NZ624320B - Electricity meter hot socket detection - Google Patents
Electricity meter hot socket detectionInfo
- Publication number
- NZ624320B NZ624320B NZ624320A NZ62432014A NZ624320B NZ 624320 B NZ624320 B NZ 624320B NZ 624320 A NZ624320 A NZ 624320A NZ 62432014 A NZ62432014 A NZ 62432014A NZ 624320 B NZ624320 B NZ 624320B
- Authority
- NZ
- New Zealand
- Prior art keywords
- meter
- transceiver
- arc condition
- channels
- processor
- Prior art date
Links
- 230000005611 electricity Effects 0.000 title claims abstract description 34
- 238000001514 detection method Methods 0.000 title description 12
- 238000004891 communication Methods 0.000 claims abstract description 25
- 238000011068 load Methods 0.000 claims abstract description 20
- 238000001228 spectrum Methods 0.000 description 12
- 238000000034 method Methods 0.000 description 6
- 238000009434 installation Methods 0.000 description 5
- 238000005259 measurement Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 3
- 210000001847 Jaw Anatomy 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 230000001360 synchronised Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 241001482238 Pica pica Species 0.000 description 1
- 239000003570 air Substances 0.000 description 1
- 239000012080 ambient air Substances 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000000875 corresponding Effects 0.000 description 1
- 230000001066 destructive Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
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- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R22/00—Arrangements for measuring time integral of electric power or current, e.g. electricity meters
- G01R22/06—Arrangements for measuring time integral of electric power or current, e.g. electricity meters by electronic methods
- G01R22/061—Details of electronic electricity meters
- G01R22/063—Details of electronic electricity meters related to remote communication
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R22/00—Arrangements for measuring time integral of electric power or current, e.g. electricity meters
- G01R22/06—Arrangements for measuring time integral of electric power or current, e.g. electricity meters by electronic methods
- G01R22/061—Details of electronic electricity meters
- G01R22/068—Arrangements for indicating or signaling faults
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/66—Testing of connections, e.g. of plugs or non-disconnectable joints
- G01R31/68—Testing of releasable connections, e.g. of terminals mounted on a printed circuit board
- G01R31/69—Testing of releasable connections, e.g. of terminals mounted on a printed circuit board of terminals at the end of a cable or a wire harness; of plugs; of sockets, e.g. wall sockets or power sockets in appliances
Abstract
Disclosed is an electricity meter for metering electrical energy delivered from a voltage source to an electrical load, the meter being disposed between the voltage source and the electrical load. The meter is comprised of blades for connecting the electricity meter to a socket; a transceiver that communicates wirelessly on a plurality of channels of an RF communication system; and a processor. The transceiver measures received signal strength on at least some of the plurality of channels and generates a received signal strength indicator (RSSI) value indicative of the received signal strength on those channels. The processor receives the RSSI values from the transceiver and determines therefrom whether an arc condition exists between the blades and the socket. communicates wirelessly on a plurality of channels of an RF communication system; and a processor. The transceiver measures received signal strength on at least some of the plurality of channels and generates a received signal strength indicator (RSSI) value indicative of the received signal strength on those channels. The processor receives the RSSI values from the transceiver and determines therefrom whether an arc condition exists between the blades and the socket.
Description
ELECTRICITY METER HOT SOCKET DETECTION
FIELD OF THE INVENTION
The present disclosure relates to electricity metering, and more particularly,
to systems, methods, and apparatus for detecting hot socket conditions at an electricity meter
installation.
BACKGROUND
The Smart Grid concept for upgrading electrical systems has brought with it
the change-out of millions of electricity meters. Older electromechanical meters are being
exchanged for newer solid state electricity meters with communication capabilities, and the
majority of these new meters include a whole-house disconnect switch mechanism. Many of
the electricity meters being replaced have been in service at residential locations for years.
An electricity meter installation generally does not get serviced or maintained, so some of the
older meter sockets in which those meters were installed may have deteriorated over time.
Installation of a new electricity meter into a deteriorated meter socket may create a poor
electrical connection even though the meter being installed is in good working order.
Typically, a single-phase ANSI meter has four blades that extend out of a
thermoplastic base. These blades insert into spring loaded jaws of a meter socket that is
typically mounted on the wall of a residence. In some of the older residential locations, the
jaws of the meter socket may have lost the contact force to mate solidly with the meter
blades. An installer may not recognize that one or more blades are not making as good
contact as desired at time of installation.
