a relatively larger current flow.

The result of this behavior is a nonlinear current-voltage characteristic, in which the MOV has a high resistance at low voltages and a low resistance at high voltages. However, in an HV surge event or abnormal overload condition (e.g., an overvoltage condition) above a voltage range that the MOV may physically tolerate without damage, the ceramic mass of zinc oxide grains in the matrix of other metal oxides may heat up, chemically react, sublimate, evaporate, and/or otherwise degrade to the point where the chemicals are catastrophically ejected from the packaging of the MOV. Throughout the description, this damage to the MOV and subsequent ejection of material may be referred to as “chemical ejection.” These ejected chemicals may cause damage to other electrical devices within the utility meter. In some instances, the ejected chemicals may include ionized plasma that may damage surrounding components of the utility meter through electrical shorting. Further, the ionized plasma may even cause portions of the utility meter to heat up and burn, which may, in turn, result in fire damage to the utility meter and/or the structure to which the utility meter is coupled. Thus, in the examples described herein, mechanical structures may be included in the utility meter surrounding the MOV and/or other devices to provide for venting of the chemical ejection to occur into a region of the utility meter that does not include high voltage clearances and away from portions of the utility meter that include flammable materials.

In the examples described herein, the high-voltage protection module (e.g., circuitry) and the mechanical structures allow for the utility meter to fail gracefully under HV surge events and abnormal overload conditions such as a sustained overvoltage condition that may occur on the power grid. To fail gracefully may include the containment of any electrical short, outgassing, chemical ejections, etc., without damaging a remaining portion of the utility meter and its electrical and mechanical components and/or the structure to which the utility meter is coupled.

Overview

In the examples described herein, high-voltage protection module for a metrology device is provided to allow the metrology device fails gracefully in the event of an abnormal overvoltage or overcurrent scenario faced during on-field deployment. With a protection circuit, an MOV provides for a clamping voltage that serves to protect the metrology device and its various electrical components from damage by clamping any incoming HV surge or other abnormal overload condition. Further, a fuse and a resistor allow for interruption of sustained overload and/or overvoltage instances while providing effective current through which PLC communications may be possible via a PLC communications frontend and a PLC transceiver. Still further, a first sub-housing provides for containment and control of chemical ejections from the MOV, and thus, prevent the node (e.g., metrology device) from catastrophic failure.

Examples described herein provide a high-voltage protection module for a metrology device including a metal-oxide varistor (MOV) coupled across a mains power line, a resistor electrically coupled to the MOV in series and in front of the MOV, and a fuse electrically coupled to the MOV and the resistor in series, the resistor being located between the fuse and the MOV. The fuse opens upon an overvoltage event disengaging alternating current (AC) power from the mains power line to the metrology device.

The high-voltage protection module further includes a first housing, the first housing enclosing the MOV. The first housing includes a base portion to enclose a first portion of the MOV, and a top portion to enclose a second portion of the MOV, the top portion having an aperture defined therein to vent outgassing. The aperture defined in the top portion is defined in the top portion opposite a first side of the first housing relative to at least one component of the metrology device. The aperture includes a first aperture defined in the top portion, the first aperture venting to a first side of the top portion, and a second aperture defined in the top portion. The second aperture vents to a second side of the top portion opposite the first side.

The high-voltage protection module further includes a second housing. The second housing encloses the fuse and the resistor. The second housing is located on a second side opposite the first side. In one example, the MOV includes a first MOV coupled to the resistor and the fuse in series, and a second MOV coupled to the resistor and the fuse in series.

The high-voltage protection module further includes a power line carrier (PLC) communication frontend electrically coupled in series with the fuse and the resistor in series and in parallel with the MOV. The PLC communication frontend couples the mains power line to a PLC transceiver. The PLC communication frontend includes a capacitor in series with the fuse and the resistor, and a diode to provide clamp protection for the PLC transceiver.

Examples described herein also provide a metrology device including a power line carrier (PLC) transceiver, and a high-voltage protection module. The high-voltage protection module includes a metal-oxide varistor (MOV) coupled over a mains power line, a resistor electrically coupled to the MOV in series, and a fuse electrically coupled to the MOV and the resistor in series. The fuse opens upon an overvoltage event disengaging alternating current (AC) power from the mains power line to the metrology device.

The high-voltage protection module further includes a first housing, the first housing enclosing the MOV. The first housing includes a base portion to enclose a first portion of the MOV, and a top portion to enclose a second portion of the MOV, the top portion having an aperture defined therein to vent outgassing. The aperture defined in the top portion is defined in the top portion opposite a first side of the first housing relative to at least one component of the metrology device.

The high-voltage protection module further comprises a second housing. The second housing encloses the fuse and the resistor. The second housing is located on a second side opposite the first side.

The high-voltage protection module further includes a PLC communication frontend electrically coupled in series with the fuse and the resistor in series and in parallel with the MOV. The PLC communication frontend couples the mains power line to a PLC transceiver. The PLC communication frontend includes a capacitor in series with the fuse and the resistor, and a diode to provide clamp protection for the PLC transceiver.

In one example, the MOV includes a first MOV coupled to the resistor and the fuse in series and a second MOV coupled to the resistor and the fuse in series. The aperture includes a first aperture defined in the top portion, the first aperture venting to a first side of the top portion, and a second aperture defined in the top portion, the second aperture venting to a second side of the top portion opposite the first side.

