ENERGY METERING WITH TEMPERATURE MONITORING
A system for energy metering with temperature monitoring.
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This application claims the benefit of U.S. Provisional App. No. 62/508,732 filed May 19, 2017.
BACKGROUND OF THE INVENTIONThe present invention relates to an energy metering system with temperature monitoring.
The total power consumption of a building or other facility is monitored by the electric utility with a power meter located between the utility's distribution transformer and the facility's power distribution panel. However, in many instances it is desirable to sub-meter or attribute the facility's power usage and cost to different occupancies, buildings, departments, or cost centers within the facility or to monitor the power consumption of individual loads or groups of loads, such as motors, lighting, heating units, cooling units, machinery, etc. These single phase or multi-phase electrical loads are typically connected to one or more of the branch circuits that extend from the facility's power distribution panel. While a power meter may be installed at any location between a load and the distribution panel, it is often advantageous to install a power meter capable of monitoring a plurality of circuits proximate the power distribution panel to provide centralized monitoring of the various loads powered from the panel.
Digital branch current monitors may incorporate data processing systems that can monitor a plurality of circuits and determine a number of parameters related to electricity consumption by the individual branch circuits or groups of circuits. A branch current monitor for measuring electricity consumption by respective branch circuits comprises a plurality of voltage and current transducers that are periodically read by the monitor's data processing unit which, in a typical branch current monitor, comprises one or more microprocessors or digital signal processors (DSP). For example, a branch current monitor from Veris Industries, Inc. enables up to ninety circuits to be monitored with a single meter and utilizes the MODBUS® RTU network communication interface to enable remote monitoring as part of a building or facility management system. The data processing unit periodically reads and stores the outputs of the transducers quantifying the magnitudes of current and voltage samples and, using that data, calculates the current, voltage, power, and other electrical parameters, such as active power, apparent power and reactive power that quantify the distribution and consumption of electricity. The calculated parameters are typically output to a display for immediate viewing or transmitted from the meter's communication interface to another data processing system, such as a building management computer for remote display or further processing, for example formulating instructions to the facility's automated equipment.
The voltage transducers of digital branch current monitors commonly comprise a voltage divider network that is connected to a conductor in which the voltage will be measured. The power distribution panel provides a convenient location for connecting the voltage transducers because typically each phase of the electricity is delivered to the power distribution panel on a separate bus bar and the voltage and phase is the same for all loads attached to the respective bus bar. Interconnection of a voltage transducer and the facility's wiring is facilitated by wiring connections in the power distribution panel, however, the voltage transducer(s) can be connected anywhere in the wiring that connects the supply and a load, including at the load's terminals.
The current transducers of digital power meters typically comprise current transformers that encircle each of the power cables that connect each branch circuit to the bus bar(s) of the distribution panel. Bowman et al., U.S. Pat. No. 6,937,003 B2, discloses a branch current monitoring system that includes a plurality of current transformers mounted on a common support facilitating installation of a branch current monitor in a power distribution panel. Installation of current transformers in electrical distribution panels is simplified by including a plurality of current transformers on a single supporting strip which can be mounted adjacent to the lines of circuit breakers in the panel. The aforementioned branch current monitor from Veris Industries, Inc. is commonly used to monitor up to four strips of current sensors; each comprising 21 current transformers on a common support. In addition, the branch current monitor provides for eight auxiliary current transformer inputs for sensing the current flow in two 3-phase mains with two neutrals and six voltage connections enabling voltage sensing in six bus bars of two 3-phase mains.
Referring in detail to the drawings where similar parts are identified by like reference numerals, and, more particularly to
The voltage module 26 includes one or more voltage transducers 42 each typically comprising a resistor network, a voltage sampling unit 48 to sample the output of the voltage transducers and convert the analog measurements to digital data suitable for use by the data processing unit and a multiplexer 44 that periodically connects the voltage sampling unit to selected ones of the voltage transducers enabling periodic sampling of the magnitude of the voltage at each of the voltage transducers. Typically, each phase of the electricity supplied to a distribution panel is connected to a bus bar 23 to which are connected the circuit breakers 16 that provide a conductive interconnection to each of the respective loads, by way of examples, a single-phase load 21A and a three-phase load 21B. Since the voltage and phase supplied to all commonly connected loads is the same, a meter for measuring three-phase power typically includes three voltage transducers 42A, 42B, 42C each connected to a respective bus bar 23A, 23B, 23C. A clock 40, which may be included in the data processing unit, provides periodic timing signals to trigger sampling of the outputs of the voltage transducers by the voltage sampling unit. The voltage module may also include a voltage sensor memory 46 in which voltage sensor characterization data, including relevant specifications and error correction data for the voltage transducers are stored. If a portion of the voltage module requires replacement, a new voltage module comprising a voltage sensor memory containing sensor characterization data for the transducers of the new module can be connected to the data processing unit. The data processing unit reads the data contained in the voltage sensor memory and applies the sensor characterization data when calculating the voltage from the transducer data output by the replacement voltage module.
