Load control system for standard electric utility meter

An automatic load control system for electric utility meters which includes an electric meter monitoring device which converts meter wheel revolutions into electronic digital pulses representing a known quantity of power consumption and a digital circuit which determines meter pulse rate or electric power demand and generates load control commands when predetermined demand levels are exceeded. Commands are transmitted from the monitoring device to a remote load control point by a data link to deactivate specific loads during periods of peak demand. Commands are also transmitted to selected remote locations for the purpose of switching indicator lights and alarms in order to display demand status to the power consumer.

RELATED APPLICATIONS 
The present application relates to generally similar subject matter 
disclosed in my co-pending application, Ser. No. 123,216, for Electric 
Meter Consumption Communicator concurrently filed herewith. 
BACKGROUND OF THE INVENTION 
1. Field of Invention 
This invention relates generally to a system which monitors data generated 
by an electric utility meter representing electrical power demand and is 
effective to generate commands to temporarily shut off predetermined 
electrical loads during peak demand periods. This invention provides a 
programmable means of limiting peak demand along with biofeedback 
indicators displaying the demand state directly to the electric power 
consumer. 
2. Description of Prior Art 
For energy conservation and potential reduction in consumer utility bills, 
many techniques have been proposed for automatically limiting peak demands 
for electrical power. Power demand exceeding the baseline generating 
capacity of a typical electric utility company requires utilization of 
inefficient peaking generators. Power demand falling below baseline 
capacity results in inefficient usage of generated power. Load control 
techniques provide a potential solution, smoothing the power demand curve 
to more efficiently match baseline generating capacity. 
Well-known technology presently exists affording control of desired loads 
for peak demand smoothing and some techniques have been implemented 
primarily for industrial customers. However, the prior art has yet to 
solve efficiently the problems of reliable demand monitoring and control 
cable installation in a manner acceptable to residential customers. Prior 
art systems include two general categories: centralized control systems, 
such as disclosed in U.S. Pat. No. 3,909,821 and decentralized or local 
control systems, as disclosed in U.S. Pat. No. 4,147,978. Central control 
systems monitor total demand at the generating facility. When a peak 
demand is anticipated, load control commands are generated and 
communicated to individually metered loads in order to deactivate all the 
predetermined loads (e.g., hot water heaters), in a general area. Although 
such an approach has technical merit, the primary disadvantage resides in 
a lack of consumer acceptance and high unit cost. The high cost of 
centralized systems affected by the cost of communicating load control 
commands to individual loads has precluded a large scale implementation. 
Local control systems must monitor power demand at the actual point of use, 
generate load commands when local demand peaks are detected, communicate 
the commands to the specific point of control and deactivate the desired 
load. Prior art systems typically monitor demand at the electric meter 
with a loop current probe which generates an analog signal proportional to 
the electric current flow. When the analog value reaches a predetermined 
threshold indicating a peak demand, load control command is generated and 
communicated to the control point either at the circuit breaker box or at 
the load by means of communication control cables. Although such systems 
are significantly more economical than centralized systems, local load 
control systems suffer from the disadvantage of poor accuracy inherent in 
low cost analog systems and high installation cost required for extending 
communication control cables to the point of control. In the case of some 
residential applications, installing cables through existing structures is 
not only cost prohibitive, but precludes consumer acceptance. Although 
automatic load control shows the potential for a vast contribution toward 
energy conservation, no single technique has been accepted for application 
on a large scale. 
SUMMARY OF THE INVENTION 
It is therefore a primary object of this invention to provide a low cost 
approach to load control and power demand limiting which avoids the 
installation of hardwire control cables and overcomes the aforementioned 
and other disadvantages and limitations. 
It is a further object of this invention to provide a highly reliable and 
accurate digital technique for local demand monitoring and load command 
generation. 
It is still a further object of this invention to provide optional command 
communication techniques including audio links, electro-optical links, 
radio frequency links and/or existing power line links which eliminate the 
requirement for the installation of communication control cables. 
It is still a further object of this invention to provide for load command 
receivers and switching units for each type of communication link 
providing for flexibility in installation and consumer acceptance. 
It is a still further object of this invention to provide consumer 
indicator lights using the aforementioned communication techniques to 
display an indication of demand state at a convenient location. 
It is a still further object of the present invention to overcome the 
technical limitations of prior art and specifically to provide a cost 
effective load control system incorporating highly accurate digital demand 
monitoring, data links for communicating load commands, and biofeedback 
indicators of demand state. 
