U.S. patent application number 09/962564 was filed with the patent office on 2002-04-11 for point of use digital electric energy apparatus with real-time dual channel metering.
Invention is credited to Shincovich, John T..
Application Number | 20020042683 09/962564 |
Document ID | / |
Family ID | 22884187 |
Filed Date | 2002-04-11 |
United States Patent
Application |
20020042683 |
Kind Code |
A1 |
Shincovich, John T. |
April 11, 2002 |
Point of use digital electric energy apparatus with real-time dual
channel metering
Abstract
An apparatus and method for measuring electric power consumed at
a use site includes voltage and current sensors on each site
conductor which are sampled at a sample interval to generate
sampled voltage and current signals. The voltage and current
signals are converted to digital values which are used to directly
calculate power consumption values. The digital voltage and current
magnitude values are stored in a memory either prior to or
subsequent to the power consumption calculations.
Inventors: |
Shincovich, John T.; (North
Canton, OH) |
Correspondence
Address: |
YOUNG & BASILE, P.C.
3001 West Big Beaver Road, Suite 624
Troy
MI
48084-3107
US
|
Family ID: |
22884187 |
Appl. No.: |
09/962564 |
Filed: |
September 25, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60235122 |
Sep 25, 2000 |
|
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Current U.S.
Class: |
702/61 |
Current CPC
Class: |
H04B 2203/5458 20130101;
H04B 3/54 20130101; H04B 2203/5433 20130101; H04B 3/546
20130101 |
Class at
Publication: |
702/61 |
International
Class: |
G06F 019/00; G01R
021/00; G01R 021/06 |
Claims
What is claimed is:
1. An apparatus for measuring electric power usage at a use site
comprising: a current sensor and a voltage sensor coupled to at
least one phase of electric power service to a use site for sensing
current and voltage, respectively, of electricity passing to the
use site, the sensors producing current and voltage signals
indicative of sensed current and voltage; means for sampling
current and voltage signals at a sample interval and producing
sampled current and voltage values; an anlog-to-digital converter,
acting on the current and voltage sampled signals, for producing a
plurality of digital signals at predetermined sample intervals
indicative of the magnitude of the sampled current and voltage; and
a processor, responsive to the plurality of digital current and
voltage signals, for calculating an amount of electric power
passing to the use site based on all of the sensed and sampled
current and voltage values.
2. The apparatus of claim 1 further comprising: a memory, coupled
to the processor, for storing the sampled current and voltage
digital values and the calculated power values over predetermined
time periods.
3. The apparatus of claim 1 wherein: one current sensor and one
voltage sensor are coupled to each leg of electric power service to
the use site; and the processor, response to the plurality of the
digital current and voltage signals on each phase of electric
power, for calculating an amount of electric power passing to the
use site on each phase.
4. The apparatus of claim 1 further comprising: the processor
having a remote data transmission capability for remotely
transmitting the power values.
5. A method of measuring electric power consumed at a use site
comprising the steps of: separately sensing the voltage of each
incoming power conductor to the use site; separately sensing the
current on each incoming power conductor to the use site; sampling
each voltage and current at a sample rate and outputting sample
voltage and current values; converting each sample voltage and
current value to a digital voltage and current magnitude value; and
calculating power consumed at the use site using the digital
voltage and current magnitude values.
6. The method of claim 5 further comprising the step of: storing
each of the digital magnitude voltage and current values in a
memory either after or prior to power calculation.
7. The method of claim 5 wherein the step of calculating power
consumption comprises the step of: calculating total kilowatt hours
consumed at the use site from the instantaneous voltage and current
digital values.
Description
CROSS REFERENCE TO CO-PENDING APPLICATION
[0001] This application claims the benefit of the filing date of
co-pending provisional U.S. Patent Application Serial No.
60/235,122, filed Sep. 25, 2000 and entitled POINT OF USE DIGITAL
ELECTRIC ENERGY MEASUREMENT, CONTROL AND MONITORING APPARATUS.
BACKGROUND
[0002] The present invention relates, in general, to apparatus for
measuring and controlling the supply of electric energy at a use
site.
[0003] In the electric utility industry, watthour meters are
typically employed to measure electric power used at a building or
home site. A socket housing is mounted on a convenient wall of the
residence or commercial building and contains pairs of line and
load terminals which are respectively connected to the electric
utility line conductors and the building load distribution
conductors. The terminals typically receive blade contacts on a
plug-in watthour meter to complete an electric circuit through the
meter between the line and load terminals.
[0004] Plug-in socket adapters and socket adapters/extenders, both
hereafter referred to simply as socket adapters, are designed to
plug into the meter socket housing terminals. Such socket adapters
are employed to convert a ringless style socket to a ring style
socket or to extend the mounting position of the jaw terminals in
the socket outward from the socket for mounting various electrical
equipment, such as test devices or survey recorders, in the socket.
The watthour meter is then plugged into jaw contacts carried within
the socket adapter. The socket adapter jaw contacts are connected,
either integrally or via separate electrical connections, to blade
terminals extending rearwardly of the socket adapter housing for
plug-in engagement with the socket terminals or jaw contacts.
[0005] Meter reading personnel periodically inspect each meter site
and record utility meter readings, either visually or by using a
probe to retrieve power usage data stored in solid state memory of
the watthour meter.
[0006] To increase data collection efficiency and reliability,
watthour meters are now available with interface equipment designed
to permit remote interrogation of the meter and transmission of
electric power usage data. Utility meters located at each customer
site are connected in data communication to a central billing
facility via various communication methods, including power line
signal transmission, dedicated signaling lines, use of the public
telephone switching network, and radio frequency signal
transmission.
[0007] Prior automatic meter readers sense the instantaneous
voltage and currents applied to a use site. These instantaneous
values are measured at a sampling interval and digitized. The
digital instantaneous sample values representative of the
instantaneous voltage and current at each sample interval are
stored in a memory. Subsequent calculations are performed on the
sampled voltage and current values.
[0008] However, prior automatic meter readers average the voltage
and current data over each sampling interval to obtain an average
voltage and current which is considered representative of the
instantaneous voltage and current during the entire sampling
interval. It is these average values which are used in calculating
power consumed at the use site, such as total kilowatt hours, etc.