Examples described herein also provide a network including a metrology device communicatively coupled within the network, and a central office communicatively coupled to the metrology device at least in part over a power line. The metrology device includes a metrology unit. The metrology unit includes a high-voltage protection module including a metal-oxide varistor (MOV) coupled over a mains power line, a resistor electrically coupled to the MOV in series, and a fuse electrically coupled to the MOV and the resistor in series. The fuse opens upon an overvoltage event disengaging alternating current (AC) power from the mains power line to the metrology device.

The metrology device further includes a power line carrier (PLC) transceiver, and a PLC communication frontend electrically coupled in series with the fuse and the resistor in series and electrically coupled in parallel with the MOV. The PLC communication frontend couples the mains power line to the PLC transceiver.

The high-voltage protection module further includes a first housing, the first housing enclosing the MOV. The first housing includes a base portion to enclose a first portion of the MOV, and a top portion to enclose a second portion of the MOV, the top portion having an aperture defined therein to vent outgassing. The aperture defined in the top portion is defined in the top portion opposite a first side of the first housing relative to at least one component of the metrology device. The high-voltage protection module further includes a second housing. The second housing encloses the fuse and the resistor. The second housing is located on a second side opposite the first side.

The PLC communication frontend includes a capacitor in series with the fuse and the resistor, and a diode to provide clamp protection for the PLC transceiver. The MOV includes a first MOV coupled to the resistor and the fuse in series and a second MOV coupled to the resistor and the fuse in series.

The aperture includes a first aperture defined in the top portion. The first aperture vents to a third side of the top portion. The aperture includes a second aperture defined in the top portion. The second aperture vents to a fourth side of the top portion opposite the third side.

Additionally, the techniques described in this disclosure may be performed as a method and/or by a system having non-transitory computer-readable media storing computer-executable instructions that, when executed by one or more processors, performs the techniques described above.

Example Embodiments

Turning now to the figures,FIG.1is a diagram showing a high-level view of a network architecture100including nodes106configured with a high-voltage protection module, according to an example of the principles described herein. As used herein and in the appended claims, the high-voltage protection module includes electrical circuitry and/or mechanical structures that allow for the utility meter to fail gracefully under HV surge events and abnormal overload conditions such as a sustained overvoltage condition that may occur on the power grid.FIG.1also includes a component diagram of example components of a node106that includes the high-voltage protection module. The network architecture100includes a plurality of node(s)106-1,106-2,106-3,106-4,106-5,106-6,106-7, . . . ,106-N, whereNis any integer greater than or equal to 1 (collectively referred to herein as node(s)106unless specifically addressed otherwise). The nodes106are communicatively coupled to each other via direct communication paths or “links.” In this example, N represents a number of nodes in an autonomous routing area (ARA), such as a wide area network (WAN), metropolitan area network (MAN), local area network (LAN), neighborhood area network (NAN), field area network (FAN), personal area network (PAN), among other types of networks. As an example, the nodes106may be configured in an RF mesh, a PLC mesh, or both. In one example, nodes106may be part of a low power and lossy network (LLN). The nodes106are or include utility meters used to measure an amount of the utility such as electricity, water, and gas consumed by a residence, a commercial building, or an electrically powered device.

As used in the present specification and in the appended claims, the term “link” is meant to be understood broadly as any direct communication path between two nodes (e.g., a “one hop” transmission that does not pass through or become propagated by another node). Each link may represent a plurality of channels or one or more variable data rate channels over which a node106is able to transmit or receive data. Each link may include multiple communication technologies, such as, for example, one or more PLC communication technologies.

One or more channels may use a power line communication (PLC) system communicated using a PLC communications technology. Thus, a link may include portions based on multiple communication medias including PLC portions. Likewise, various links may use multiple different PLC communications technologies (e.g., various modulation techniques, bandwidths, data rates, center frequencies, protocols, etc.).

The channels on a link may include a control channel and multiple data channels. In some instances, the control channel is utilized for communicating one or more messages between nodes to specify one of the data channels to be utilized to transfer data. In one example, transmissions on the control channel may be shorter relative to transmissions on the data channels. Once specified, the nodes may move to the data channel for communication.

Each of the nodes106may be implemented as, or associated with, any of a variety of computing devices such as, for example, smart utility meters (e.g., electric, gas, and/or water meters), sensors (e.g., temperature sensors, weather stations, frequency sensors, etc.), control devices, transformers, routers, servers, relays (e.g., cellular relays), switches, valves, power line communication (PLC) transceivers, combinations of the foregoing, or any device couplable to a communication network and capable of sending and/or receiving data.

In this example, the nodes106may also be configured to communicate with one or more central processing facilities such as a central office102via an edge device (e.g., cellular relay, cellular router, edge router, destination oriented directed acyclic graph (DODAG) root, etc.) which serves as a connection point of the ARA to a backhaul network(s)104, such as the Internet or one or more public or private intranets. In the illustrated example, node106-1and/or node106-5may serve as edge devices and/or cellular relays to relay communications from the other nodes106-2through106-Nof the ARA to and from the central office102via the network(s)104.