According to the present invention, the foregoing and other objects are 
attained by providing an electro-optical meter wheel scanner device for 
generating digital pulses which represent known measures of electric power 
consumption, a digital circuit which determines the digital pulse rate or 
the power demand state and generates load commands, data links for 
communicating load commands and a command receiver means for switching 
specific loads on and off. 
The system according to the present invention utilizes a light 
emitter/detector pair mounted inside any standard electric meter to 
generate digital pulses proportional to the number of meter wheel 
revolutions. A digital circuit compares meter pulses to a time reference 
based on the power line frequency in order to determine demand. Upon 
detection of demand levels exceeding a predetermined digital value, a load 
control command is generated. Depending upon the particular geometry of a 
specific application, the load command is either coupled onto existing 
power lines in an established residence or are modulated onto audio, 
electro-optical or radio frequency carriers for through-the-air 
transmission to specific control points. An appropriate receiver at the 
control point detects the command and temporarily switches the load to a 
deactivated state for the duration of a demand peak. An identical 
technique is incorporated to transmit demand state signals from the meter 
to control indicator lights located at a convenient position so that the 
consumer can monitor his own demand. 
It is therefore an aspect of the present invention to provide an automatic 
load control system for an electric utility meter connected to a primary 
power source comprising a first arrangement to convert the primary power 
available from the utility meter into digital timing pulses and a source 
of secondary power for load control subsystems. A second arrangement 
powered by the secondary power monitors primary power consumption and 
generates a plurality of digital meter pulses with each pulse representing 
a predetermined quantity of primary power consumed. A third arrangement 
comprising a digital logic circuit, accepts the digital timing pulses and 
the digital meter pulses as inputs, determines the meter pulse rate, 
compares the pulse rate to a pre-set digital threshold, and generates a 
load control command when the threshold is exceeded. A fourth arrangement 
comprises a data link which transmits the load control commands to a 
remote control point without requiring installation of 
communication/control cables. Finally, the system includes a fifth 
arrangement comprising switching units located at the remote control 
point. This arrangement responds to the load control commands transmitted 
over the data link and provides preselected switching functions. 
Another aspect of the present invention resides in providing a system for 
limiting the rate of consumption of electricity in a circuit having a 
plurality of subcircuits and being measured by a utility meter, comprising 
a first arrangement which provides non-contact meter sensing, generates 
digital pulses in a proportional relationship to the quantity of 
electronic current flow and ascertains the rate of electricity 
consumption. A second arrangement comprises a data link which monitors the 
consumption rate and, when the rate exceeds a predetermined level, 
transmits a command signal to a control station and receives the 
transmitted command at the control station. A third arrangement comprising 
a load controller responds to commands from the data link and controls the 
flow of electric power to one or more of the subcircuits. 
For a better understanding of the present invention, together with other 
and further objects thereof, reference is had to the following description 
taken in connection with the accompanying drawings, and its scope will be 
pointed out in the appended claims.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to FIG. 1, the load control system for electric utility 
meters of the present invention comprises several major subsystems 
including a power supply 20, a meter scanner 33, a load control circuitry 
41, a load command transmitter 140, and a load command receiver 90. Each 
subsystem excluding the receiver 90 is constructed to be placed within the 
conventional confines of standard electrical watt hour meter 10. The 
digital load command 60 is transmitted utilizing selectively one of four 
transmitting media. The power supply 20, FIG. 1, converts an alternating 
current (AC) power 12 (typically 240 v AC, 60 Hz) available in the meter 
10 to two direct current (DC) outputs V1 25, V2 32 and to a fullwave 
rectified 120 Hz timing signal 21. The DC outputs V1 25, V2 32 power the 
digital circuitry 41 and the load command transmitter 140 respectively. 
The 120 Hz signal 21 is used as a time reference by the digital circuitry 
41 for timing meter pulse 41 rate. The meter scanner 33 incorporates a 
light emitter 35/detector 37 pair to monitor the meter wheel 11 and to 
produce discrete digital pulses 40 representing either full or half meter 
wheel revolutions. Meter pulses 40 are input to the load control digital 
circuitry 41 which determines if the pulse rate is above or below a 
preprogrammed digital value or threshold. A pulse rate above threshold 
generates a load control command 60 which activates the command 
transmitter 140. The "off" command signal is transmitted over one of four 
carriers 66, 67, 68, and 69. A load control receiver 90 recognizes the 
transmitted signal and either energizes a load switching unit deactivating 
the load switch 100 or switches demand indicator lights 101. After the 
digital circuitry 41 senses a meter pulse rate below threshold for a 
preprogrammed period of time, the "on" command is transmitted allowing the 
load control switch unit 100 to be reactivated and indicator lights 101 to 
be switched. 