However, this leads to a lower measurement accuracy due to the
averaging.
[0009] Thus, it would be desirable to provide an electric energy
measurement apparatus which provides a higher measurement accuracy
than that possible using prior automatic meter reading
techniques.
SUMMARY OF THE INVENTION
[0010] The present invention is an electric energy measurement
apparatus which is capable of measuring instantaneous voltage and
current at a use site and then using digitized instantaneous
voltage and current values to calculate total power consumed and
other power values, including kilowatt hours, with a high degree of
measurement accuracy.
[0011] In one aspect, the electric energy measurement apparatus and
method include voltage and current sensors for measuring the
voltage and current on each of at least two power conductors at the
use site. The instantaneous voltage and current values measured by
the voltage and current sensors are sampled at a sampling interval
and the sensor outputs converted to digital values which are stored
in a memory for each sample.
[0012] Simultaneous with or subsequent to the storing of the
digital voltage and current values in the memory, the digital
voltage and current values are used in power calculations to
generate power values, such as total kilowatt hours consumed at the
use site on each conductor or phase during the sampling interval.
These power calculations are totaled over any time period to
determine the total power consumed at the use site. This provides a
more accurate power measurement which overcomes the less than
accurate averaging measurement techniques employed in prior art
automatic meter readers.
[0013] The digital voltage and current values are stored for each
leg or phase of electric power supplied to the use site. This
enables power calculations to be performed on each phase for
separate power consumption values.
[0014] The measurement apparatus is capable of downloading the
stored power calculation values to the remote site for further
processing and/or analysis at any time so as to conserve memory
space, etc.
BRIEF DESCRIPTION OF DRAWINGS
[0015] The various features, advantages and other uses of the
present invention are more apparent by referring to the following
detailed description and drawing in which:
[0016] FIG. 1 is a schematic diagram of an electric energy
management apparatus according to the present invention;
[0017] FIG. 2 is an exploded, perspective view showing the electric
energy management apparatus according to the present invention
mountable in a watthour meter socket;
[0018] FIG. 3 is a perspective view of the electric energy
management apparatus without the internal circuit board, the
disconnect switch and the shell;
[0019] FIG. 4 is a perspective view of the electric energy
management apparatus shown in FIG. 3 including the optional
disconnect switch;
[0020] FIG. 5 is a side elevational view of the housing of the
electric energy management apparatus with a portion of the sidewall
of the housing removed to show the internal components of the
electric energy management apparatus of the present invention;
[0021] FIG. 6 is a front elevational view of the circuit board of
the electric energy management apparatus shown in FIG. 5;
[0022] FIG. 7 is a block diagram of the major components of the
electric energy management apparatus at one customer use site;
[0023] FIGS. 8A, 8B, 8C, and 8D are detailed schematic diagrams of
the circuitry of the electric energy management apparatus mounted
on the circuit board shown in FIGS. 5 and 6;
[0024] FIGS. 9A and 9B are flow diagrams of the electric energy
management apparatus control program;
[0025] FIG. 10 is a flow diagram of the power demand windows
control sequence of the present electric energy management
apparatus;
[0026] FIG. 11 is a schematic diagram of the disconnect switch
control circuitry used with the optional disconnect switch shown in
FIG. 4;
[0027] FIG. 12 is a graph depicting out-of-specification
voltages;
[0028] FIG. 13 is a flow diagram of the "out-of-spec" energy
detection sequence;
[0029] FIG. 14 is a flow diagram depicting the tamper detection
sequence;
[0030] FIG. 15 is a side elevational view of the electric energy
management apparatus depicting a partially removed position of the
housing from the meter socket;
[0031] FIG. 16 is a side elevational view, similar to FIG. 15, but
showing the housing blade terminals in a fully separated position
with respect to the socket jaw contacts;
[0032] FIG. 17 is a side elevational view of a meter installation
depicting the electric energy measurement apparatus of the present
invention mounted in a ringless style meter socket;
[0033] FIG. 18 is a flow diagram of the telephone interrupt and
non-interrupt control sequence; and
[0034] FIG. 19 is a diagram of the optical communication
circuit.
DETAILED DESCRIPTION
[0035] Referring now to the drawing, there is depicted a point of
use, digital, electrical energy measurement, control and monitoring
apparatus for use at individual utility customer sites which has
connectivity through a global telecommunication network to a
centralized computer control system.
Central Utility
[0036] As shown in FIG. 1, a central utility company site is
depicted generally by reference number 10. The central utility site
10 may be the central business office of the utility, a generating
station, etc., where utility billing information is accumulated,
tabulated and recorded. A central processing unit 12 is located at
the central site 10. The central processing unit 12 may be any
suitable computer, such as a mainframe, a PC, a PC network,
workstation, etc., having the capacity of handling all of the
utility company customer billing transactions and/or the remote
data communications described hereafter. The central processing
unit 12 communicates with a memory 14 which stores, identification
data specific to each utility customer, as well as other data
regarding the power usage of each customer. The memory 14 may
include both hard disc storage memory and on-board memory. Although
high voltage, electrical power distribution lines denoted generally
by reference number 16 for a three-wire, single-phase electrical
system, are shown as extending between the central utility site 10
to each utility customer 18, 19, etc., it will be understood that
the electrical power distribution lines 16 may extend from a
separate electrical power generating site with appropriate voltage
transformations to each customer site, and not directly from the
central utility site 10. Further, it will be understood that the
electrical power distribution lines 16 may provide three-phase
power to any customer site.
[0037] As shown in FIG. 1, various input and output devices, such a
keyboard, printer(s) 13, display terminals or monitors 15, etc.,
may also be connected to the central processing unit 12 as is
conventional. In addition, one or more modems 20 are connected to
the central processing unit 12 at the central utility site 10 and
to a conventional telephone wiring network denoted generally by
reference number 22. The telephone wiring network 22 may be
conventional telephone wires, as well as fiber optics, satellite,
microwave, cellular telephone communication systems and/or
combinations thereof. The modem 20, which may be any conventional
modem, functions in a known manner to communicate data between a
processor and the telephone network.
