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BACKGROUND OF THE INVENTION
An important problem facing the country is the increased demand for
electrical power. For the most part, electrical utilities have relied on
volunteer cooperation from individuals and industry to reduce power
consumption. However, with the capacities of power generating facilities
being more frequently strained to the point of causing occasional
"brown-outs," substantial attention has been given to ways of reducing
electrical demand.
Electrical rates based on peak demand are common in industry. If the peak
demand can be reduced by diverting some energy requirements to non-peak
hours, a considerable savings on electrical bills can be realized. There
have been a number of proposals to also place households on peak demand
rates. This would give the home owner an incentive to control his power
consumption provided he is supplied with a device which will indicate to
him when a peak demand period is being experienced.
Another possibility for reducing peak demand period consumption is to
remotely control the operation of energy consuming devices both in
industry and in the home.
With either of the foregoing approaches, it is necessary to provide a
communication system between the utility which monitors the total power
consumption and the customers. Several attempts have been made in the past
to accomplish this. Such efforts are summarized in an article entitled
"Creative Electric Load Management" by Thomas Laaspere and Alvin O.
Converse, appearing in the February, 1975 issue of IEEE SPECTRUM, pp.
46-50. Basically, these previous approaches have
a. used the transmission and distribution lines as the transmission medium;
or
b. employed only radio communication.
With respect to transmission line systems, the use of low frequency signals
on the lines requires a great amount of power to successfully transmit.
When higher frequency carriers are employed, substantial transmission line
losses are experienced.
With a radio system, a separate receiver is required at each remote
location, and this is an extremely expensive undertaking. Furthermore,
reception tends to be unreliable since the receivers are often located in
low lying areas, near reflectors, etc.
SUMMARY OF THE INVENTION
The present invention overcomes the shortcomings of previously known
electrical load management systems. More particularly, the difficulties in
utilizing transmission lines as the communication medium are avoided by
employing a radio network from the utility to pole-mounted distribution
transformers where radio receivers are located. The receivers are
selectively addressed by the coded signal which is transmitted. The
receivers are connected to distribution lines from the secondary side of
the distribution transformers by circuitry which impresses carrier signals
on the lines. Thus, command information is directed to those customers
associated with the addressed receivers in order to provide the users with
load status data and/or to control the operation of the users' power
consumption devices and electric meter.
Details of the invention now will be presented in the following description
and in the accompanying drawings wherein:
FIG. 1 is a block diagram of the overall electrical load management system;
FIG. 2 is a block diagram of a radio receiver and associated circuitry for
processing radio transmitted information and applying information to
distribution lines for carrier transmission;
FIG. 3 is a block diagram of circuitry for processing the carrier
transmitted information to actuate a user's display unit;
FIG. 4 is a block diagram of circuitry for processing the carrier
transmitted information to control a user's meter rate;
FIG. 5 is a block diagram of circuitry for processing the carrier
transmitted information to control a user's power consumption unit; and
FIG. 6 is a block diagram illustrating further details of the override
logic and monitor shown in FIG. 5.
DETAILS OF THE INVENTION
Referring first to FIG. 1, the overall electrical load management system is
illustrated. A radio transmitter centrally located at the power utility
sends load information in the form of coded signals to its customers.
Since the customers may be of different classes (e.g., industrial users
and homeowners), communities located in different areas, etc., the
receivers are shown as being arranged in groups. Under certain
circumstances, it may be desirable to communicate only with the customers
associated with a particular group, e.g., Group I. In such a case, the
receivers RA-1, RA-2 and RA-3 would respond to address information in the
transmitted signal (in a manner hereinafter to be described), while the
receivers of Group II would not respond. Thus, the customers of Group I
would receive load information in the form of carrier signals transmitted
over respective distribution lines generally designated by the numeral 10.
The radio receivers are mounted on poles in proximity to associated
distribution transformers. Each transformer couples an electrical power
line joined to its primary winding to distribution lines connected to its
secondary winding for stepping down the voltage level of the power carried
by the associated power line to a level to be supplied via the
distribution lines to a group of electricity users. Since each of the
distribution transformers services a number of customers, the expense of a
separate receiver for each customer is avoided. Additionally, with the
receivers mounted on poles, radio transmission from the utility is
reliable.
FIG. 2 illustrates the circuitry by which the radio transmitted information
is received and is then coupled to the distribution lines 10 as a
modulated carrier.
