Field of the Invention
The present invention relates to an electric power
meter which separately measures the amount of electric power
for purchase and the amount of electric power for sale.
Background of the Invention
With the recent proliferation of private power
generation such as solar power generation, wind power
generation, it has been proposed that for example, direct
current (DC) power generated by photovoltaic power
generation is converted to alternating current (AC) power
by an inverter so that the converted AC power may be
consumed by a household. Further, it has also been proposed
that if the amount of the electric power generated by an
electricity generation system such as a photovoltaic power
station or the like exceeds the amount of the electric power
consumed by the household (excess electric power
generation), the excess electric power can be sold to a
power supply company. To this end, an electric power meter
for measuring the excess electric power for sale that is
generated by a photovoltaic power system is first connected
to a drop wire or service wire that is connected to the
network of electricity supply, so as to measure the amount

of electric power that flows to the electricity supply
network. Then, the amount of electric power for sale is
calculated based on the indications of the electric power
meter, and a charge corresponding to the calculated amount
of electric power is paid to a person (power seller) who
owns the photovoltaic power system.
Generally, the amount of electric power for purchase
or sale that is measured by an electric power meter for the
purchase or sale of electric power is sent to a measuring
center via a public data network by a remote-measurable
electric power meter that was disclosed e.g. in Patent
Document 1.
[Patent Document 1] Japanese Patent Application
Publication No. 2005-70869
Summary of the Invention
However, in order to obtain the amount of electric
power to be purchased together with the amount of electric
power to be sold, using such a remote-measurable electric
power meter, there is a need to provide in parallel a
dedicated electric power meter for measuring the amount of
electric power for purchase and another dedicated one for
electric power for sale. The amount of electric power for
purchase or sale is the power information of merely one
consumer, so that it is unreasonable for the electric power

meters for the purchase and sale of electric power to be
separately provided in order to obtain the power information
of the respective consumer, and if this is done, wiring
structures thereof essentially become complicated.
Accordingly, the present invention has been made
keeping in mind the above problems occurring in the related
art, and the present invention provides an electric power
meter that is capable of reasonably measuring a plurality of
pieces of power information about respective power
consumers, that is, information about the amount of electric
power for purchase or sale.
In accordance with an embodiment of the present
invention, there is provided an electric power meter
separately measuring an amount of electric power for
purchase supplied from an electric power system and an
amount of electric power for sale which is generated by an
electricity generation device, wherein the electric power
meter detects a power flow the electric power system and
separately measures the amount of electric power for
purchase and the amount of electric power for sale while
distinguishing between the amount of electric power for
purchase and the amount of electric power for sale on the
basis of a direction of the detected power flow.
With such configuration, the electric power meter
detects the flow of power in the electric power system and
distinguishes between the amount of electric power for

purchase and the amount of electric power for sale on the
basis of the detected flow of power, so that it can be
determined whether the electric power is power supplied from
an electricity supply company to a power consumer or vice
versa, based on the direction of flow of power input to the
electric power meter. Because of this, the amount of
electric power for purchase and the amount of electric power
for sale are separately measured based on that
determination, and the power information of respective power
consumers about the amount of electric power for purchase
and the amount of electric power for sale can be measured by
a single electric power meter. Thus, the plurality of
pieces of power information about respective power
consumers, such as the amount of electric power for purchase
and the amount of electric power for sale, can be reasonably
measured by a single electric power meter.
Further, the electric power meter may be provided with
a power display that displays the amount of electric power
for purchase and the amount of electric power for sale,
which were separately measured, in a discriminative manner.
With such configuration, the electric power meter is
provided with a display that, displays the amount of electric
power for purchase and that for sale, which were separately
measured, in a discriminative manner, when measuring the
amount of electric power for purchase and that for sale
using the unitary electric power meter, so that the unitary

electric power meter can display two kinds of information,
such as the amount of electric power for purchase and the
amount of electric power for sale, in a discriminative
manner. Thus, when configuring the unitary electric power
meter that is capable of measuring both the amount of
electric power for purchase and the amount of electric power
for sale, the practicality can be improved properly.
Further, the power display may include two separate
display units that consist of a display unit which displays
the amount of electric power for purchase and a display unit
which displays the amount of electric power for sale.
With such configuration, the power display includes
two separate display units that consist of a power display
unit for the amount of electric power for purchase and a
power display unit for the amount of electric power for
sale, the amount of electric power for purchase and the
amount of electric power for sale can be physically
distinguished between and separated. Thus, when configuring
the unitary electric power meter that is capable of
measuring both the amounts of electric power for purchase
and for sale, it is easier to discriminate between the
amount of electric power for purchase and that for sale.
Further, the power display may be composed of a single
display screen having a common display section on which both
the amount of electric power for purchase and the amount of
electric power for sale are displayed in common.