[0038] Also stored in the memory 14 are the various software
control programs used by the central processing unit 12 to
automatically communicate with the electrical energy management
apparatus at each utility customer 18, 19 as described hereafter.
The memory 14 also stores the power usage data for each utility
customer 18, 19 as well as various billing routines utilized by a
particular utility company.
[0039] Generally, the software control program stored in the memory
14 is a menu driven database capable of handling multiple
simultaneous calls to a number of remote apparatus at the customer
sites 18, 19. The control program stores each customer's power
usage in accumulated KWH and KVA, for example, and instantaneous
voltage, current and power factor measurements. Also, the control
program generates periodic summary printouts via the printer
13.
[0040] The control program enables the utility to remotely program
each energy management apparatus from the central site 10. Such
programmable features include time, date and year data, a
multi-level security code for communication access, receive call
and originate call modes, line voltage quality set points, start
and end times for multiple demand billing period intervals, i.e.,
three intervals in each 24 hour period, the date, time and duration
of a communication window for communication with the central site
10, etc.
[0041] Various main system menu screens may be generated by the CPU
12 to enable communication with any of the remote units. Further
details concerning the generation and use of such menu screens can
be had by referring to U.S. Pat. No. 5,590,179, the entire contents
of which are incorporated herein by reference.
[0042] According to a unique feature of the present automatic meter
reader apparatus, CPU 12 communicates with a global
telecommunications network that is separate from the conventional
telephone line network 22 through an interface including a modem
connection 20 to an Internet service provider (ISP) 20 which
communicates with a worldwide telecommunications network, such as
the Internet or world wide web. The CPU 12 can generate an
appropriate identification number (I.D.) or address for any of the
remote units. This I.D. can be transmitted by the ISP 20 through
the Internet 21 to any of the individual use sites 18, 19, etc.
Remote Utility Customer
[0043] As shown in FIGS. 1 and 2, a plurality, such as tens or even
hundreds or thousands of utility customer sites 18, 19, are
connected to the electrical power distribution network 16 at remote
locations of varying distances from the central utility company
site 10.
[0044] As is conventional, each utility customer site 18, as shown
in FIG. 1, includes a conventional utility meter socket 30 having a
plurality of internally mounted jaw contacts or terminals 32 which
are connected to the single-phase three-wire line conductors of the
electrical distribution network 16. Although not shown in FIG. 1,
the separate jaw terminals 32 in the socket 30 are connected to the
individual service or load conductors at each utility customer site
18. In a conventional application, the socket 30 is mounted at a
suitable location at the utility customer site 18, such as on an
exterior wall, with the load conductors extending from the socket
30 to the building wiring circuits.
Remote Unit
[0045] A digital, electric energy management apparatus (hereafter
"remote unit") 34 is provided for recording, measuring, controlling
and monitoring electrical power usage at a particular customer site
18. The remote unit 34 has a plurality of outwardly extending,
blade-type, electrical terminals 36 which electrically engage the
jaw contacts or terminals 32 in the socket 30.
[0046] As shown in FIGS. 1 and 2, and in greater detail in FIGS. 3,
4 and 5, the remote unit 34 of the present invention, in a
preferred embodiment, includes a base denoted generally by
reference number 40. The base 40 is snap-in connectable in the
meter socket 30. However, according to the present invention, the
base 40 includes internally mounted electrical energy measurement
and telecommunication circuits as described in greater detail
hereafter. The use of the base 40 to house the automatic meter
reading circuitry is a preferred embodiment of the present
invention. It will be understood, however, that such electrical
energy measurement and control circuitry, as described hereafter,
can also be mounted at each customer site 18, 19 by other means,
such as in an enclosure separate from a standard watthour meter and
the meter socket.
[0047] In general, the remote unit 34 includes a two-part housing
formed of the base 40 having a base wall 42 and a shell 44 which
are releasably joined together by a snap-in and rotate connection.
As described hereafter, a plurality of electrical terminals 34 are
mounted in the base 40. The electrical terminals 47 are provided in
the base 40 in any number, type and arrangement depending upon the
electrical power service for a particular application. By way of
example only, the electrical terminals 47 are arranged in the base
40 in a first pair of line terminals 54 and 56 and a second pair of
load terminals 58 and 60.
[0048] A peripheral flange 48 is formed on the base 40 which mates
with a similarly formed flange 33 on the watthour meter socket or
housing 30 for mounting the remote unit 34 to the watthour meter
socket 30. A conventional seal or clamp ring 62, such as a seal
ring disclosed in U.S. Pat. No. 4,934,747, the contents of which
are incorporated herein by reference, is mountable around the
mating flanges 48 and 33 to lockingly attach the remote unit 34 to
the socket 30 and to prevent unauthorized removal of or tampering
with the remote unit 34.
[0049] It will also be understood that the remote unit 34 and the
socket 30 may be configured for a ringless connection. In this type
of connection, not shown, the cover of the socket 30 is provided
with an aperture which is disposable over the remote unit 34. The
cover is locked to the socket 30 enclosure after the remote unit 34
has been inserted in the socket 30 and through the aperture in the
cover.
[0050] The base 40 and the base wall 42 has generally circular
configuration centered within an integrally formed annular side
wall 44 which terminates in an outer edge 46. The flange 48
projects radially outward from the sidewall 44 at the general
location of the base wall 42. A plurality of circumferentially
spaced notches 50 are formed in the flange 48 for reasons which
will be described in greater detail herein.
[0051] At least one and preferably two ground tabs 51, only one of
which is shown in FIG. 3, are mounted on the exterior surface of
the base wall 42 and have an radially outer end which is positioned
within one of the notches 51 as shown in FIG. 3. The ground tabs 51
are adapted to engage a ground connection in the meter socket 30,
as is conventional and as is described in greater detail
hereafter.
[0052] The shell 44 has a generally cylindrical configuration
formed of a sidewall 45 and an end wall 53. An annular flange 47
projects radially from one end of the sidewall 45 as shown in FIGS.