Poor electrical connection between the meter and socket can create a
situation where an arc can develop within the meter-to-socket interface. There have been
occasions where house fires have resulted from a sustained arc condition of this meter-socket
type.
Attempts have been made to sense "hot socket" conditions by measurement
of blade temperature, socket temperature, or meter temperature. Unfortunately, sensing
temperature of these elements during an arc event requires that the arc exist for a sufficiently
long time to generate intense heating. There is a possibility that by the time the heat is
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detected, the arc condition may sufficiently degrade the equipment to create a dangerous
situation.
There have also been attempts to solve a related problem using AFCI devices
for residential applications. These AFCI devices sense voltage and/or current associated with
a load and attempt to develop a "signature" that is associated with an arc condition. The
characteristics of the arc are typically sensed by looking at different frequencies of noise that
can be present in the voltage and cun
-ent signals on the power line. If an arc is detected, the
AFCI device can open the load current and remove the arc condition if it's on the circuit
being monitored. Other attempted solutions for arc detection have involved sensing the light
generated by an arc.
SUMMARY
This disclosure relates to an electricity meter and method for determining
whether an arc condition exists between the meter and a socket. The electricity meter is used
for metering electrical energy delivered from a voltage source to an electrical load. The
meter is disposed between the voltage source and the electrical load. The meter comprises
blades, a radio frequency (RF) transceiver, and a processor. The blades are for connecting
the meter to the socket. The RF transceiver is used for meter communications, such as for
transmitting collected meter data to a utility head end via a wireless communication network.
In that regard, the RF transceiver will both transmit and receive communications on a given
frequency. The transceiver may also measure received signal strength on a communication
channel or frequency and generate a value indicative of the received signal strength. Such
values are commonly referred to as received signal strength indicator (RSSI) value. The
transceiver may generate RSSI values in the RF communication spectrum for all
communication channels employed by the transceiver for communications. The processor
receives the RSSI values generated by the transceiver and determines therefrom whether an
arc condition exists between the blades and the socket.
The term 'comprising' as used in this specification and claims means
'consisting at least in part of'. When interpreting statements in this specification and claims
which include the term 'comprising', other features besides the features prefaced by this term
in each statement can also be present. Related terms such as 'comprise' and 'comprised' are
to be interpreted in similar manner.
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BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing summary, as well as the following detailed description of
illustrative embodiments of the present application, will be better understood when read in
conjunction with the appended drawings. For the purposes of illustrating the present
application, there is shown in the drawings illustrative embodiments of the disclosure. It
should be understood, however, that the application is not limited to the precise arrangements
and instrumentalities shown. In the drawings:
illustrates an embodiment of an exemplary metering system in which
the arc detection methods disclosed herein may be embodied;
is a schematic of an electricity meter with a transceiver and a
disconnect switch; and
is a diagram illustrating an embodiment of a method for detecting an
arc condition.
DETAILED DESCRIPTION
Disclosed herein are methods and systems for detecting the occurrence of an
arc condition in an electricity meter/socket installation by examining characteristics of radio
frequency (RF) communications conducted by a transceiver of an electricity meter in the
industrial, scientific and medical (ISM) communication spectrum. By keeping a record of the
normal background noise on the ISM channels employed by the meter and detecting a
broadband increase in the noise on all ISM channels, arc detection can be achieved. In one
embodiment, a disconnect switch within the meter can be opened to remove the arc fault. In
other embodiments, other meter measurements, alone or in combination with RF sensing,
may be employed to detect an arc condition, including, for example, current magnitude,
voltage magnitude, and/or temperature information.
provides a diagram of one exemplary metering system 110 in which
the arc detection methods described herein may be employed. System 110 comprises a
plurality of meters 114, which are operable to sense and record consumption or usage of a
service or commodity such as, for example, electricity, water, or gas. Meters 114 may be
located at customer premises such as, for example, a home or place of business. Meters 114
comprise circuitry for measuring the consumption of the service or commodity being
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consumed at their respective locations and for generating data reflecting the consumption, as
well as other data related thereto. Meters 114 may also comprise circuitry for wirelessly
transmitting data generated by the meter to a remote location. Meters 114 may further
comprise circuitry for receiving data, commands or instructions wirelessly as well. Meters
that are operable to both receive and transmit data may be referred to as "bi-directional" or
"two-way" meters, while meters that are only capable of transmitting data may be referred to
as "transmit-only" or "one-way" meters. In hi-directional meters, the circuitry for transmitting
and receiving may comprise a
transceiver. In an illustrative embodiment, meters 114 may be,
for example, electricity meters manufactured by Elster Solutions, LLC and marketed under
the tradename REX. One example of a transceiver that may be employed in such a meter and
used in connection with the arc detection method disclose herein is a Silicon Labs SI4461.