POWER SUPPLY 
Referring now to FIG. 2, there is shown a load control power supply 20 
having as its input an AC power source 12, typically 240 volts AC at 60 
Hz, available within conventional electric meter 10. The input is applied 
to the primary coils 130 of a transformer 133 having two secondary coils 
131, 132, providing different voltage levels typically required for the 
load command transmitter 140 and the digital circuitry 41. The voltage 
present on one secondary coil 131 is rectified by a standard diode bridge 
D1 22 and is filtered by capacitor C1 23 in conjunction with a standard 
voltage regulator 24 to provide DC transmitter power V1 25. The output of 
the other secondary coil 132 is rectified by a fullwave rectifier bridge 
D2 26 providing a positive half sine wave signal at a frequency of 120 Hz, 
or double the power line frequency. Two resistors R1 27 and R2 28 are used 
as a voltage divider to provide a 120 Hz signal level 21 which is 
compatible with the digital electronics logic levels. The rectifier D2 26 
output current passes through diode D3 29 and is filtered by capacitor C2 
30 in conjunction with voltage regulator 31 to provide a source of DC 
power V2 32 for the digital electronics circuitry. 
METER WHEEL SCANNER 
The meter wheel scanner 33 is hereafter described in reference to FIGS. 3A 
and 3B. Essentially, every standard electric watt hour meter 10 includes 
an eddy current disk or meter wheel 11 which revolves at a rate 
proportional to current throughput. Therefore, each disk revolution or 
half revolution represents a specific quantity of metered power 
consumption. Anti-creep holes 13 in the disk 11 are also typical of 
standard electrical meters, since they are required to preclude disk 
revolution during power outages. The meter wheel scanner electro-optically 
monitors the passage of each hole 13 to produce the necessary meter pulses 
40 in a manner similar to the device shown in FIG. 5A of U.S. Pat. No. 
4,119,948 issued to the present applicant as co-inventor. The scanner 33 
includes a light emitting device 35 and a light detecting device 37. The 
emitting circuit comprises a current limiting resistor R1 34 in series 
with a light emitting diode (LED) 35 powered by supply voltage V2 32. The 
LED 35 emits a light 36 (typically 940 nanometers in wavelength) 
continuously. The detector circuit comprises an integrated detector 
diode/amplifier DET 37. A typical component of this type if the Feranti 
ZNP103 which combines a detector and an amplifier in a standard TO5 
component package. The integrated detector 37 is coupled to an external 
resistor R2 39 and capacitor C1 38 whose values determine the sensitivity 
of the detector 37. The detector circuit is also powered by supply voltage 
V2 32. The emitter and detector circuits are physically arranged to allow 
either transmissive detection, see FIG. 3A, or reflective detection, see 
FIG. 3B, of the anti-creep holes 13 in the disk 11. In either mode, the 
light input to the detector 37 is filtered with an optical band pass 
filter 14 whose center wavelength is that of the LED 35. In the reflective 
mode, the scanner 33 can also detect the passage of either reflective of 
absorptive radial stripes (not shown) on the disk. In the preferred 
embodiment, however, in the transmissive mode the emitter and detector 
components are positioned on opposite sides of the disk 11, so that 
passage of anti-creep holes 13 will allow light 36 from the emitter 
circuit to be transmitted to the detector circuit through the optical 
filter 14. In the reflective mode, the emitter and detector components are 
positioned on the same side of the disk 11 so that reflected light 36 is 
detected through optical filter 14 except when the anti-creep hole 13 
passes through the emitted beam 36. In either case, the detector circuit 
generates either a positive or negative logic digital pulse 40 for each 
hole 13 passage which represents a quantum measure of metered power 
consumption. 
LOAD CONTROL CIRCUIT 
The load control circuit 41 is a digital circuit which continuously 
monitors the rate of incoming meter pulses 40 to determine demand state 
which represents the rate at which electrical power is consumed in order 
to automatically generate digital load commands 60. The circuit 41 
comprises standard integrated circuit components and can be implemented 
either with discrete integrated circuits, with a single medium scale 
integrated circuit or with a microprocessor. The timing signal 21 
extracted from the power supply 20 passes through the digital inverter 43 
which shapes the signal for improved compatibility with the digital 
circuitry. The 120 Hz digital output from the inverter 43 is input to a 14 
stage ripple counter 44 with a maximum frequency dividing capability of 
divide by 16,384. The 2.sup.11 or divide by 2,048 output 45 is used as a 
time base reference. This output oscillates at one cycle per 17.1 seconds. 