2 and 5. The flange 47 has a stepped shape formed of a radially
extending leg and an axially extending leg. The flange 47 overlays
the flange 48 on the base 40 and receives the sealing ring 37
thereover as described above.
[0053] A plurality of arcuate slots 49, such as three slots 49 by
way of example only, are formed in the radially extending leg of
the flange 47. A generally L-shaped lock arm 51 projected
interiorly from the radially extending leg of the flange 47 along
one inside edge of each slot 49, as shown in FIG. 5. The L-shaped
lock arm 51 is alignable with one of the notches 51 in the base 40
when the shell 44 is joined to the base 40. Rotation of the shell
44 relative to the base 40 causes the lock arm 51 to slide
underneath the bottom edge of the flange 48 on the base 40 to lock
the shell 44 to the base 40.
[0054] It will be understood that alignable apertures may be formed
in the flange 47 of the shell 44 and the flange 48 of the base 40
in the rotated, locked position for receiving a seal member, such
as a conventional watthour meter seal ring, not shown, to lockingly
attach the shell 44 to the base 40 and to provide an indication of
tampering with the remote unit 34 after the remote unit 34 has been
mounted on the socket 30.
[0055] As also shown in FIGS. 1 and 2, and in greater detail in
FIG. 5, the end wall 53 of the shell 44 is provided with an
aperture 55 which has an under notch or undercut formed about the
periphery of the aperture 55 as shown in FIG. 5. The aperture 55 is
adapted for receiving a transparent cover 57, formed, by example,
of Lexan, and having a notched peripheral edge which fits within
the undercut formed about the periphery of the aperture 55. A
plurality of posts 59 project inwardly from the undercut
surrounding the aperture 55 in the end wall 53 of the shell 44 and
are adapted to engage apertures formed about the periphery of the
cover 57 to align and mount the cover 57 to the end wall 53.
Fasteners, such as lock nuts, not shown are mountable over the
posts 59 to lock the cover 57 in the end wall 53.
[0056] Although not shown in FIG. 5, portions of the transparent
cover 57 are masked or blacked out to provide separate windows, one
for the display 222 and one for the opto-communication port
134.
[0057] A plurality of apertures 52 are formed in the base wall 42
at the normal jaw contact positions of a watthour meter. For the
single phase remote unit 34 described herein by way of example
only, four apertures 52 are formed in the base wall 42 and
respectively received the line blade terminals 54 and 56 and the
load blade terminals 58 and 60. The blade terminals 54, 56, 58 and
60 have one end portion disposed interiorly within the base 40
extending away from one side of the base wall 42 and an external
portion, shown in FIG. 5, which projects exteriorly of the opposed
surface of the base wall 42 and adapted to slidably engage the jaw
contacts 32 in the watthour meter socket 30.
[0058] Although not shown, one of the apertures formed in the
exterior portion of each blade terminal 54, 56, 58 and 60 can
receive a lock member, such as a cotter pin, conventionally used in
watthour meters, to fixedly secure each blade terminal 54, 56, 58
and 60 to the base wall 44.
[0059] A plurality of bosses 62, such as three bosses by way of
example only, are formed on the base wall 42 and project therefrom
to co-planar upper ends as shown in FIG. 5. Each boss 62 can be
solid or hollow, but has an upper end bore 64 adapted to receive a
fastener, such as a screw, for securing a circuit board 66
containing the remote unit 34 circuitry thereon. Thus, the bosses
62 form a support for the circuit board 66 as shown in FIG. 5. This
spaces the circuit board 66 above the blade terminals 54, 56, 58
and 60 as well as above an optional disconnect switch 70.
Disconnect Switch
[0060] The provision of a disconnect switch 70 is optional in the
remote unit 34 of the present invention. However, the disconnect
switch 70 provides valuable features when used in the tampering
detect sequence described hereafter. The disconnect switch 70 may
also be remotely controlled by the central utility site 10 to
control the power at a particular customer site.
[0061] The disconnect switch 70 can be of conventional construction
in that it includes two switchable contacts, which are adapted to
be respectively connected between one line and one load blade
terminal, such as blade terminals 54 and 58 and 56 and 60.
[0062] To this end, the disconnect switch 70 is provided with a
pair of line terminals 72 and 74 which project outwardly from one
side of the housing of the disconnect switch 70 and a pair of load
terminals 76 and 78 which project from an opposite edge or surface
on the disconnect switch 70. The terminals 72 and 74 are adapted to
be disposed in registry with the load blade terminals 54 and 56
extending through the base wall 42. Suitable fasteners, such as
rivets, are employed to securely and electrically connect the
terminals 72 and 74 to the load blade terminals 54 and 56,
respectively. Likewise, the load terminals 74 and 78 are disposed
in proximity with the load blade terminals 58 and 60 and are
secured thereto by means of suitable fasteners as described above.
In this manner, the disconnect switch 70 can be easily mounted in
the base 42 without interfering with the circuit board 66.
[0063] Although the disconnect switch blade terminals 72, 74, 76
and 78 have been described as being separate from the blade
terminals 54, 56, 58 and 60 in the base 40, it will be understood
that the disconnect terminals 72, 74, 76 and 78 can be integrally
formed as a one piece, unitary structure with the blade terminals
54, 56, 58 and 60 to form a generally L-shaped blade terminal
projecting from the disconnect switch 70 which has an end portion,
similar to the blade terminals 54, 56, 58 and 60, which is
slidingly engagable through one of the apertures in the base wall
42.
[0064] FIG. 11 depicts the control circuitry for the disconnect
switch 70 which is mounted on a circuit board attached to the
bottom surface of the circuit board 66 facing the disconnect switch
70. The disconnect switch control circuitry includes a pair of
flip-flops which remember the state of an internal relay in the
disconnect switch 70. The flip-flops enable the disconnect switch
70 contacts to be switched to the last state after power is
reapplied to the remote unit 34 after a power interruption, removal
of the remote unit 34 from the meter socket 30, etc.
[0065] The disconnect switch 70 may be controlled by a signal from
the central site 10 to either "on" or "off" states as dictated by
the electric utility. The signal will be received by the circuit
and cause the flip-flops to switch states in accordance with the on
or off signal. At the same time, a push button 71, shown in FIG.