System 110 further comprises collectors 116. In one embodiment, collectors
116 are also meters operable to detect and record usage of a service or commodity such as,
for example, electricity, water, or gas. In addition, collectors 116 are operable to send data to
and receive data from meters 114. Thus, like the meters 114, the collectors 116 may comprise
both circuitry for measuring the consumption of a service or commodity and for generating
data reflecting the consumption and circuitry for transmitting and receiving data. In one
embodiment, collector 116 and meters 114 communicate with and amongst one another using
any one of several wireless techniques such as, for example, frequency hopping spread
spectrum (FHSS) and direct sequence spread spectrum (DSSS).
A collector 116 and the meters 114 with which it communicates define a
subnet/LAN 120 of system 110. As used herein, meters 114 and collectors 116 may be
referred to as "nodes" in the subnet 120. In each subnet/LAN 120, each meter transmits data
related to consumption of the commodity being metered at the meter's location. The collector
116 receives the data transmitted by each meter 114, effectively "collecting" it, and then
periodically transmits the data from all of the meters in the subnet/LAN 120 to a data
collection server 206. The data collection server 206 stores the data for analysis and
preparation of bills, for example. The data collection server 206 may be a specially
programmed general purpose computing system and may communicate with collectors 116
via a network 112. The network 112 may comprise any fomi of network, including a wireless
network or a fixed-wire network, such as a local area network (LAN), a wide area network,
the Internet, an intranet, a
telephone network, such as the public switched telephone network
(PSTN), a Frequency Hopping Spread Spectrum (FHSS) radio network, an ISM mesh
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network, a Wi-Fi (802.11) network, a Wi-Max (802.16) network, a land line (POTS)
network, or any combination of the above.
is a schematic diagram of an embodiment of an electricity meter 300,
which may be one of the meters 114 or collectors 116 in the system of As shown, the
meter 300 may be disposed between an electrical energy source 8 and an electrical load 14,
and it functions to meter electrical energy delivered from source 8 to the load 14 via feeder
lines 320 at a subscriber location. A disconnect switch 304 may be interposed into the feeder
lines 320, for switching between an open position, in which electrical energy is not supplied
to the electrical load 14, and a closed position, in which electrical energy is supplied to the
electrical load.
The meter 300 also comprises a processor 302, such as a microprocessor,
which executes computer-readable instructions (program code) that may be stored within a
memory (not shown) of the meter. These computer-executable instructions, when executed
by the processor, cause the processor to perform various functions within the meter, such as
determining energy consumption and operating other components with the meter. As further
shown, the meter 300 also includes a transceiver 350 which may be used by the processor to
transmit and receive infon -nation to/from a meter network, such as the meter network
illustrated in In one embodiment, the transceiver may comprise a Silicon Labs
SI4461.
The transceiver 350 may be configured to measure received signal strength
on an RF communication frequency or channel of a wireless communication network and to
generate a receive signal strength indicator (RSSI) value therefrom. RSSI is an indication of
the power level being received by the antenna of the transceiver. Typically, the higher the
RSSI value, the stronger the signal. RSSI can be used internally in a transceiver to determine
when the amount of radio energy in a channel is below a certain threshold at which point the
transceiver may be clear to transmit on the channel. Conversely, an RSSI value above a
certain threshold may be an indication that another device may be transmitting on the
channel, in which case the transceiver may try to lock-on to the signal being transmitted on
that channel.
The transceiver 350 may be employed by the processor to communicate with
a remote utility monitoring location 360. As further shown, the meter 300 may further
comprise a current sensor 330 and a source-side voltage sensor 340 that may provide current
and voltage signals to the processor 302 to be used in determining energy consumption.