The 2.sup.11 output 45 and the 2.sup.4 output 46 are used in conjunction 
with a standard RS bistable multi-vibrator 47 in order to generate a 
preset load command 49 for a four bit binary counter 42. This counter 42 
counts meter pulses 40 to a maximum of sixteen pulses prior to recycling. 
A thumbwheel binary coded decimal (BCD) switch 50 is used to preset the 
counter each time the load signal 49 is received. Since the counter 42 is 
preset every 17.1 seconds, the count at the end of each period represents 
the total number of meter pulses 40 received plus the preset, a measure of 
the actual demand. In this manner, the counter 42 is programmed for the 
desired demand threshold to count any discrete number of meter pulses 40 
between six and sixteen pulses prior to recycling. The carry or overflow 
output 52 of the counter 42 which is generated upon recycling is used as 
the basis for the load control command. The pulse output 52 is passed 
through inverter 53 and coupled by cable 54 to the "set" input of an RS 
bistable multi-vibrator 59. When the multi-vibrator goes to its "set" 
state, the "Q" output 60 goes from a logic zero state to a logic one state 
representing a deactivate load command. A second binary counter 55 is used 
to monitor the total time after the last high demand state was detected. 
The overflow signal 52 generated by counter 42 is coupled to the "clear" 
input of counter 55, so that the stored value in counter 55 will be set to 
zero each time a load command is generated. The input to counter 55 is the 
1/17.1 second pulse generated in counter 44. Therefore, counter 55 counts 
the total 17.1 second periods after each high demand state is detected. 
When the counter 44 attains the maximum value of 16 pulses or 4.6 minutes, 
it generates an overflow or carry signal 56 which is passed through 
inverter 57 and used to reset the multi-vibrator 59 causing the "Q" output 
to switch from a logic one state to a logic zero state representing an 
activate load command. 
Although the preferred embodiment of the load control circuit 41 is 
described, it will be obvious to one skilled in the art that additional 
counter and circuitry can be added to generate load control or indicator 
commands on any intermediate level of demand or to redefine the demand 
level or demand period. Due to its simplicity and therefore, low cost, the 
circuit 41 described represents the preferred embodiment for most 
applications. 
LOAD COMMAND COMMUNICATION LINKS 
The function of the present invention is not only to generate load control 
commands but to transmit commands to the point of switching either 
indicator lights or controlled loads without the necessity for running 
control cables. The load control commands 60 generated in the load control 
circuitry 41 are transmitted by any one of four means which serve this 
purpose as seen in FIG. 6 including a power line carrier means 66, similar 
to systems disclosed in U.S. Pat. Nos. 3,733,586, 3,719,928, and 
3,815,119; ultra-sonic means 67 and radio frequency means 69 similar to 
systems disclosed in U.S. Pat. No. 3,656,112; and electro-optical means 68 
similar to systems disclosed in U.S. Pat. No. 4,119,948. Although a vast 
number of techniques exist for encoding and decoding information 
transmitted on each type of carrier, simple, low cost oscillator encoding, 
discriminating filter decoding techniques are described in the preferred 
embodiment. 
The selective coding of load control commands is necessary especially in 
residential applications where two or more residences may be located in 
near proximity. In order to prevent a load control command generated at 
one metered residence from controlling loads or indicators located in an 
adjacent residence, each residence in near proximity must be assigned a 
specific control link code. Oscillator encoding seen in reference to FIG. 
5 is defined herein as selective frequency coding of load control commands 
which can take either of two forms: analog frequency coding or digital 
frequency shift keying. 
With reference to FIG. 5, analog frequency encoding converts the digital 
load command 60 to an assigned frequency signal to be modulated onto a 
carrier for load command transmission. Load command 60 directly activates 
oscillator 105 which outputs a signal 106 which oscillates at frequency 
F.sub.0. Signal 106 is modulated onto carrier 66, 67, 68, or 69 by 
transmitter 107. The transmitted signal is reconstructed by receiver 108 
to a signal 109 at frequency F.sub.O. The signal 109 is passed by an 
electronic band pass discriminating filter 110 and regenerated into the 
form of the original load command 111 which is used for directly switching 
loads and/or indicators. 