The coded signal which is transmitted from the central location comprises a
radio frequency carrier which is modulated by tone bursts. Modulation by a
tone burst of one frequency is representative of a binary "1," while
modulation by a second tone represents a binary "0." For purposes of
illustration, it will be assumed that each transmitted message contains
ten tone bursts. For reasons which will hereinafter become apparent, the
first and seventh tones will be the frequency representing the binary "1."
The coded radio transmitted signal is sensed by each of the receivers of
the system. These receivers are conventional FM units. For convenience,
only a portion of one unit is illustrated in FIG. 2 commencing with its IF
stage. The intermediate frequency modulated signal is applied to a
frequency demodulator which is provided with a conventional phase lock
loop. When the receiver is silent, there is no output on line 12 from the
phase lock loop. However, when a signal is being demodulated, line 12 is
active so as to permit a pair of conventional tone decoders 14 and 16 to
function. Decoder 14 responds to the modulating tone frequency F1
representative of the binary "1," while decoder 16 is responsive to
modulating tone frequency F2 which represents the binary "0". The output
of decoder 14 is applied to a one shot multivibrator 18 and to the data
input line of a shift register 20. Decoder 16 also is joined to
multivibrator 18. Application of pulses to multivibrator 18, produces,
after a brief delay, clock pulses which are applied to the shift register
20 to shift its contents.
The shift register has a capacity of 10 bits. Accordingly, as each tone is
detected by the decoders, the register is shifted so that any binary "1's"
from decoder 14 are stored in proper position within the register. As
stated previously, the first and seventh bits of the received coded signal
are binary "1's." Thus, when the shift register is full, these "1's"
appear on the register stage output lines 22 and 24. It is apparent that
except when the register is full, one or both of lines 22 and 24 must have
a binary "0" output. The full condition of the register is used as now
will be described.
The coded signal sent from the central location contains 5 address bits and
3 command bits. When the register is full, the former appear on the
register stage output lines 26, while the command bits appear on output
lines 28. The binary "1" on line 22 operats an address decoder 30 to which
lines 26 are joined as inputs. The decoder 30 is a conventional
comparator. If the address bits correspond with the preset address of the
comparator, a binary "1" output appears on line 32 of the decoder 30.
Otherwise, no output is generated on line 32. The binary "1's" on lines 24
and 32 partially condition the gate network 34. The output of line 22 from
the shift register also is applied to a timing logic circuit which is
partially conditioned by the output on line 12 from the phase lock loop.
Thus, when the loop is operating to indicate reception of transmitted
information, the application of a binary "1" from line 22 or a signal on
either of lines 38 and 40 (indicating respectively that no address was
decoded by comparator 30 and that for some reason no binary "1" existed on
line 24 when the register was full) causes a delayed signal to appear at
the output line 42 of circuit 36 to partially enable gate network 34 and
then clear the shift register in preparation for the reception of further
transmitted information. If a binary "1" is on any of the lines 28 and the
gate network 34 is fully conditioned by signals on lines 24, 32 and 42,
the command information is passed by the gate network via respective lines
44 to one of the oscillators 46. These oscillators each operate at a
different frequency (e.g., 3 KHz, 4 KHz and 5 KHz), and the oscillator
outputs are connected via an amplifier 48 to a carrier frequency
oscillator 50 operating, for example, at a frequency of 200 KHz. The
operation of oscillator 50 is also controlled by a signal on line 52 from
the timing logic circuit 36 so that the oscillator does not continuously
operate. With oscillator 50 functioning and a tone being applied thereto
by one of the oscillators 46, a modulated carrier is generated which is
applied via a conventional amplifier 54 and coupling circuit 56 to
distribution lines 10 from the secondary side of the distribution
transformer 11 associated with the receiver shown in FIG. 2.
The manner by which the modulated carrier is used to inform a particular
customer of electrical demand is illustrated in FIG. 3. An input from one
of the distribution lines 10 associated with a given transformer is
capacitively coupled to an input amplifier 58 and thence to a FM
demodulator 60 where the carrier frequency is stripped leaving only the
modulating frequency supplied by one of the oscillators 46. This frequency
is amplified at 62 and is applied to the three tone detectors 64 each
responsive to a different frequency (Fa, Fb and Fc). For purposes of
discussion, it will be assumed that a command bit on one of the output
lines 28 from shift register 20 in FIG. 2 caused on oscillator 46 having a
frequency Fa to operate, representing a peak load condition. In such a
case, Fa would be detected by the corresponding tone detector, causing a
latch circuit 66A to function, which in turn, causes a red lamp in a
customer display unit to be illuminated to indicate a peak load condition.