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According to the arc detection methods described herein, meters in a meter
communication network that employs ISM mesh communications, such as the meters
illustrated in and may be configured to detect arc conditions based on an
examination of the signal strength present on the frequencies
(i.e., channels) employed in the
communication system. Metering nodes (e.g., meters 114 and collectors 116) in an ISM
mesh network typically scan all frequencies within the ISM communication band to detect a
signal to receive. For example, the communication system may employ as many as twenty-
five (25) or even fifty (50) discrete frequencies/channels. The transceiver in a meter typically
scans each frequency in an attempt to detect a transmission from another node in the network
on that frequency. When scanning a given channel, the transceiver will measure the signal
strength on that channel and will generate a received signal strength indicator (RSSI) value
indicative of the detected RF power on that channel. The transceiver may then compare the
RSSI value to a threshold to make a determination as to whether another device is attempting
to transmit on that channel. If so, the transceiver may attempt to lock-on to the signal being
transmitted on that channel.
is a flow diagram illustrating a method of detecting arc conditions
using detected RF energy, in particular RSSI values, to determine whether an arc condition is
present, in accordance with one embodiment. The method may be performed using a meter
such as the one illustrated in however, it should be appreciated that the method
disclosed herein may be implemented in any suitable meter configuration that employs an RF
transceiver. In this embodiment, it is assumed that the meter transceiver is an ISM mesh radio
or other radio device able to detect signals within the ISM communication band. While a
non-synchronous ISM system is already scanning at all frequencies within the ISM frequency
band, a synchronous system can also be adapted to periodically look at RSSI magnitudes to
determine if an arc condition exists. Thus, the methods disclosed herein can be implemented
in any wireless networking communication system for wireless meter reading.
In accordance with the present embodiment, as shown in at step 402,
the transceiver (e.g., transceiver 350 of may measure received signal strength on
various frequencies/channels within its frequency spectrum, during normal scanning of those
channels in connection with its normal communication functions. At step 404, the processor
of the meter may record, or store, the RSSI values measured on those channels, for example,
in the internal memory of the meter's processor (e.g., processor 302) or in a memory separate
from the processor. At some point thereafter, in step 406, the processor may compare newly
received RSSI values from the transceiver 350 with the previously obtained values stored in
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step 404. Based on this comparison, in step 408, the processor may then determine whether
an arc condition exists within or around the meter socket. Several different methods for
making this detell iination based on the RSSI comparison are discussed in more detail below.
If an arc condition has been determined to exist, then at step 410, an internal disconnect
switch within the meter (e.g., disconnect switch 304) may be operated to the open position,
thereby disconnecting the meter from the source and removing the meter load and thereby the
arc condition. At step 412, the removal of the arc condition may then be verified and, at step
414, the processor may generate a signal indicating that an arc condition was detected and
send that signal to the utility via the meter transceiver. If, on the other hand, no arc condition
is detected in step 408, then control may pass back to step 402 where the transceiver
continues its normal scanning operations and repeats the process.
An electrical arc condition is characterized by extremely high temperatures
(thousands of degrees Kelvin). In experiments associated with this disclosure, it was
determined that a welding arc has energy not only at hundreds of kHz and in the light
spectrum, but also there is energy within the ISM 900 MHz spectrum. Effectively, the arc
energy develops a broadband "signature" RF noise signal across almost all frequencies in the
RF spectrum.
In testing for this arc problem, a meter with special filinware was used to
evaluate the instantaneous RSSI values for all communication channels in the 900 MHz ISM
spectrum. A condition was set up at a residential site where no arc existed and the
background noise RSSI values were recorded. Then an arc was generated and with the arc
present, the RSSI values were again read for the ISM 900 MHz channels. It was determined
from this set of tests that the RSSI values for all the narrowband channels across the ISM
spectrum increased 10-15 dB when the arc was present. This type of result at several feet
away from the arc means that the meter can use the transceiver or ISM radio — in particular its
ability to measure RSSI on the ISM channels - to detect the presence of an arc condition.
This is especially true if the arc condition is situated in close proximity to a radio antenna of
the transceiver, as it would be for a case where the arc exists at the connection of the meter
blades to the meter socket.
Because an arc's energy characteristic can follow an AC voltage and/or
current waveform, extinguishing at zero current crossover and reigniting shortly afterwards as
the voltage builds up, it is preferable to scan for RSSI values away from the zero crossover of
the AC voltage or current. This scan placement or timing within the AC waveform can be
incorporated into the "arc scan" method of along with comparisons between average
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broadband background noise (RSSI values) and newly measured broadband noise (RSSI
values).
Because the transceiver, or meter radio, should be able to scan for an arc
condition almost instantaneously (e.g., less than 1 msec), the arc condition may be detected
rapidly upon occurrence and an early warning signal may be generated to the utility. As
illustrated in step 410 of the meter may also make a decision to open an internal
disconnect switch of the meter to remove the meter loading and thereby eliminate the arc
condition. An arc condition requires a finite level of current to exist (typically a minimum of
at least 0.5-1 Amp for most metals), so by opening the disconnect switch all loads at the
subscriber location will be removed and the arc condition will be extinguished. This is
particularly important since even a moderately high current arc condition can be extremely
destructive in a short amount of time. After the disconnect switch is operated to the open
position, the removal of the arc condition may be verified.