As an example, node106-Nmay be representative of each of the nodes106and includes a radio (e.g., a transceiver)108, a PLC transceiver110and a processing unit112. The radio108may include a radio frequency (RF) transceiver that may be configured to receive RF signals associated with multiple different RF communication technologies (e.g., FSK, OQPSK, OFDM, CDMA, etc.) at a variety of data rates, and transmit RF signals via one or more of a plurality of RF communication technologies. The radio108may include a multiple protocol receiver and may be configured to listen for a plurality of different RF communication technologies in a parallel fashion across multiple links. The radio108may also be configured to determine, or facilitate determination of, a received signal strength, such as a “received signal indicator” (RSI) for one or more of the plurality of different RF communication technologies.

In some implementations, each of the nodes106includes a single radio108configured to send and receive data on multiple different channels, such as the control channel and multiple data channels of each communication link. The radio108may also be configured to implement a plurality of different data rates, protocols, signal strengths, and/or power levels. The network architecture100may represent a heterogeneous network of nodes106, in that the nodes106may include different types of nodes (e.g., smart meters, cellular relays, sensors, etc.), different generations or models of nodes, and/or nodes that otherwise are capable of transmitting on different channels and using different communication technologies, data rates, protocols, signal strengths, and/or power levels.

The power line communication (PLC) transceiver110is configured to transmit and/or receive one or more communication signals on electrical power wiring, including local power wiring and long distance high voltage transmission lines. The PLC transceiver110may transmit and/or receive different types of power line communications that include one or more PLC communication technologies (e.g., narrowband PLC, broadband PLC, power line digital subscriber line (PDSL), power line telecom (PLT), power line networking (PLN), broadband over power lines (BPL), etc.) having one or more frequency bands, channels, data rates and/or types of modulation that may depend on the propagation characteristics of the power wiring used.

The processing unit112is coupled to radio108and PLC transceiver110, and may include one or more processor(s)114communicatively coupled to memory116. The processor(s)114may include one or more cores. Further, the node106-Nmay include one or more network interfaces configured to provide communications between the nodes106, the central office102, and other devices. The network interfaces may include devices configured to couple to personal area networks (PANs), wired and wireless local area networks (LANs), wired and wireless wide area networks (WANs), and so forth. For example, the network interfaces may include devices compatible with the nodes106, the central office102, and other devices.

The memory116may be configured to store one or more software and/or firmware modules, which are executable on the processor(s)114to implement various functions as described herein. While the modules118are described herein as being software and/or firmware executable on a processor, in other embodiments, any or all of the modules may be implemented in whole or in part by hardware (e.g., as an ASIC, a specialized processing unit, digital signal processor, etc.) to execute the described functions. The memory116may store various executable components (e.g., software-based components, firmware-based components, etc.) as the modules118. In addition to various components discussed herein, the memory116may further store components to implement functionality described herein. While not illustrated, the memory116may store one or more operating systems utilized to control the operation of the one or more devices that include the node106-N. According to one example, the operating system includes the LINUX operating system. According to another example, the operating system(s) include the WINDOWS SERVER operating system from MICROSOFT Corporation of Redmond, Wash. According to further examples, the operating system(s) may include the UNIX operating system or one of its variants. It may be appreciated that other operating systems may also be utilized.

The memory116may include computer-readable media and may take the form of volatile memory, such as random access memory (RAM) and/or non-volatile memory, such as read only memory (ROM) or flash RAM. Computer-readable media includes volatile and non-volatile, removable, and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules, or other data for execution by one or more processors of a computing device. Examples of computer-readable media include, but are not limited to, phase change memory (PRAM), static random-access memory (SRAM), dynamic random-access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information for access by a computing device. As defined herein, computer-readable media does not include communication media, such as modulated data signals and carrier waves.

The network(s)104may represent a backhaul network, which may itself include a wireless or a wired network, or a combination thereof. The network(s)104may be a collection of individual networks interconnected with each other and functioning as a single large network (e.g., the Internet and/or one or more intranets). Further, the individual networks may be wireless or wired networks, or a combination thereof.

The central office102may be implemented by one or more computing devices, such as servers, personal computers, laptop computers, etc. The one or more computing devices may be equipped with one or more processor(s) communicatively coupled to memory. In one example, the central office102includes a centralized meter data management system which performs processing, analysis, storage, and/or management of data received from one or more of the nodes106. For example, the central office102may process, analyze, store, and/or manage data obtained from a smart utility meter, sensor, control device, router, regulator, server, relay, switch, valve, and/or other nodes. Although the example ofFIG.1illustrates the central office102in a single location, in some examples the central office may be distributed amongst multiple locations and/or may be eliminated entirely (e.g., in the case of a highly decentralized distributed computing platform).

Electrical power may be measured by a metrology unit120associated with one or more of the nodes106-Nas the power is used by a consumer. In one example, power is delivered to a consumer from a transformer (not shown) by an electrical conductor132. The quantity of power that is delivered is measured by the metrology unit120associated with node106-N. The metrology unit120associated with node106-Nis able to detect, measure, interrupt, and protect the node106-Nfrom the power delivered over the conductor132. The electrical power measured by the metrology unit120may be transmitted to the central office102, and the central office102may be configured to include collection engine (CE) functionality. In one example, aspects of the CE functionality may be distributed, partly or fully, within some or all of the nodes106. The central office102and its functionality may be centralized within a utility company, distributed among locations within the network104, and/or located in a data center location or “cloud” environment.

The metrology unit120may be communicatively coupled to the radio108, the PLC transceiver110, and the procession unit112, among other devices described herein in order to process and transmit detected electrical power measurements to other nodes106and/or the central office102.

