Note: Descriptions are shown in the official language in which they were submitted.
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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-outsl~,
! substantial attention has been given to ways of reducing
electrical demand.
~lectrical rates based on peak demand are common
in industry. If the peak demand can be reduced by divert-
ing some energy requirements to non-peak hours, a consider-
able 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
încentive 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.
~nother possibility for reducing peak demand
period consumption is to remotely control the operation of
energy consuming devices both in industry and in the home.
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With either of the foregoing approaches, it is
necessary to provide a communication system between the
utllity 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 0. 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 trans-
mission line losses are experienced.
With a radio system, a separate receiver is required
at each remote location, and this is an extremely expensive
underta~ing. Furthermore, reception tends to be unreliable
since the receivers are often located in low lying areas,
near reflectors, etc.
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SUMMARY OF THE INVENTION
The present invention oyercomes 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 trans-
formers 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 which load
status data and/or to control the operation of the users'
power consumption devices and electric meter.
STATEMENT OF THE INVENTION
Thus, in accordance with one form of the invention, an
improved electrical load management system comprises a plural-
ity of distribution transformers each having primary and second-
ary windings, each of said transformers coupling an electrical
power line joined to its primary winding to distribution lines
connected to its secondary winding and stepping down the volt-
age level of the power carried by the associated power line
to a level to be supplied via the distribution lines
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to a group of electricity users, each distribution line ser~
vicing at least one of said users;
means for transmitting by radio ~rom a central location
a coded signal having address and command information;
a receiver located proximate each of said distribution
transformers for receiving said signal independently of said
power lines and the transformers;
means associated with said receivers for decoding said
signal;
means responsive to said decoded signal for generating
a modulated carrier signal; and
mea`ns for coupling said carrier signal via the dis-
tribution lines to at least one group of users determined by
the decoding of said address information.
Details of the invention now will be presented in the
following description and in the accompanying drawings
wherein:
FIGURE 1 is a block diagram of the overall electrical
load management system;
FIGURE 2 is a block diagram of a radio receiver and
associated circuit-y for processing radio transmitted
information and applying information to distribution lines
for carrier transmission;
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- FIGURE 3 is a block diagram of circuitry for
processing the carrier transmitted information to actuate
a user's display unit;
FIGURE 4 is a bloc~ diagram of circuitry for
processing the carrier transmitted information to control
a user's meter rate;
FIGURE 5 is a block diagram of circuitry for
10,
processing the carrier transmitted information to control
a user's power consumption unit; and
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FIGURE 6 is a bloc~ diagram illustrating further
details of the override logic and mo~itor shown in FIGURE 5.
DETAILS OF THE INVENTION
Referring first to Fiqure 1, the overall electrical
load management system is illustrated. A radio transmitter
centrally located at the power utility sends load informa-
tion 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 communi-
cate only with the customers associated with a particular
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group, e.~., Group I. In such a case, the receivers RA-l,
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 distribu-
tion 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 wind-
ing 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 dis-
tribution lines to a group of electricity users. Since each
of the distribution transformers services a number of cus-
tomers, 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.
Figure 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.
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The coded s~snal ~hich 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
S "1", while modulation by a second tone represents a
binary "o". For purposes of illustration, it will be ;
assumed that each transmltted message contains ten tone
bursts. For reasons which will hereinafter become appar-
ent, 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 Figure 2 commencing with its
, 15 ~ 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
2~ active so as to permit a pair of conventional tone decoders 14
and 16 to function. Decoder 14 responds to the modulating
tone frequency Fl representative of the binary "1", while
decoder 16 is responsive to modulating tone frequency F2
which represents the binary "o". 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 multi-
vibrator 18, produces, after a brief delay, clock pulses
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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 "l's" from
decoder 14 are stored in proper position within the register.
As stated previously, the first and seventh bits of the
recei~ed coded signal are binary "l's". Thus, when the
shift register is full, these "l's" appear on the register
1 10 stage output lines 22 and 24. ~t is apparent that except
¦ when the register is full, one or both of lines 22 and 24
must have a binary ~o~ output. The full condition of the
register is used as now will be described.
The coded signal sent from the central location con-
lS tains 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 operates 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 "l'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 con-
ditioned by the output on line 12 from the phase lock loop.
Thus, when the loop is operating to indicate reception of
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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 comparatcr 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 networ~ 34 is fully conditioned
by signals on lines 24, 32 and 42, the command information
is passed by the gate network ~ia respective lines 44 to
one of the oscillators 46. These oscillators each operate
at a different frequency (e.~., 3 KHz, 4KHz and 5XHz),
and the oscillator outputs are connected via an amplifier
48 to a carrier frequency oscillator 50 operating, for
example, at a frequency of 200KHz. The operation of oscil-
lator 50 is also controlled by a signa~ 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 dis-
tribution lines 10 from the secondary side of the distribu-
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tion transformer'associated with the receiver shown inFigure 2.
The manner by which the modulated carrier is used
to inform a particular customer of electrical demand is
illustrated in Figure ~. An input from one of the distribu-
tion lines lO associated with a given transformer is
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capacitiyely coupled to an input ~mplifier 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
responsi~e to a different frequency tF.a, 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 Figure 2 caused an oscillator 46 having a frequency Fa
¦ 10 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 con- -
stant 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
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- of the tone detectors 64. Each time a new tone is de-
tected, 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 volun-
tarily 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
Figure 3 also can be used by the utility to automatically
charge the customer for peak period usage. This is accomp-
lished 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 Figure 3 are not necessary.
Referring to Figure 4, elements 58', 60' and 62'
correspond to the circuits 58-, 60 and 62 previously des-
cribed. Two tone detectors are employed. These includea first detector 64' for detecting tone Fa and a second
detector 64'' which has a band width wide enough ta respond
to tones Fb and Fc. Operation of detector 64' in response
to a peak demand energizes a latch 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
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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 Figure 3. W~.en 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
Figure 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 Figure 5 with the
cixcuit 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 Figures
4 and 5, and ~urther description of these elements is un-
necessary. 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 out-
put signals from the latches 66' 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 inter-
rupted.
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
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is operative (or inoperative~, and also to allow him to
override the automatic control commands. Such an ar-
rangement is shown in Figure 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 multi-
vibrator 94 to which the output of gate 86 is joined. Dur-
ing 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 representati~e of peak demand,
an output is developed on line 98 from the multivibrator
2Q causing a red lamp to illuminate, indicating peak load.
This output also energizes a timed switch 100 for prescrib-
ing 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.
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The system which just has been described comprises
an improved communciation 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 in-
vention, it will be apparent that various circuit compon-
ents, data arrangements and the like may be employed to
practice the invehtion.
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 trans-
formers.
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