Determining whether an arc condition exists in step 408 of may
incorporate a variety of information and techniques. In one embodiment, the determination is
made as described in connection with by simply monitoring ongoing RF noise levels
(RSSI values) for all channels in the ISM spectrum and then comparisons the new readings to
the previously stored readings (e.g., stored within the internal memory of the meter
processor). If the comparisons result in immediate broadband increases in noise (e.g., a
threshold increase of 10-15 dB or more) covering most, if not all ISM channels, this may be
determined to be an arc condition. As mentioned earlier, arc noise can follow the AC current
waveform so an increase in RF broadband noise at the peak of the current waveform coupled
with a significant reduction of RF broadband noise at or near zero voltage/current crossover
may also be determined to be an indication of an arc.
In other embodiments, the method for detemiining whether an arc condition
exists may directly compare the per-channel RF noise (RSSI value) at the peak of the current
waveform as compared to the noise (RSSI value) on the same channel at or near the zero
crossing of the current waveform. Alternatively, an arc condition may be indicated when the
number of channels on which the RSSI is greater than the previous RSSI readings for the
same channels by more than, for example 15 db, is greater than, for example 80% of the total
number of channels scanned. In various embodiments, the threshold db value (e.g., 15db)
and threshold number of channels (e.g, 80%) may be configurable and/or may initially be set
to default values. Preferable, the change in db value is in the range of 10 db to 20 db.
Preferably the threshold number of channels is in the range of 70% to 80%.
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In other embodiments, other meter measurements, such as current
magnitude, voltage magnitude and/or meter temperature, may be coupled with the RF arc
sensing method disclosed above to enable improved prediction of arc conditions, or those
other measurements may be used in a standalone manner. For example, a sudden 10%
reduction in current magnitude coupled with increased RF broadband noise or increased
harmonic noise could be predictive of an arc condition (arc voltage would decrease normal
current). Similarly, a sudden 10% reduction in input voltage coupled with increased RF
broadband noise or increased harmonic noise could be predictive of an arc condition (arc
voltage at the input blades would decrease sensed input voltage). Also, a continually
increasing meter temperature coupled with increased RF broadband noise and/or increased
harmonic noise could be predictive of an arc condition. In yet another embodiment, an
increase in harmonic content of the input AC voltage and/or current waveforms alone or
coupled with an increase in broadband RF noise could be used to trigger an arc condition
alert. Any, or all of these conditions, in any possible combination, could be included as part
of the arc detection methods disclosed herein. And any or all of these conditions and/or
measurements may be utilized in a standalone detection system that relies on broadband RF
noise levels and/or harmonic noise as a part of the arc detection system.
In an alternate embodiment, an unsafe condition may be detected by
computing a relative meter temperature using the measured internal meter temperature and
several other channels of data that may be measured by the meter or downloaded to the
meter. For example, the following channels may be used: (i) internal meter temperature as
measured by the meter electronic assembly; (ii) per phase current, i.e. rms amps, as measured
by the meter; and/or (iii) temperature profile, where a temperature profile may be
downloaded on a periodic basis, e.g. daily, and provide the approximate ambient air
temperature for each time period of the day.
In one embodiment, for an averaging window, e.g. 5 minutes, the meter
records the above quantities (e.g., in an internal memory of the meter processor) and these
channels of interval data may be read from the meter. In addition, the meter may compute a
relative temperature, by first subtracting a temperature offset from the internal meter
temperature, where the temperature offset is computed based on the average per phase current
measured by the meter. The per phase current temperature offset may be computed or
provided as an input, where typically the temperature offset is zero degrees at zero current to
a maximum temperature offset, e.g. 15 degrees C, at the meter maximum rated current, e.g.
200A. The computed relative temperature may then be compared to the downloaded
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temperature for the corresponding time period of the day, and if the difference between the
relative temperature and the temperature profile value is greater than a configurable
threshold, the meter flags an "over temperature" warning and can optionally open the service
disconnect switch.
In other embodiments, additional inputs may be used to further define the
relative temperature computation and could be based on: (i) different ambient temperature
profiles based on meter direction and estimated sun loading; and/or (ii) a parameter based on
the measured power supply load. Optionally, the power supply load can be estimated based
on the known duty cycle of key loads, e.g. radio transmit duty cycle.