11, is mounted at a convenient location on the shell 44 and the
base 42 to enable a customer, after receiving appropriate
instructions from the electric utility, to manually reset the
disconnect switch 70 to the "on" state.
Remote Unit Circuitry
[0066] A general block diagram and the circuitry of the major
components of the remote unit 34 which are mounted in the base 40
at each utility customer site 18 is shown in FIGS. 7, 8A-8D and 19.
The circuit includes a power supply 122, voltage and current
sensing circuit, an analog to digital conversion circuit 124, a
central processing unit and associated logic 126, memories 128 and
129, a telephone communication modem 130, an opto-communication
port 254, and a clock. The details of these major components will
now be described.
[0067] As is conventional, the electrical power distribution
network 16 from the central utility company generating site
typically carries 240 VAC. A single-phase, three-wire power
distribution network 16 is shown in FIGS. 1 and 2 with three wires
connected to the electrical power distribution network 16 at each
utility customer site 18. Each line 134 and 136 carries 120 VAC RMS
with respect to neutral or ground wire.
[0068] The power supply 122, shown in FIG. 8C, provides regulated,
low level DC power at the preferred .+-.DC levels required by the
electronic components used in the circuit 120.
[0069] The circuit 120 also includes a voltage sensing network
denoted in general by reference number 180 in FIG. 8A. The voltage
sensing network receives 120 VAC RMS 60 Hz input from the utility
lines. One set of voltage inputs including voltage lead line
connections 182 and 183 are between one lead line and neutral;
while the other pair of inputs 184 and 183 is between the other
lead line conductor and neutral. The voltage lead 182 is input to a
combination of series connected, differential amplifiers 185, 186
which have a settable gain of 1/100, for example. The output of the
differential amplifiers is input to an A/D converter 124. The other
line connection 184 is input to a similar combination of
differential amplifiers thereby resulting in two separate voltage
inputs as shown by reference numbers 190 and 191 in FIG. 8A which
are connected to other inputs of the A/D converter 124. The
differential amplifiers 186 provide an instantaneous voltage
corresponding to the lead line voltage present on the conductors
182, 183 and 184 which is within the input range of the A/D
converter 124. It should be understood that the input voltages
supplied to the A/D converter 124 are instantaneous voltages.
[0070] The current sensing network of the circuit 120 includes
first and second current transformers 200 and 202, respectively, as
shown in FIGS. 3-5. The current transformers 200 and 202 each
include a high permeability toroid which is disposed around a
circular wall 199 surrounding each of the line blade terminals 54
and 56, respectively, in the base 40. The circular wall 199 is
preferably a continuous or discontinuous annular member or members
which are fixedly disposed on the base 40. Preferably, the wall 199
is integrally formed with and extends from the plane of the base
40.
[0071] The walls 199 provide a center support for the toroidal
current transformers 200 and 202 to fixedly mount the current
transformers 200 and 202 on the base 40. This fixes the position of
the current transformers 200 and 202 with respect to the inner
disposed blade terminals 54 and 56, respectively. Once the meter is
calibrated, the magnetic flux between of the current transformers
200 and 202 and the current flowing through the blade terminals 54
and 56 remains fixed thereby increasing the accuracy of the
electric power measurement of the meter as compared to prior art
automatic meter reader devices in which the current transformers
are not held in a fixed position and are capable of movement with
respect to the blade terminals.
[0072] The current transformers 200 and 202 are precision,
temperature stable transformers which provide a .+-.10 volt output
voltage signal in proportion to the instantaneous current flowing
through the line conductor. The electrical conductive coil of each
current transformer 200 and 202 maybe covered by a protective
insulating coating, with the conductive coil leads or outputs
extending therefrom.
[0073] The outputs 201 from the current transformer 200 are input
through a conditioning circuit to an amplifier 206. The output of
the differential amplifier 206, which represents the scaled
instantaneous current in the line conductor 134, is supplied as an
input to the A/D converter 124 as shown in FIG. 8A.
[0074] A similar signal conditioning circuit is provided for the
current transformer 202. The output leads 203 from the current
transformer 202 are supplied to a differential amplifier 211. The
output of the differential amplifier 211 is also supplied as a
separate input to the A/D converter 124.
[0075] The A/D converter 124 includes internal sample and hold
circuits to store continuous voltage and current signal
representations before transmitting such instantaneous voltage and
current representations to other portions of the circuit 120, as
described hereafter.
[0076] The twelve bit output from the A/D converter 124 is
connected to an electronic programmable logic device (EPLD) 127,
shown in FIG. 8A, which stores the instantaneous line voltages and
currents and performs at least an initial kilowatt hour (KwH)
calculation at the sample rate of the A/D converter 124 on each
link. This gives a real time, dual channel power measurement since
the power on each separate 120 VAC line and on the 240 VAC line is
separately calculated. This avoids the averaging employed in prior
power metering devices and provides greater power measurement
accuracy.
[0077] The individual line voltages and currents as well as the
calculated KwH are accumulated for a predetermined time period,
before the data is transmitted through a high speed data bus to a
central processing unit 126. The central processing unit 126, in a
preferred embodiment which will be described hereafter by way of
example only, is a 16 bit microcontroller, Model No. AMI86ES, sold
by Analog Devices. The microcontroller 126 executes a control
program stored in the flash memory 128, or backup EEPROM memory
129, as described hereafter, to control the operation of the
circuit 120. Clock signals from a real time clock circuit 127, in
FIG. 8B, are supplied to the processing unit 126 and other circuit
elements.
[0078] The microcontroller 126 also drives a display means 222,
such as a liquid crystal display, for consecutively displaying for
a brief time interval, for example, the total kilowatt hours (KwH)
total KVA total and KVA reactive, date, time, individual line
current and voltage, and average power factor. The display 222 can
be mounted, for example, at a suitable location on the circuit
board 66, for easy visibility through the transparent cover 57
mounted in the end wall of the shelf 44. The display 222, in a
preferred embodiment, contains 16 characters divided into
significant digits and decimal digits.