The current module 24 typically comprises a current sampling unit 50, a multiplexer 52 and a plurality of current transducers 54 communicatively connected to respective sensor positions 55 of the current module. The multiplexer 52 sequentially connects the sampling unit to the respective sensor positions enabling the sampling unit to periodically sample the output of each of the current transducers 54. The current sampling unit comprises an analog-to-digital converter to convert the analog sample at the output of a current transducer selected by the multiplexer, to a digital signal for acquisition by the data processing unit. The clock 40 also provides the periodic timing signal that triggers sampling of the current transducer outputs by the current sampling unit. The current module may also include a current sensor memory 56 in which are stored characterization data for the current transducers comprising the module. The characterization data may include transducer identities; relevant specifications, such as turns ratio; and error correction factors, for examples equations or tables enabling the phase and ratio errors to be related to a current permitting correction for magnetization induced errors. The characterization data may also include the type of transducers, the number of transducers, the arrangement of transducers and the order of the transducers' attachment to the respective sensor positions of the current module. At start up, the data processing unit queries the current sensor memory to obtain characterization data including error correction factors and relevant specifications that are used by the data processing unit in determining the monitor's output.
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The transducer strip 80 may include the current sensor memory 56 containing characterization data for the current transformers mounted on the support 86. The current sensor memory may also include characterization data for the transducer strip enabling the data processing unit to determine whether a transducer strip is compatible with the remainder of the meter and whether the strip is properly connected to the data processing module. Improper connection or installation of an incompatible transducer strip may cause illumination of signaling lights or a warning message on the meter's display. In addition, the transducer strip 80 may comprise a current module of the power meter with one or more current transformers 54, the multiplexer 52, the current sampling unit 50 and the current sensor memory all mounted on the support 86. A connector 98 provides a terminus for a communication link 102 connecting the current transducer strip (current module) to the data processing module 22.
The branch current monitor may also include one or more errant current alarms to signal an operator or data processing system that manages the facility or one or more of its operations of an errant current flow in one of the monitored branch circuits. When a current having a magnitude greater or lesser than a respective alarm current limit is detected in one of the branch circuits an alarm annunciator is activated to notify the operator or another data processing system of the errant current flow. An alarm condition may be announced in one or more ways, including, without limitation, periodic or steady illumination of a light 71, sounding of an audible alarm 73, display of a message on the meter's display 32 or transmission of a signal from the communications interface 34 to a remote computer or operator.
A commercial power distribution panel commonly supplies a substantial number of branch circuits and a branch current monitor for a distribution panel typically includes at least an equal number of current transformers. Referring to
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The branch current monitor is installed in the distribution panel by mounting the current transformer strips to the panel adjacent to the rows of circuit breakers and by passing each of the branch circuit conductors 88 through a central aperture in one of the toroidal current transformers and connecting the conductors to the respective circuit breakers. The main acquisition board 108 is attached to the electrical panel and the multi-conductor cables 102 are connected to the board. The main acquisition board 108 is preferably housed in a housing. The mains conductors are passed through the apertures in the auxiliary current transformers and the auxiliary current transformers are connected to the main acquisition board. The voltage taps are connected to respective bus bars and to the main acquisition board. The data channel 120 is connected and the branch current monitor is ready for configuration.
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It is to be understood that the current sensor may be any suitable technique, including non-toroidal cores.
One or more of the circuit breakers along the length of the power panel has a tendency to trip if the current levels and/or power levels are too high for the circuit breaker, thus protecting the respective loads from damage. Typically, the tripping of the circuit breakers occurs as a result of the load consuming more power than the rating of the corresponding circuit breaker(s). When the circuit breaker trips a signal is typically received by the monitoring system as a result of a change in the sensed current levels in the power cable indicating the occurrence of the tripped circuit breaker and/or failure of the load. When this occurs, a technician is dispatched to the circuit breaker and/or the load to reset the circuit and repair the load, as needed. However, during this time until the resetting of the circuit breaker and/or repair of the failed load, the operation of the load is compromised. In the case of computer servers in a data center, where continuous up time for the computer servers is of a paramount concern, it is desirable to predict if the circuit breaker is likely to trip so that preventive measures may be taken to avoid such an occurrence.
In general, the circuit breaker operates as a switch that protects the wiring and the load from overheating and shuts off the electricity to the load. Many circuit breakers include a heating element that heats a thermostat inside the breaker as an estimation of the power being provided to the load. While providing a sufficiently large amount of power to the load will trigger the circuit breaker, another source of heat that could trigger the circuit breaker is a loose wire connection to the circuit breaker. The loose wire connection builds up additional heat in the circuit breaker, generally as a result of small sparks that form between the surfaces of the loose wire connection. If a loose wire connection to the circuit breaker can be sensed, as a result of the additional heat being generated by the loose connection, then a technician will be able to properly secure the wire to the circuit breaker so that the circuit breaker does not subsequently trip as a result of the loose connection, and otherwise power is not unnecessarily interrupted to the load, such as one or more servers of a data center.