In the examples described herein, the metrology unit102may include a metal-oxide varistor(s) (MOVs)124, resistor(s)126, and fuse(s)128. The MOV(s)124, resistor(s)126, and fuse(s)128may be housed in sub-housing(s)122as described herein to avoid catastrophic failure of the metrology unit120including other elements of the metrology unit120such as processing elements, circuitry, printed circuit boards (PCBs), etc. As described above, an HV surge event and/or an abnormal overload condition may cause circuitry elements including the MOV(s)124, resistor(s)126, and fuse(s)128to chemically react, sublimate, evaporate, and/or otherwise degrade to the point where the chemicals are catastrophically ejected from the packaging of the MOV(s)124, resistor(s)126, and/or fuse(s)128. In order to allow the node106-Nand the metrology unit120to fail gracefully without damaging other elements of the node106-N, the sub-housing(s)122may include apertures and other architectures that cause chemical ejection to be directed away from those elements within the metrology unit102and/or the node106-N(e.g., the utility meter). The specific circuitry and sub-housing122architectures are described in more detail below.

The node106-Nmay further include a PLC communication frontend130. The PLC communication frontend130provides for communications to be sent via the architecture100of the network(s)104as a frontend device of the PLC transceiver110. The PLC communication frontend130causes the PLC communication signals obtained via the PLC communication links between the nodes106, the network104, and the central office102. The PLC communication frontend130is a sub-circuit within the high-voltage protection module that serves as an intermediary between the network of nodes106and the PLC transceiver110.

The MOV(s)124include any varistor including, for example, a metal-oxide varistor as denoted by the acronym MOV. The MOV124within the utility meter (e.g., node106-N) may be placed directly across the mains line in order to reduce clamping voltage (e.g., a let-through voltage). The clamping voltage defines what spike voltage may cause the protective components such as the MOV to short or “clamp.” The MOV124, therefore, is able to clamp any incoming HV surge or abnormal overload condition. A relatively lower clamping voltage provides relatively better protection but may result in a shorter life expectancy for the overall protective system. In a first approach, a circuit including an MOV within a utility meter may be designed such that energy into the MOV124is limited. This first approach assumes the MOV124will short (e.g., fail) during its lifetime. This approach may result in increased costs of replacing the MOV124itself as well as downtime for the utility meter and time spent by a service technician to replace the MOV124. The second approach may include designing the MOV itself such that it will not short (e.g., fail) in the first instance throughout the life of the utility meter. This second approach includes an MOV124that is over-spec'd to increase the robustness of the MOV124. However, as mentioned above, some regulatory and product safety organizations as well as consumers of metrology devices have determined that a wear out mechanism within the MOV124will result in even a relatively more robust MOV124ultimately shorting or failing.

Thus, the present systems and methods seek to address these issues based on the first approach. Further, as mentioned above, having the MOV124located directly across an electrical line may be considered by the regulatory and product safety organizations and consumers of metrology devices as a design point that may not be tolerated. As will be described in more detail below in connection withFIG.2, a high-voltage protection module used to protect the metrology unit120from an HV surge event and/or an abnormal overload condition may also include the fuse(s)128and the resistor(s)126in series with the MOV124in order to protect from these overvoltage situations that would cause the MOV124to fail short. In one example, a series limiting resistor126is included within the circuit associated with the MOV124to allow the fuse128to break currents with service voltages that would normally exceed the rating of the fuse128. In one example of a simulated overload and/or overvoltage condition that the protection circuit (FIG.2,200) may be exposed to may include an abnormal overvoltage scenario of, for example, a 3,000 VAC that rapidly diminishes the voltage clamping capability of the MOV124. In this scenario, the fuse128is able to open in approximately 3.5 cycles and disengage the mains power to the node106-N, and the PLC communication frontend130. In this manner, the fuse128limits the exposure to an overload and/or overvoltage condition that may lead to the node106-N(e.g., the utility meter) failing catastrophically.

Inclusion of a series limiting resistor126in front of the fuse128may not be necessary in most situations since most applications utilize entirely low ohmic connection for efficiency or power demand. Communication modules such as the PLC transceiver110and the associated PLC communication frontend130do not draw significant amounts of power, so these communication modules can tolerate some level of impedance. PLC communication devices such as the PLC transceiver110and the associated PLC communication frontend130require a direct connection to mains power, and because this direct connection to the mains power exists, the mains power must be protected. Further, because the components of the node106-Nrequire certain physical clearance reductions, the MOV124is located directly across an electrical line. Here, physical clearance may be defined as empty space along a plane such as a printed circuit board or other substrate on which electrical components are coupled. At the same time, if a fusible resistor (e.g., the resistor126and fuse128in series) is placed in front of the MOV124in order to protect the mains power, a sufficiently large resistor126may be required. However, placing such a large resistor126in front of the MOV124may cause the PLC communications abilities of the PLC transceiver110and the associated PLC communication frontend130to become severely attenuated or diminished. Thus, several constraints may be balanced including protecting the MOV124via the resistor126and fuse128in series with the MOV124in a condition in which it shorts or fails while providing a sufficiently effective PLC communication path for the PLC transceiver110and the associated PLC communication frontend130.