[0079] Referring now to FIGS. 9A and 9B, there is depicted a flow
diagram of the sequence of operation of the control program
executed by the CPU 126. After initialization, the CPU 126 executes
a number of steps to initialize various registers and to set up to
receive voltage and current data. Maintenance routines are also
executed to determine if any of the components, such as the
communication channels, the display 226, etc., need service. If any
maintenance or time event, such as a zero crossing of the voltage
or current waveforms is detected, the CPU 126 executes the detected
event step in a priority order from high to low as shown in FIG. 9B
which depicts an exemplary priority order of event processing.
Tamper Detection
[0080] The remote unit 34 of the present invention is provided with
a unique tamper detection circuit which not only detects at least
one or more different types of tamper events; but is capable of
recording the time of day and the total duration of the tamper
event as well as optionally taking action such as switching the
disconnect switch 70 to an open condition thereby preventing any
further application of electric power through the disconnect switch
70 to the customer site 18, 19 when the remote unit 34 is
reinserted into the socket 30.
[0081] The base 40 of the remote unit 34 is provided with at least
one and, preferably, two ground tabs 51, one being shown in FIG. 3,
which extend radially along the back surface of the base wall 42
into one of the notches 50 on the flange 48 surrounding the base
wall 42. Each ground tab 51 is positioned to engage a ground
connection in the socket 30 to complete a ground circuit from the
remote unit 34 through the socket 30 to earth ground.
[0082] The tamper detection sequence of the present invention is
based on the mounting relationship of the blade terminals 54, 56,
58 and 60 in the jaw contacts 32 in the socket 30 and the
connection between the ground tabs 51 and the mating ground tabs in
the socket 30. In addition, the voltage and currents of each of the
two legs or phases of power supply to a customer use site 18 as
well as the voltage and current of the center ground or neutral
connection are continuously monitored as part of the tamper
detection.
[0083] Since the blade terminals 54, 56, 58 and 60 extend a
distance, such as approximately 1/2 inch, into the jaw contacts 32
in the socket 30 when in the full mounted position shown in FIG. 5,
any attempt to remove the remote unit 34 from the socket 30 will
initially cause the ground tab 51 to separate from the mating
ground tab in the socket 30 in a timed sequence before the blade
terminals 54, 56, 58 and 60 completely separate from the respective
jaw contacts 32 and shown in FIGS. 15 and 16.
[0084] In a normal operating state when the remote unit 34 is
securely mounted in the socket 30, the voltage on the first and
second legs will equal approximately 120 VAC, and the voltage and
current on the ground leg will be zero. The current in the first
and second legs will be greater than zero.
[0085] During a tamper event when the remote unit 34 is initially
pulled from the socket 30, as shown in FIG. 15, the ground tab 51
will separate from the mating ground connection member in the
socket 30. At this time, the ground current will equal zero while
the voltage of the ground line will be greater than zero due to the
loss of ground connection. However, the blade terminals 54, 56, 58
and 60 are still connected to the socket jaw contacts 32 such that
current continues to flow through the first and second legs, i.e.,
i.sub.L1 and i.sub.L2>0. Continued separation of the remote unit
34 from the socket jaws 32 will eventually completely separate the
blade terminals 54, 56, 68 and 60 from the socket jaw contacts 32,
as shown in FIG. 16, such that the current flowing through the
first and second legs will drop to zero.
[0086] This defines the tamper signature detected by the remote
unit 34 of the present invention. Specifically, the tamper
signature is the detection of a time delay between the time that
the ground current equals zero and a ground voltage is greater than
zero and a subsequent time occurrence of at least one of the first
and second line and load currents equaling zero. In the case of a
power outage, the ground voltage will not be greater than zero, so
as to not constitute the tamper signature.
[0087] This sequence is depicted in FIG. 14. The microprocessor,
after detecting a tamper signature in step 127 will generate and
send a signal, labeled "tamper" in FIG. 8B, to the disconnect
switch 70 which will cause the disconnect switch 70 to switch or
remain in an open position the next time electric power is supplied
to the disconnect switch 70 through the blade terminals. This
signal is shown by reference number 129. The CPU 126 also generates
a notification signal 131 which can be transmitted back to the
central site 10 to indicated to the utility that a tamper event has
occurred. If the utility company chooses to contact the customer at
the customer site at which a tamper event was detected, the utility
company can notify the customer that tampering has been detected
and provide the customer with the time of the start of the tamper
detection as well as the total duration of the tamper event.
Corrective action can now be easily taken by the utility to address
the tamper event.
[0088] Upon reconnecting power to the offending customer site, the
central site 10 can send a signal through the communication network
described hereafter, to the customer site to set up the disconnect
switch circuitry to reapply power to the disconnect switch 70 after
the customer pushes pushbutton 71 on the remote unit 34. This will
cause the disconnect switch 70 contacts to switch to the closed
state thereby reconnecting a circuit between the line and load
blade terminals in the remote unit 34.
[0089] The signal 131 also contains data relating to the time and
date of the start of the detected tamper signature event as well as
the time duration of the tamper event. The time and date of the
start of the tamper event as well as the duration of the each
detected tamper event can be stored in the memory of the remote
unit 34 for later transmission to the central site 10 for tamper
event recordation, analysis, etc.
[0090] Instead of a control program consisting of software
instructions executed by a microprocessor, the above described
tamper event detection method can also be implemented in a
dedicated electronic circuit formed of electric current and voltage
sensors and logic elements which can sense the line and ground
circuit voltages and currents as well as a time separation between
certain voltages and currents as described above. The outputs of
such a circuit can be the "tamper" signal which can be transmitted
by various means, such as power line communication, Rf
communication, etc., to a central site 10. The "tamper" signal can
be applied directly to the disconnect switch 70 to automatically
disconnect the supply of electric power to the meter site at which
a tamper event has been detected.
[0091] In FIG. 18, the remote unit 34 of the present invention is
shown mounted in a ringless style watthour meter socket 400 which
includes a housing 402 and a cover 404. A raised annulus 406 is
formed in the cover 404 surrounding an aperture 408 through which
the sidewall of the remote unit 34 extends.