The above temperature-based alerting mechanism improves on simple
temperature-based methods that do not account for differences in ambient temperature or
other loads that affect the internal meter air temperature.
is understood that any or all of the arc detection methods, processes, and
systems described herein, such as, for example, the steps illustrated in may be
embodied in the form of computer executable instructions (i.e., program code) stored on a
computer-readable storage medium which instructions, when executed by a processor (e.g.,
processor 302 of , perform and/or implement the methods, processes, and systems
described herein. Computer readable storage media include both volatile and nonvolatile,
removable and non-removable media implemented in any method or technology for storage
of information. Computer readable storage media include, but are not limited to, RAM,
ROM, EEPROM, flash memory or other memory technology, CDROM, digital versatile
disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk
storage or other magnetic storage devices, or any other medium which can be used to store
the desired information and which can be accessed by a computer. These storage media may
be integrated into processor 302 of or may be separate components within the meter
300, for example. As used herein, the term "computer readable storage media" does not
include signals.
While the disclosure is described herein using a limited number of
embodiments, these specific embodiments are for illustrative purposes and are not intended to
limit the scope of the disclosure as otherwise described and claimed herein. Modification and
variations from the described embodiments exist. The scope of the invention is defined by
the appended claims.
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Claims (12)
1. An electricity meter for metering electrical energy delivered from a voltage source to an electrical load, said meter disposed between said voltage source and said electrical load, the meter comprising: blades for connecting the electricity meter to a socket; a transceiver that communicates wirelessly on a plurality of channels of an RF communication system, the transceiver measuring received signal strength on at least some of the plurality of channels and generating a received signal strength indicator (RSSI) value indicative of the received signal strength on those channels; and a processor that receives the RSSI values from the transceiver and deterinines therefrom whether an arc condition exists between the blades and the socket.
2. The electricity meter of claim 1, wherein the RF communication system comprises an ISM mesh networking system.
The electricity meter of claim 2, wherein the ISM mesh networking system comprises a utility, wherein the utility is signaled when the processor determines that an arc condition exists.
4. The electricity meter of claim 1, wherein the processor generates a warning signal when an arc condition is determined to exist.
5. The electricity meter of claim 1, further comprising an internal disconnect switch, wherein when an arc condition is determined to exist, the processor operates the internal disconnect switch to an open position to remove a meter load and thereby eliminate the arc condition.
6. The electricity meter of claim 5, wherein the meter is configured to verify that the arc condition has been removed.
The electricity meter of claim 1, wherein the transceiver is in close proximity to the blades.
8. The electricity meter of claim 1, wherein the processor determines whether an arc condition exists within 1 millisecond. 7024998_1
9. The electricity meter of claim 1, wherein the transceiver detects RSSI values in the ISM 900 MHz band.
10. The electricity meter of claim 1, wherein the metering processor is configured to deteimine that an arc condition exists when at least 70% of the RSSI values measured by the transceiver on the channels of the RF communication system are determined to have increased by at least 10 db.
The electricity meter of claim 1, wherein the meter is configured to store a record of RSSI values for each communication channel, and the processor is configured to determine whether an arc condition exists by comparing the stored RSSI values for a communication channel with more recently measured RSSI values of the same communication channel at the peak and at or near the zero crossing of a current or voltage waveform.
12. The electricity meter of claim 1, wherein the processor is configured to receive temperature, current, voltage, and harmonic content and determine therefrom, in combination with the RSSI values, whether an arc condition exists. An electricity meter for metering electrical energy delivered from a voltage source to an electrical load, the meter disposed between said voltage source and said electrical load, the meter being substantially as hereinbefore described with reference to the accompanying drawings. 7024998_1 4b 114b 114b 114b 114b Meter Meter Meter Meter Meter 114a Meter 114a 114b Meter Meter Collector Meter N etwork- Data Collection Server Meter 114a Collector 114a 114a Meter Meter 114a Meter 114b r114b 114b 114b Meter Meter Meter Meter Meter Measure RSSI for - Communication Channels 4 in the 900 MHz ISM band — Record RSSI Values Compare Recently Received RSSI Values with Recorded RSSI Values Open Internal Disconnect Switch Verify Arc Condition has been Removed Generate Warning Signal and Send to Utility
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US201361818037P | 2013-05-01 | 2013-05-01 | |
US61/818037 | 2013-05-01 |
Publications (2)
Publication Number | Publication Date |
---|---|
NZ624320A NZ624320A (en) | 2015-02-27 |
NZ624320B true NZ624320B (en) | 2015-05-28 |
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