With further reference to FIG. 5, digital frequency encoding provides a 
more reliable means of coding load control commands. In this construction, 
load command 60 directly activates a digital encoder 112 which is designed 
to generate a specific digital word 113 in the form of a serial bit 
pattern. A digital word 113 directly activates a standard frequency shift 
keying (FSK) modulator 114. The FSK modulator 114 converts the input 
digital "one" bits to output frequency F.sub.1 and input digital "zero" 
bits to output frequency F.sub.2. The serial stream F.sub.1 and F.sub.2 
signals representing the digital word to be transmitted make up the FSK 
signal 115 which is modulated onto a carrier 66, 67, 68, or 69 by 
transmitter 116. The FSK signal 118 is reconstructed by receiver 117 and 
input to FSK demodulator 119. The FSK demodulator reconstructs the serial 
digital word 120 which is input to a digital decoder 121. The digital 
decoder 121 is designed to recognize the specific digital word 120 and, 
therefore, regenerate the original load command 122 which is used to 
directly switch loads and indicator lights. 
In order to provide the most cost effective load control system for the 
many various geometries encountered for decentralized load control in 
residences, industrial buildings, and commercial sites, four types of data 
links are provided in this invention. Each type of data link provides a 
low cost means for communicating load control commands over a short 
distance to the point of control. The preferred type of data link is 
strictly a function of the geometry and the environment encountered in 
each individual application. The four types of data links included are 
power line carrier, ultrasonic carrier, electro-optical carrier and 
radio-frequency carrier. It is anticipated that the power line carrier 
data link will be the preferred embodiment for the majority of 
applications. 
POWER LINE CARRIER 
As seen in FIG. 6, the load command signal 60 generated within the meter 10 
energizes an encoder 62 providing a coded signal which is induced on a 
coil 61 which loops around a primary power line 66. In this manner, a 
coded signal is induced on power line 66 and is distributed throughout the 
residence or metered building and is available at any existing power plug. 
A receiver module 90 along with its own power supply is simply plugged 
into any available power plug. The load switching unit 100 and/or 
indicator lights 101 are plugged into the receiver module 90. The receiver 
module 90 has two functions. First, a coil 70 looped around the primary 
power line 66 is effective to sense the coded signal when a load command 
60 is present. The detected signal is recognized by a decoder unit 91 to 
generate a load or indicator switch command 93. The switch command 93 
activates a switch either solid state or relay type which controls either 
indicator lights 101 displaying demand state or desired loads which are 
connected to load switching unit 100. Loads under control are deactivated 
during the period a load control command 60 exists and reactivated when 
the load control command 60 is terminated. 
ULTRASONIC CARRIER 
The ultrasonic carrier system 67 is essentially identical to the system 
described for the power line carrier 66 with the exception of the carrier 
medium. Since most load control applications require very short range 
links from the electric meter to the point of control, an ultrasonic data 
link is made feasible. In this construction, the encoder 62 output is 
induced onto a standard high frequency speaker 63 having transducers (not 
shown), which generate sound waves at corresponding frequencies. When a 
load command 60 is generated, ultrasonic waves 67 travel through the air 
at the speed of sound to a receiver 71 consisting of a high frequency 
microphone which converts the ultrasonic waves back into corresponding 
electronic signals. Identical circuitry provides for signal decoding and 
load/indicator switching as previously described. 
ELECTRO-OPTICAL CARRIER 
The electro-optical carrier system 68 is also essentially similar to those 
systems previously described except for the carrier medium. Where line of 
sight exists between the electric utility meter and the control point or 
intermediate repeater points, an electro-optical data link which transmits 
load control commands 60 through the glass meter cover 10 is made 
feasible. In this mode, the encoder 62 output is induced onto a DC current 
passing through a light emitting diode 64 or laser diode or other suitable 
optical transmitter to provide a modulated output beam 68. When a load 
command 60 exists, the modulated light beam 68 is transmitted to a photo 
detector 72 where the signal is converted to a corresponding electronic 
signal. Identical circuitry provides for signal decoding and 
load/indicator switching as previously described. 
RADIO-FREQUENCY CARRIER 
The radio-frequency carrier system 69 is also constructed similarly to the 
above described systems except for carrier medium. Since most load control 
applications require very short range command transmission from the meter 
10 to the switching point 90, a low power radio frequency data link is 
then made feasible. In this case, the encoder 62 output is induced onto a 
radio-frequency antenna 65 which radiates radio waves 69 at the same 
frequency. When a load command 60 exists, radio waves 69 are transmitted 
to a receiver antenna 73 which converts the electro-magnetic radiation 
back into electronic signals. Identical circuitry provides for decoding 
and load/indicator switching. 
While there have been described what are at present considered to be the 
preferred embodiments of this invention, it will be obvious to those 
skilled in the art that various changes and modifications may be made 
therein without departing from the invention and it is aimed, therefore, 
in the appended claims to cover all such changes and modifications as fall 
within the true spirit and scope of this invention.