[0092] Inner disposed mounting brackets 410 and 412, which are
fixedly mounted on the sidewalls of the socket housing 402, extend
inward to an inner flange end 414. The inner flange end 414 is
positioned to engage one of the ground tabs 51 extending radially
outward on opposite diametric sides of the housing of the remote
unit 34. This completes a ground circuit through the internal
circuitry of the remote unit 34 and the earth ground connection in
the meter socket 400.
[0093] The tamper event signature detection method and apparatus
according to the present invention takes place in the same manner
as that described above.
Remote Communications
[0094] A first communication feature of the remote unit 34 of the
present invention is uninterruptible telephone service to the
customer site 18. The remote unit 34 intercepts calls by TCP/IP
modem interface circuitry that permits the remote unit 34 to answer
incoming calls from the central site 40 without detection by the
customer, and, additionally, a courtesy transfer feature that
automatically disconnects the remote unit 34 from the telephone
line and prepares the remote unit 34 for a later retry when the
customer picks up the handset on the telephone during a
communication between the remote unit 34 and the central site
10
[0095] The uninterruptible telephone service is achieved by
connecting the TCP/IP modem interface circuit in series in the
telephone(s) of the use site 18. In this manner, the remote unit 34
can recognize and intercept the ring circuit to receive or transmit
data to the central site 10.
[0096] Initially, the CPU 126 detects a voltage rise before a
voltage peak is reached in the ring circuit. The CPU 126 is
programmed to recognize the TCP/IP data format from the central
site 10. Upon detecting the TCP/IP format, the CPU 126 routes the
incoming telephone call to the appropriate part of the remote unit
circuitry 120 for processing and prevents the incoming call from
reaching the customer's telephone thereby preventing ringing of the
customer's telephone.
[0097] At the same time, the CPU 126 monitoring the ring circuit
for a voltage drop which occurs when the customer picks up the
handset of one of its telephones. Upon detecting the voltage drop,
the CPU 126 immediately disconnects the telephone ring connection
through the modem 130 and switches the connection to the customer's
telephone thereby allowing the customer to make an outgoing call
without interruption from the remote unit 34.
[0098] Referring now to FIG. 18, there is depicted the control
program sequence for operation of the remote communication
interface to the remote unit 34 and telephone service to the
customer site 18.
[0099] As shown in FIGS. 1 and 8D, the customer site 18 is provided
with a switch 300 which is embodied internally within a
programmable modem circuit 302 shown in FIG. 8D. The programmable
modem 302 executes a firmware control program which maintains the
switch 300 in the normally closed position for normal telephone
communication on the telephone network conductors to and from the
customer's telephone(s) 304.
[0100] As shown in FIG. 8B, the tip and ring conductors of the
telephone network are connected to a header or jack 306 which
provides input connections to the modem 302 as shown in FIG. 8D.
The switch 300, shown in a pictorial representation in FIG. 1, is
normally closed thereby providing a connection of the tip and ring
circuits on leads 308 to the customer's telephone 304. This is
embodied in control step 310 in FIG. 18.
[0101] The modem 302 is programmed to continuously monitor the ring
voltage in step 312 to detect a voltage rise from the nominal ring
voltage associated with a non-call condition. Such a voltage rise
is an indication of an incoming telephone call on the ring
conductor. Upon detecting a voltage rise in the ring conductor or
circuit in step 314, the modem 302 then looks at the following data
signals to detect a communication signal header format indicating a
data communication signal from the central site 10. As noted above,
this communication format can be the standard Internet TCP/IP
communication protocol.
[0102] If the data communication header format is not detected in
step 316 following a detection of a voltage rise in step 314, the
modem 302 maintains the switch 300 in a closed position as shown in
step 318 thereby allowing the normal incoming telephone call to be
connected to the customer's telephone 304. This allows the customer
to conduct a normal two-way telephone call without interference
from the remote unit 34.
[0103] Alternately, if the modem 302 detects the data communication
header format in step 316, the modem 302 opens the switch 300 in
step 320 and establishes data communication between the central
site 10 and the remote unit 34 in step 322.
[0104] The modem 302 continuously monitors the bidirectional data
communication in step 324 to determine when the data communication
is completed or finished. Upon completion of the data communication
exchange, the modem 302 will reclose the switch 300 in step
326.
[0105] As shown in FIG. 18, continuously during the data
communication sequence, the modem 302 monitors the ring voltage
which has previously risen to a voltage peak during a telephone or
data communication. If the customer picks up the handset of the
telephone 304 during the data communication sequence, the ring
voltage will drop. The modem 302, by continuously monitoring the
ring voltage in step 330 will detect the voltage drop from the
voltage peak in step 332. Immediately upon detecting a voltage drop
in step 332, the modem 302 terminates the data communication
between the remote unit 34 and the central site 10 in step 334 and
recloses the switch 300 in step 326 to enable the customer to
complete the telephone call.
[0106] The remote unit CPU will store a flag indicating that data
communication was interrupted and will restart or reconnect the
remote unit 34 with the central site at a later time or date to
complete the data communication sequence which was interrupted.
[0107] The same non-interruptible telephone service to the customer
also applies when the processing unit 126 initiates a data
communication to the central site 10. The modem 302 will initiate a
telephone call which will drive the ring voltage to a high voltage
level. The processor in the modem 302 will continuously monitor the
ring voltage during the data communication to and from the central
site 10 to detect a voltage drop which will occur if the customer
picks up the handset of the telephone 304. In a manner similar to
steps 330, 332, 334, and 336 in FIG. 18 and described above, the
processor in the modem 302 will immediately terminate data
communication and reclose the switch 300 to enable the customer to
complete a telephone call in a normal, non-interrupted manner. The
processor of the modem 302 can supply a signal or flag to the
processor 126 in the automatic meter reader 34 to indicate that
data communication was interrupted. The automatic meter reader 34
will, at a later program time, reinitiate data communication to the
central unit to retransmit all stored power values.