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In general, the temperature sensor may be associated with the current sensor(s) and/or the power cable(s), which are likewise in turn associated with the other of the current sensor(s) and/or the power cable(s) which are associated with one or more circuit breakers.
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In an alternative embodiment, one or more of the temperature sensors may be associated with one or more of the current sensors.
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The alarm condition and/or the warning condition may further be based upon a combination of the output of one or more of the temperature sensors together with the output of one or more of the current sensors.
In some situations, the temperature variations may be based upon a change in the voltage levels being provided to a particular load. By way of example, the loose connection between the power cable and the circuit breaker may result in undesirable variations in the voltage levels. While a contact based voltage sensor may be provided for each of the power cables, it is preferable that one or more non-contact voltage sensors are supported by or connected to the elongate circuit board. Also, a non-contact voltage sensor may be supported by or enclosed within a respective housing for a current sensor. The non-contact voltage sensor preferably senses a voltage level within a respective power conductor. The output of one or more of the temperature sensors may be associated with one or more of the outputs of the current sensors and/or one or more output of the non-contact voltage sensors to determine a warning condition and/or an alarm condition for one or more of the circuit breakers and/or loads.
The detailed description, above, sets forth numerous specific details to provide a thorough understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuitry have not been described in detail to avoid obscuring the present invention.
All the references cited herein are incorporated by reference.
The terms and expressions that have been employed in the foregoing specification are used as terms of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims that follow,
Claims
1. An energy system comprising:
- (a) a plurality of current sensors, suitable to sense a changing current in a respective power cable, that provide a respective first output;
- (b) a support;
- (c) said current sensors interconnected to said support at spaced apart locations along said support;
- (d) a temperature sensor that provides a second output;
- (e) said temperature sensor interconnected to said support;
- (f) said energy system that receives said respective first output and said second output, and determines characteristics of said energy system based upon said second output.
2. The energy system of claim 1 wherein said current sensors are detachably interconnected to said support.
3. The energy system of claim 1 wherein said current sensors are detachably interconnected to said support by a respective connector.
4. The energy system of claim 1 wherein said temperature sensor is supported by an enclosure where said enclosure encloses one of said plurality of current sensors.
5. The energy system of claim 4 wherein said temperature sensor is enclosed within said enclosure.
6. The energy system of claim 1 wherein said characteristics are used to predict if a circuit breaker associated with a respective power cable is likely to trip.
7. The energy system of claim 1 wherein said characteristics are used to predict if one of a plurality of circuit breakers associated with a plurality of respective power cables is likely to trip.
8. The energy system of claim 1 wherein said characteristics are used to provide an alarm condition.
9. The energy system of claim 1 wherein said characteristics are used to provide a warning condition.
10. The energy system of claim 1 wherein said characteristics are used to provide a normal condition.
11. The energy system of claim 8 wherein said alarm condition is based upon a plurality of said second outputs.
12. The energy system of claim 9 wherein said warning condition is based upon a plurality of said second outputs.
13. The energy system of claim 10 wherein said normal condition is based upon a plurality of said second outputs.
14. The energy system of claim 8 wherein said alarm condition is based upon a relative level of said characteristics.
15. The energy system of claim 8 wherein said alarm condition is based upon an absolute level of said characteristics.
16. The energy system of claim 1 wherein said temperature sensor is supported by said support.
17. The energy system of claim 1 further comprising a plurality of said temperature sensors, each of which is supported by said support.
18. The energy system of claim 1 further comprising a plurality of enclosures each of which is associated with a respective current sensor, a plurality of said temperature sensors each of which is supported by a respective said enclosure and each of which provides a respective said second signal.
19. The energy system of claim 1 further comprising a plurality of said temperature sensors each of which having a respective said second output wherein said characteristics for one of said power cables is determined based upon a plurality of said respective second outputs.
20. The energy system of claim 1 wherein said plurality of current sensors includes three current sensors, suitable to sense a changing current in a respective power cable of a three phase load, that provide a respective first output, three said temperature sensors each of which having a respective said second output, wherein a first one of said respective said first outputs is associated with a respective first one of said second outputs, wherein a second one of said respective said first outputs is associated with a second respective one of said second outputs, wherein a third one of said respective said first outputs is associated with a third respective one of said second outputs, wherein said characteristics for said load is based upon said three said respective said second outputs.
Type: Application
Filed: May 17, 2018
Publication Date: Jun 10, 2021
Applicant: Veris Industries, LLC (Tualatin, OR)
Inventor: Martin COOK (Tigard, OR)
Application Number: 16/613,234