Thus, in the examples described herein, a sufficiently robust MOV124is included in the high-voltage protection module of the metrology device (e.g., the node106-N), including the fuse128in series with the MOV124in case the MOV124fails short (causing the fuse128to open). The fuse128by itself in series with the MOV124, however, may not be able to break the current to the MOV124fast enough to prevent the MOV124from failing and expelling chemicals into the enclosure of the node106-Nunless the fuse128was a relatively fast-blow grade fuse. Such a relatively fast-blow grade fuse may not be sufficient to adhere to one or more product safety requirements related to surge withstand capability. In other words, use of a relatively fast-blow grade fuse may result in nuisance failures in the field where the node106-Nis located requiring an expensive and technical service and replacement process to replace the fuse128and increases the chance that a service technician may injure themselves while working on a high voltage system such as the node106-N. Thus, the inclusion of the resistor126in series with and between the MOV124and the fuse128limits the current the fuse128would have to break in an HV surge event and/or an abnormal overload condition (the fuse rated at, for example, 10 kiloamps (kA)) as well as limits the voltage and allows the fuse128to break while still providing surge capabilities. Selection of the components to ensure compliance in a metering environment may be emphasized in order to take into consideration that a specific resistor126or fuse128function within the high-voltage protection module described herein in order to control the failure chain.

As described above, the high-voltage protection module including the fuse128and resistor126in series with the MOV124allows for the MOV124to be used across the electrical line, the resistor126allows for the use of a robust fuse128, and the resistor126and fuse128allow for maintaining efficient PLC communication via the PLC transceiver110and the associated PLC communication frontend130. However, the MOV124may still, in some instances, short or fail potentially resulting in chemical ejection. Thus, the sub-housing(s)122described herein provide a mechanical means of ensuring the chemical ejection is directed away from other elements of the node106-N. The mechanical means used to direct chemical ejection away from the other elements of the node106-Nis described in connection withFIGS.3through5.

FIG.2illustrates a protection circuit200of the high-voltage protection module ofFIG.1, according to an example of the principles described herein. As mentioned above, the high-voltage protection module includes at least the MOV124, the resistor126, and the fuse128(along with the mechanical architecture described in connection withFIGS.3through5). As depicted inFIG.2, a mains power line enters the protection circuit200as indicated by VA. Current flows through the fuse128and the resistor126and branches into two separate directions to the MOV124and separately to the PLC communication frontend130. As noted above, the current flowing through the fuse128and the resistor126provides for maintaining efficient PLC communication between the nodes106, the network104, and the central office102. The fusible resistor (e.g., the fuse128in series with the resistor126) is placed in front of the MOV124such that an HV surge event or other abnormal overload condition will cause the fusible resistor to open, and, in turn, protect the remainder of the circuit and the overall utility meter.

The PLC communication frontend130may include a capacitor134in series with the fuse128and resistor126. The capacitor134may be, for example, a 0.22 microfarad (μF) capacitor. The PLC communication frontend130may also include a diode136. The diode136may provide, for example, a 5V clamp protection to the PLC transceiver110to which the PLC communication frontend130is electrically coupled as indicated by the PLC transformer (e.g., “PLC XFMR”). In one example, PLC XFMR may include a transformer located on a register board of the PLC transceiver110. The diode136is also electrically coupled to ground. Thus, the low-voltage signal provided to the PLC transceiver110via the PLC communication frontend130is protected primarily by the MOV124and secondarily by the diode136. The diode136is also electrically coupled to ground. In one example, the diode136may include a transient voltage suppression (TVS) diode configured to protect the PLC transceiver110via the PLC communication frontend130from voltage spikes that may occur as described herein.

The current from the power grid also flows through the fuse128and the resistor126and on to the MOV124. The MOV124may include any voltage-dependent resistor (VDR). MOVs may be specified according to the voltage range that they can tolerate without damage, the varistor's energy rating in joules, operating voltage, response time, maximum current, and breakdown (clamping) voltage. In one example, the MOV124may have a clamping voltage of 2.2 kilovolt (kV). The clamping voltage is the voltage the MOV124will limit the protection circuit200to when the MOV124sees an overload condition. Surge voltages up to the clamp voltage will be allowed, but the MOV124will begin to shunt current around the MOV124rating, progressively, up to the clamp voltage. At the clamp voltage, the resistance of the MOV124is as low as may be reasonable in a particular application. Stated another way, the clamp voltage represents a point at which the resistance of the MOV124is at a minimum such that any excess energy begins to be dumped progressively as more current is present. Further, current from the mains power may flow to other elements of the node106such as, for example, a rectifier bridge and an AC/DC supply as indicated inFIG.2. The MOV124is also electrically coupled to ground.

As described above, the utility meter (e.g., node106-N) is subjected to HV surges directly connected to the power grid. The MOV124assists in protecting the utility meter and its various electrical components from damage due to the HV surges by clamping any incoming HV surge or other abnormal overload condition. The MOV protects excessive transient voltages within the utility meter and shunts the current created by an excessive voltage away from sensitive components when triggered.

The high-voltage protection module (e.g., circuitry) depicted inFIG.2, along with the mechanical structures depicted and described in connection withFIGS.3through6allow for the utility meter to fail gracefully under HV surge events and abnormal overload conditions such as a sustained overvoltage condition that may occur on the power grid. Thus, turning now toFIGS.3through5,FIGS.3through5illustrate a schematic diagram of the high-voltage protection module ofFIG.1, according to an example of the principles described herein. As depicted inFIGS.3through5, various components of the utility meter (e.g., node106-N) may be mechanically and/or electrically coupled to a printed circuit board (PCB)306. For example, the fuse128, the resistor126, and the MOV124may be electrically coupled to the PCB306.