Similarly, command bits on the other of shift register output lines 28
result in the response of the Fb and Fc tone detectors to actuate latches
66B and 66C, thereby respectively energizing an amber lamp to indicate an
impending change in demand or a green lamp representing the absence of a
peak demand. The outputs of the latches also are connected to a monostable
multivibrator 68 having an alarm 70 at its output. Thus, the visual
display is supplemented by a brief audible one indicating an actual or
impending change in demand. The length of the audible alarm is a function
of the time constant of multivibrator 68.
The latch circuits 66A-66C are conventional flip-flops which are controlled
and unlatched by the output of a delayed clock generator 72 having as
inputs the outputs of the tone detector 64. Each time a new tone is
detected, generator 72 functions to provide a signal to unlatch a
previously latched circuit.
With the customer being provided with information concerning the utility's
demand status, he can voluntarily adjust his power consumption to conserve
energy, and in the case where peak load rates are charged, he also is able
to reduce his electrical bill by avoiding usage during peak periods.
A circuit similar to that described with respect to FIG. 3 also can be used
by the utility to automatically charge the customer for peak period usage.
This is accomplished by employing at the customer's location a known type
of meter having changeable scales. Of course, in such a system a
transition between scales occurs only when a peak demand period begins or
ends. Thus, the three tone detectors of FIG. 3 are not necessary.
Referring to FIG. 4, elements 58', 60' and 62' correspond to the circuits
58, 60 and 62 previously described. Two tone detectors are employed. These
include a first detector 64' for detecting tone Fa and a second detector
64" which has a band width wide enough to respond to tones Fb and Fc.
Operation of detector 64' in response to a peak demand energizes a latchh
66' causing in turn, relay driver 74 and relay 76 to function so as to
change the scale on meter 78 to that used during periods of peak demand.
The clock generator 72' is joined to the outputs of the tone detectors and
the input of latch 66' to operate in the same manner as previously
described with respect to FIG. 3. When the peak period passes, the circuit
66' unlatches causing de-energization of the relay driver which in turn
causes the relay to drop, thereby returning the meter to its normal scale.
A circuit of the type described with respect to FIG. 4 also may be used to
automatically control the operation of power consuming units at a
customer's location. Such an arrangement is illustrated in FIG. 5 with the
circuit being expanded to control three units (e.g., a clothes dryer, a
water heater and a central air conditioner). Like circuit elements are
identically identified in FIGS. 4 and 5, and further description of these
elements is unnecessary. The outputs of the latches 66' are connected via
override logic devices 80 and customer monitors 82 to the controlling
devices 84 for the units. When tone Fa is detected and the override logic
80 is inactive, the output signals from the latches 66'0 are passed to
devices 84 which typically are relay circuits for controlling the passage
of current to the power consuming units. Thus, with devices 84 energized,
power to the units is interrupted.
The override logic and monitors are provided to permit the customer to be
aware when a peak period is occurring and when during that period the
controlled unit is operative (or inoperative), and also to allow him to
override the automatic control commands. Such an arrangement is shown in
FIG. 6.
The override logic is merely an AND gate 86 which is partially conditioned
by a voltage from power supply 88 so as to pass the latch output. However,
a switch 90 is provided between the power supply and the gate 86. When
this switch is actuated to interrupt power supply to gate 86, no control
signals can pass the gate to shut off the customer's unit during peak
demand periods. A blue lamp 92 is associated with switch 90 to be
illuminated by the power supply when the circuit to gate 86 is
interrupted.
The customer monitor includes a monostable multivibrator 94 to which the
output of gate 86 is joined. During non-peak demand periods, an output
appears on one of the output lines 96 of the multivibrator to illuminate a
green light indicating the lack of peak demand. However, when gate 86
passes a signal representative of peak demand, an output is developed on
line 98 from the multivibrator causing a red lamp to illuminate,
indicating peak load. This output also energizes a timed switch 100 for
prescribing the timing of the control unit 84. An auxiliary red lamp is
joined to the output of switch 100 so that the customer is made aware of
those periods during peak demand when the controlled unit is actually shut
off.
The system which just has been described comprises an improved
communication arrangement for informing the customer of peak demand
periods. The system also permits the control of billing rates and the
supply of electricity to power consuming units during such periods. While
the foregoing constitutes a preferred embodiment of the invention, it will
be apparent that various circuit components, data arrangements and the
like may be employed to practice the invention.
While in the preferred embodiment of the invention the radio receivers are
described as being mounted on utility poles, it will be understood that
the receivers may be positioned at any other convenient location to permit
coupling to the secondary sides of the distribution transformers.
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