[0108] Another communication feature is the use of global network
communications via TCP/IP protocol through the modem 302. This
enables each remote customer site 18, 19, etc., to exchange data
with the central utility site 10 over a global network, such as the
Internet 21, in digitally encoded TCP/IP protocol at random time
based intervals. The communication is two-way frequency
programmable as well as duration programmable to permit
communication flexibility. Each reader 34 will have an Internet
address for unique communication with the central site 10.
[0109] The modem 302 at each customer use site as well as the modem
in the central site 10 provides one way of connection to a global
telecommunication network, such as the Internet or World Wide Web.
It will be understood that other interfaces or connections to the
global telecommunication network may also be employed, such as a
direct cable connection, direct subscriber line connection,
etc.
[0110] Another communication feature is wireless communication via
a cordless or wireless optical communications port 254. An optical
receiver, preferably an infrared receiver (IR) in the form of a
pair of photodiodes or LED's 257 is mounted on the circuit board 66
and has a field of view through transparent cover 57 to receive
optical or infrared signals from a wireless infrared programmer,
not shown. The infrared programmer can be a hand held unit,
computer lap top, or computer integrated infrared wand having an IR
transmitter to enable a utility service person to program, upload
and download information, connect and disconnect service via the
disconnect switch 70, and instantaneously obtain customer load
profile, use and service interruption data.
[0111] The photodiodes 257 are mounted on an integrated circuit 256
which carries connections to the ASIC circuit 255 for controlling
the transmit and receive data communication through the photodiodes
257 at a clock rate established by a crystal oscillator 258 input
to the ASIC circuit 255. Input and output leads are connected
between the ASIC circuit 255 and the central processor 126. The CPU
126, under stored program control, is capable of receiving and
decoding input signals received by the photodiodes 257 as well as
transmitting data in the desired format through one of the
photodiodes 257 to the external programmer.
[0112] The unique wireless communications port simplifies the
construction of the remote unit 34 since a plug connection to an
external programmer, as previously required, is no longer
necessary.
Out-Of-Spec Power
[0113] As described above, an electric utility is required to
deliver electrical power, particularly the voltage of such power,
within a specified range of maximum and/or minimum voltages. For
example, the supplied voltage cannot exceed 120 VAC RMS or be below
114 VAC RMS.
[0114] FIG. 12 depicts an exemplary voltage versus time waveform of
electrical power supplied to customer site 18. TOD1 depicts the
start of an out of range voltage excursion on leg or phase one of
the electric power delivered to the customer use site 18. The
remote unit 34 detects the out of range excursion of the
instantaneous voltage on leg one beyond the high voltage limit, and
stores the time of day (TOD1) of the beginning of the out-of-spec
voltage excursion as well as of the duration 301, or the total
length of time that the voltage is out-of-spec. This time duration
is converted to kilowatt hours in real time as shown in FIG. 13 to
provide an indication of the amount of out-of-spec power which was
delivered to a particular use site.
[0115] FIG. 12 also depicts a low voltage out-of-spec excursion.
The start time TOD2 and the duration 303 of this excursion are also
detected and stored in the memory of the remote unit 34 and the
kilowatt hours of low "out-of-spec" voltage is determined. In this
manner, a utility can determine whether or not electric power was
delivered to a particular use site outside of the required
range.
[0116] As shown in FIG. 13, when a upper RMS voltage limit is
exceeded on any of the lines in step 305, the CPU 126 monitors the
RMS voltage for the duration of the upper limit excursion in step
306. The CPU 126 via the EPLD 27 calculates the "out-of-spec"
energy use during the upper limit excursion in step 308. This
"out-of-spec" energy use is accumulated in kilowatt hours in real
time in step 310. A similar sequence is used when the lower voltage
RMS limit is exceeded in step 312. As described above, the CPU 126
monitors the RMS voltage during the lower limit excursion in step
314 and calculates the total "out-of-spec" energy use in kilowatts
below the legal voltage limit in step 316. The out-of-spec low
voltage and kilowatt hours are accumulated in real time in step 318
for transmission to the cental site 10 for billing purposes.
Power Demand Windows
[0117] As describe above, the CPU 126 through the voltage and
current detection circuitry 120 is capable of measuring and storing
the instantaneous line voltages in the calculated KwH and other
electric power parameters at each sample of the A/D converter
124.
[0118] The CPU 126 operates on a demand window concept wherein each
24 hour day is divided into a plurality of intervals of any
predetermined duration, such as 15 minutes, 30 minutes, 45 minutes,
60 minutes, etc. In each interval, the total KwH, KAV, average
phase angle, and peak voltage and current variables are calculated
and stored in the memory 128. This data can be transmitted to the
central site at any time upon receipt of an interrogation signal
from the central site 10 or on a time sequence initiated by the
remote unit 34.
[0119] This interval arrangement allows peak voltage and current
excursions on any of the power lines at a customer site to be
detected and reported. Previously, the average of the voltage and
current supplied to a particular customer site were used thereby
rendering the central utility incapable of detecting any peak
voltages or currents.
[0120] As shown in FIG. 10, in order to provide different real time
pricing for peak utility demand periods, week days, weekends,
holidays, etc., the control program of the CPU 126 is provided with
a plurality of discrete schedules, such as sixteen schedules by
example only. Three of the schedules are shown in FIG. 10, again by
example. The first schedule provides for regular time (non-daylight
savings time) wherein the power usage data is stored and
transmitted on a weekly basis. As shown in step 400, the weekly
data storage can also be subdivided into two different day
schedules, one for week days and one for weekends. Up to twenty
four windows per day are provided for each day schedule. At the end
of any day schedule time period, the CPU 126 automatically switches
to the other day schedule.
[0121] Similarly, the CPU 126 is programmed to automatically switch
to a daylight savings time schedule as shown in step 402. This can
also be on a weekly recurring data reporting basis. This schedule
is divided into three days schedules, by example only, covering the
weekdays, (Monday-Friday), a separate Saturday schedule and a
separate Sunday schedule. Each day schedule is subdivided into
twenty four windows per day, with the sequence automatically
switching to the next sequential day schedule at the completion of
the then current day schedule.
[0122] Finally, a holiday schedule is depicted in step 404 which is
provided on a daily basis.
* * * * *