Further, the node106-Nmay include a first sub-housing122-1and a second sub-housing122-2. Elements122-1and122-2are referred to herein as sub-housings because the node106-Nmay include a housing that encloses the components of the node106-Nincluding all the components depicted inFIGS.2through6. However, the first sub-housing122-1and the second sub-housing122-2may also be referred to as housings in their own right. The first sub-housing122-1and the second sub-housing122-2may be made of any material including plastics. In one example, the first sub-housing122-1and the second sub-housing122-2may be made of a metal, metal alloy, a ceramic, or other material. In one example, the first sub-housing122-1and the second sub-housing122-2may be made of a fire resistant or fire retardant material.

The first sub-housing122-1may enclose the MOV124in order to physically isolate the MOV124from other components of the node106-N. The MOV124is physically isolated to protect the remainder of the components of the node106-Nin instances where the MOV124is subjected to an HV surge event such as a sustained overvoltage condition that may result in chemical ejection from the MOV124(e.g., ejection of ionized plasma that may damage surrounding components of the utility meter). More regarding the manner in which the chemical ejection of the MOV124may take place is described below.

The second sub-housing122-2may enclose the fuse128and the resistor126in order to isolate the fuse128and the resistor126in a manner similar to how the MOV124is isolated within the first sub-housing122-1. In some instances of the HV surge events, the fuse128may open to provide overcurrent protection of the high-voltage protection module and stopping or interrupting the current. The fuse128and/or the resistor126may also, like the MOV124, suffer from a chemical ejection instance, and, therefore, the sub-housing122-2also helps to protect the remainder of the components of the node106-N.

Turning again to the first sub-housing122-1, the first sub-housing122-1may include a bottom portion302to secure the MOV124to the PCB306and contain the MOV124. In one example the bottom portion302encloses the MOV124on five sides leaving the MOV124open at the top as depicted inFIG.3. The first sub-housing122-1may also include a top portion402that covers the MOV124on at least one side. As depicted inFIGS.3through5, the top portion402may cover the bottom portion302and the MOV124on five sides of the bottom portion302and the MOV124such that the bottom portion302nests inside the top portion402. In this manner, the bottom portion302and the top portion402enclose the MOV124on at least 6 sides of the MOV124.

In one example, the bottom portion302may include a first notch304defined at a top of the bottom portion302, and the top portion304may include a second notch404defined at a top of the top portion402. As depicted in, for example,FIGS.4and5, the first notch304and the second notch404line up with one another such that the MOV124is exposed via the first notch304and the second notch404via an aperture406defined by the first notch304and the second notch404. The aperture406(defined by the first notch304and the second notch404) is located on a side of the bottom portion302and the top portion402that is opposite a side of the first housing122-1that includes at least one component of the node106-Nincluding the fuse128, the resistor126, the PCB306and other electrical components coupled thereto, and other components of the node106-N. The aperture406creates a pathway from which chemical ejections from the MOV124may be expelled away from these components in order to ensure that the node106-Nmay gracefully fail without causing additional damage to the remainder of the node106-Nincluding its components and without causing damage to the structure such as a residence or commercial property to which the node106-Nis coupled. In other words, in instances where an HV surge event or abnormal overload condition (e.g., an overvoltage condition) is present and the MOV124physically breaks down and begins a chemical ejection, those dangerous chemicals including ionized plasma may be ejected out of the first housing122-1via the aperture406and away from susceptible components of the node106-N.

With reference toFIGS.2through5, in one example, the high-voltage protection module may include a plurality of MOVs124, fuses128, and resistors126within the circuit depicted inFIG.2and corresponding layouts inFIGS.3through5. In this example, a first MOV124may be electrically coupled to a first fuse128and a first resistor126in series, and separately, a second MOV124may be electrically coupled to a second fuse128and a second resistor126in series separate. This creates two separate protection circuits that are electrically coupled to the mains power. In one example, a first MOV and a second MOV may be coupled to the same fuse128and resistor126with each of the first MOV and second MOV being in series with the fuse128and resistor126.

In these examples of multiple MOVs124and/or fuses128and resistors126, the first housing122-1may be configured to contain two separate MOVs and the aperture406defined in the bottom portion302and the top portion402may include two or more apertures406. The two or more apertures may be formed on separate sides adjacent to the side the aperture406is formed as depicted inFIGS.3through5. Any chemical ejections emitted via the apertures in this example may be ejected at those adjacent sides. In another example, two separate apertures may be formed on the same side as the side the aperture406is formed as depicted inFIGS.3through5. Further, in the above examples of multiple MOVs124and/or fuses128and resistors126, the multiple fuses128and resistors126may be contained within the same or a different second sub-housing122-2.

With the circuit depicted inFIG.2, the MOV124provides for a clamping voltage that serves to protect the utility meter and its various electrical components from damage by clamping any incoming HV surge or other abnormal overload condition fuse128and resistor126. Further, the fuse128and resistor126allow for interruption of sustained overload and/or overvoltage instances while providing effective current through which PLC communications may be possible via the PLC communications frontend130and the PLC transceiver110. Still further, the first sub-housing122-1provides for containment and control of chemical ejections from the MOV124, and thus, prevent the node106-N(e.g., utility meter) from catastrophic failure.

FIG.6illustrates a computing system diagram illustrating a configuration for a data center600that may be utilized to implement aspects of the technologies disclosed herein. The example data center600shown inFIG.6includes several server computers602A-602F (which might be referred to herein singularly as “a server computer602” or in the plural as “the server computers602”) for providing computing resources. In some examples, the resources and/or server computers602may include, or correspond to, any type of networked device described herein including the nodes106and any computing device associated with the central office102. Although described as servers, the server computers602may comprise any type of networked device, such as servers, switches, routers, hubs, bridges, gateways, modems, repeaters, access points, utility meters, workstations, desktop computers, laptop computers, tablet computing devices, network appliances, e-readers, smartphones, or other computing device etc.

The server computers602may be standard tower, rack-mount, or blade server computers configured appropriately for providing computing resources. In some examples, the server computers602may provide computing resources604including data processing resources such as VM instances or hardware computing systems, database clusters, computing clusters, storage clusters, data storage resources, database resources, networking resources, virtual private networks (VPNs), and others. Some of the server computers602may also be configured to execute a resource manager606A-606F capable of instantiating and/or managing the computing resources. In the case of VM instances, for example, the resource manager606A-606F may be a hypervisor or another type of program configured to enable the execution of multiple VM instances on a single server computer602. Server computers602in the data center600may also be configured to provide network services and other types of services.

In the example data center600shown inFIG.6, an appropriate LAN608is also utilized to interconnect the server computers602A-602F. It may be appreciated that the configuration and network topology described herein has been greatly simplified and that many more computing systems, software components, networks, and networking devices may be utilized to interconnect the various computing systems disclosed herein and to provide the functionality described above. Appropriate load balancing devices or other types of network infrastructure components may also be utilized for balancing a load between data centers600, between each of the server computers602A-602F in each data center600, and, potentially, between computing resources in each of the server computers602. It may be appreciated that the configuration of the data center600described with reference toFIG.6is merely illustrative and that other implementations may be utilized.

In some examples, the server computers602and or the computing resources604may each execute/host one or more tenant containers and/or virtual machines to perform techniques described herein.

In some instances, the data center600may provide computing resources, like tenant containers, VM instances, VPN instances, and storage, on a permanent or an as-needed basis. Among other types of functionality, the computing resources provided by a cloud computing network may be utilized to implement the various services and techniques described above. The computing resources604provided by the cloud computing network may include various types of computing resources, such as data processing resources like tenant containers and VM instances, data storage resources, networking resources, data communication resources, network services, VPN instances, and the like.

Each type of computing resource604provided by the cloud computing network may be general-purpose or may be available in a number of specific configurations. For example, data processing resources may be available as physical computers or VM instances in a number of different configurations. The VM instances may be configured to execute applications, including web servers, application servers, media servers, database servers, some or all of the network services described above, and/or other types of programs. Data storage resources may include file storage devices, block storage devices, and the like. The cloud computing network may also be configured to provide other types of computing resources604not mentioned specifically herein.

The computing resources604provided by a cloud computing network may be enabled in one example by one or more data centers600(which might be referred to herein singularly as “a data center600” or in the plural as “the data centers600”). The data centers600are facilities utilized to house and operate computer systems and associated components. The data centers600may include redundant and backup power, communications, cooling, and security systems. The data centers600may also be located in geographically disparate locations. One illustrative example for a data center600that may be utilized to implement the technologies disclosed herein is described herein with regard to, for example,FIGS.1through5.

FIG.7illustrates a computer architecture diagram showing an example computer hardware architecture700for implementing a computing device that may be utilized to implement aspects of the various technologies presented herein. The computer hardware architecture700shown inFIG.7illustrates the nodes106, computing devices located at the central office102, and/or other systems or devices associated with the nodes106and/or remote from the nodes106, a utility meter, a workstation, a desktop computer, a laptop, a tablet, a network appliance, an e-reader, a smartphone, or other computing device, and may be utilized to execute any of the software and/or hardware components presented herein. The computer700may, in some examples, correspond to a network device (e.g., the nodes106) described herein, and may include networked devices such as servers, switches, routers, hubs, bridges, gateways, modems, repeaters, access points, etc.

The computer700includes a baseboard702, or “motherboard,” which is a printed circuit board (e.g., the PCB306ofFIG.3) to which a multitude of components or devices may be connected by way of a system bus or other electrical communication paths. In one illustrative configuration, one or more central processing units (CPUs)704operate in conjunction with a chipset706. The CPUs704may be standard programmable processors that perform arithmetic and logical operations necessary for the operation of the computer700.

The chipset706provides an interface between the CPUs704and the remainder of the components and devices on the baseboard702. The chipset706may provide an interface to a RAM708, used as the main memory in the computer700. The chipset706may further provide an interface to a computer-readable storage medium such as a read-only memory (ROM)710or non-volatile RAM (NVRAM) for storing basic routines that help to startup the computer700and to transfer information between the various components and devices. The ROM710or NVRAM may also store other software components necessary for the operation of the computer700in accordance with the configurations described herein.

The computer700may operate in a networked environment using logical connections to remote computing devices and computer systems through a network, such as the nodes106, the network104, and the central office102. The chipset706may include functionality for providing network connectivity through a Network Interface Controller (NIC)712, such as a gigabit Ethernet adapter. The NIC712is capable of connecting the computer700to other computing devices within the network architecture100and external to the network architecture100. It may be appreciated that multiple NICs712may be present in the computer700, connecting the computer to other types of networks and remote computer systems. In some examples, the NIC712may be configured to perform at least some of the techniques described herein, such as packet redirects and/or other techniques described herein.

The computer700may be connected to a storage device718that provides non-volatile storage for the computer. The storage device718may store an operating system720, programs722, and data, which have been described in greater detail herein. The storage device718may be connected to the computer700through a storage controller714connected to the chipset706. The storage device718may consist of one or more physical storage units. The storage controller714may interface with the physical storage units through a serial attached SCSI (SAS) interface, a serial advanced technology attachment (SATA) interface, a fiber channel (FC) interface, or other type of interface for physically connecting and transferring data between computers and physical storage units.

In addition to the storage device718described above, the computer700may have access to other computer-readable storage media to store and retrieve information, such as program modules, data structures, or other data. It may be appreciated by those skilled in the art that computer-readable storage media is any available media that provides for the non-transitory storage of data and that may be accessed by the computer700. In some examples, the operations performed by the nodes106and or any components included therein, may be supported by one or more devices similar to computer700. Stated otherwise, some or all of the operations performed by the node106, and or any components included therein, may be performed by one or more computer devices operating in a cloud-based arrangement.

By way of example, and not limitation, computer-readable storage media may include volatile and non-volatile, removable, and non-removable media implemented in any method or technology. Computer-readable storage media includes, but is not limited to, RAM, ROM, erasable programmable ROM (EPROM), electrically-erasable programmable ROM (EEPROM), flash memory or other solid-state memory technology, compact disc ROM (CD-ROM), digital versatile disk (DVD), high definition DVD (HD-DVD), BLU-RAY, or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that may be used to store the desired information in a non-transitory fashion.

As mentioned briefly above, the storage device718may store an operating system720utilized to control the operation of the computer700. According to one example, the operating system720includes the LINUX operating system. According to another example, the operating system includes the WINDOWS® SERVER operating system from MICROSOFT Corporation of Redmond, Wash. According to further examples, the operating system may include the UNIX operating system or one of its variants. It may be appreciated that other operating systems may also be utilized. The storage device718may store other system or application programs and data utilized by the computer700.

In one example, the storage device718or other computer-readable storage media is encoded with computer-executable instructions which, when loaded into the computer700, transform the computer from a general-purpose computing system into a special-purpose computer capable of implementing the examples described herein. These computer-executable instructions transform the computer700by specifying how the CPUs704transition between states, as described above. According to one example, the computer700has access to computer-readable storage media storing computer-executable instructions which, when executed by the computer700, perform the various processes described above with regard toFIGS.1-6. The computer700may also include computer-readable storage media having instructions stored thereupon for performing any of the other computer-implemented operations described herein.

The computer700may also include one or more input/output controllers716for receiving and processing input from a number of input devices, such as a keyboard, a mouse, a touchpad, a touch screen, an electronic stylus, or other type of input device. Similarly, an input/output controller716may provide output to a display, such as a computer monitor, a flat-panel display, a digital projector, a printer, or other type of output device. It will be appreciated that the computer700might not include all of the components shown inFIG.7, may include other components that are not explicitly shown inFIG.7, or might utilize an architecture completely different than that shown inFIG.7.

As described herein, the computer700may include one or more of the nodes106, computing devices located at the central office102, and/or other systems or devices associated with the nodes106and/or remote from the nodes106, and/or other systems or devices associated with the nodes106and/or remote from the nodes106. The computer700may include one or more hardware processor(s) such as the CPUs704configured to execute one or more stored instructions. The CPUs704may include one or more cores. Further, the computer700may include one or more network interfaces configured to provide communications between the computer700and other devices, such as the communications described herein as being performed by the nodes106, computing devices located at the central office102, and/or other systems or devices associated with the nodes106and/or remote from the nodes106, and other devices described herein. The network interfaces may include devices configured to couple to personal area networks (PANs), wired and wireless local area networks (LANs), wired and wireless wide area networks (WANs), and so forth. For example, the network interfaces may include devices compatible with Ethernet, Wi-Fi™, and so forth.

The programs722may include any type of programs or processes to perform the techniques described in this disclosure for a node106as described herein. The programs722may enable the devices described herein to perform various operations.

CONCLUSION

The invention makes it possible for electric meters to fail gracefully in the event of an abnormal overvoltage or overcurrent scenario faced during on-field deployment. With the circuit depicted inFIG.2, the MOV124provides for a clamping voltage that serves to protect the utility meter and its various electrical components from damage by clamping any incoming HV surge or other abnormal overload condition. Further, the fuse128and resistor126allow for interruption of sustained overload and/or overvoltage instances while providing effective current through which PLC communications may be possible via the PLC communications frontend130and the PLC transceiver110. Still further, the first sub-housing122-1provides for containment and control of chemical ejections from the MOV124, and thus, prevent the node106-N (e.g., utility meter) from catastrophic failure.

While the present systems and methods are described with respect to the specific examples, it is to be understood that the scope of the present systems and methods are not limited to these specific examples. Since other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, the present systems and methods are not considered limited to the example chosen for purposes of disclosure, and covers all changes and modifications which do not constitute departures from the true spirit and scope of the present systems and methods.

Although the application describes examples having specific structural features and/or methodological acts, it is to be understood that the claims are not necessarily limited to the specific features or acts described. Rather, the specific features and acts are merely illustrative of some examples that fall within the scope of the claims of the application.