With such configuration, the power display is composed
of a single display screen having a common display section
on which both the amount of electric power for purchase and
the amount of electric power for sale are displayed in
common. Thus, when displaying both the amount of electric
power for purchase and the amount of electric power for sale
in a discriminative manner using the electric power meter,
the power display can be simplified.
Further, the common display section of the power
display may display the amount of electric power for
purchase and the amount of electric power for sale in a
time-division manner.
With such configuration, the common display section of
the power display displays both the amount of electric power
for purchase and the amount of electric power for sale in a
time-division manner. Thus, when displaying both the amount
of electric power for purchase and the amount of electric
power for sale on the common display section of the unitary
power display, respective integrating values can be easily
identified.
Further, the electric power meter may have a
communication function of automatically transmitting the
amount of electric power for purchase and the amount of
electric power for sale, which were separately measured, to
a measuring center that is a management center of the
electric power meter, in such a manner as to alternately

transmit information about both the amounts of electric
power for purchase and for sale to the measuring center in
sequence.
With such configuration, the amounts of electric power
for purchase and for sale, which were separately measured,
are alternately transmitted to the measuring center in
sequence, so that the electric power meter can transmit
respective power information including the amounts of
electric power for purchase and for sale to the measuring
center in a discriminative manner based on timing when the
respective power information is transmitted, while having a
single communication interface in common. Thus, when
configuring the remotely measurable electric power meter
that is capable of measuring both the amounts of electric
power for purchase and for sale, the amounts of electric
power for purchase and for sale for each power consumer can
be managed with high reliability. Further, when it is
configured such that the amounts of electric power for
purchase and sale, which were separately measured, are
alternately transmitted to the measuring center in sequence,
both instant information about the purchased power and about
sold power can be transmitted together to the measuring
center.
Further, the electric power meter has a communication
function of automatically transmitting the amount of
electric power for purchase and the amount of electric power

for sale, which were separately measured, to a measuring
center that is a management center of the electric power
meter, in such a manner as to selectively transmit to the
measuring center a measured amount of electric power
whenever determination is made whether the amount of
electric power is for purchase or for sale.
With such configuration, a target amount of electric
power to be measured is selectively transmitted to the
measuring center according to the determination of the
amounts of electric power for purchase and for sale, so that
the electric power meter can transmit to the measuring
center respective power information about the amounts of
electric power for purchase and for sale as a group of
separate power information, while sharing a single
communication interface.
Thus, when configuring the remotely measurable
electric power meter that is capable of measuring both the
amounts of electric power for purchase and for sale, the
amounts of electric power for purchase and for sale for each
power consumer can be managed with high reliability.
Further, when it is configured such that a target amount of
electric power is selectively transmitted to the measuring
center according to the determination of the amounts of
electric power for purchase and for sale, it is possible to
transmit at least that power information required for the
remote measuring to be performed, because only the electric

power information that is about the electric power to be
measured is transmitted to the measuring center.
Further, the communication function may be implemented
by power line communication wherein a power line is a
communication medium.
With such configuration, the communication function is
implemented via power line carrier communication, when the
power information measured by the electric power meter is
transmitted to the measuring center, there is no need to
provide a separate communication path, and it is possible to
secure a dedicated communication path using an existing
communication medium.
Further, the electric power meter may be a unit-type
electric power meter.
With such configuration, the electric power meter is a
unit-type electric power meter, so that it is possible to
modify the function of respective units constituting the
electric power meter by replacing them with another. Thus,
for example, it is possible to easily change the function of
a power display having a single display screen to that of a
power display having two separate display screens and vice-
versa when the respective unit is replaced with another.
Thus, the degree of freedom of the electric power meter can
be further improved upon.
According to the electric power meter of the present
invention, the plurality of pieces of power information

about the amount of electric power for purchase or sale for
respective power consumer can be reasonably measured by a
unitary electric power meter.
Brief Description of the Drawings
The objects and features of the present invention will
be apparent from the following description of embodiments
when taken in conjunction with the accompanying drawings, in
which:
Fig. 1 is a block diagram of the schematic
construction of a power supply system to which an electric
power meter of the invention is applied;
Fig. 2 is a diagrammatic view showing the schematic
construction of an electric power meter in accordance with a
first embodiment of the invention;
Fig. 3 is a view showing the display type of power
information using a power display used to display the amount
of electric power for purchase and a power display used to
display the amount of electric power for sale in accordance
with the first embodiment of the electric power meter;
Fig. 4 is a block diagram of the schematic view of the
electric power meter in accordance with the first
embodiment;
Fig. 5 is a time chart showing a power information
transmission procedure that uses the electric power meter in

accordance with the first embodiment;
Fig. 6 is a diagrammatic view showing the schematic
construction of an electric power meter in accordance with a
second embodiment of the present invention;
Fig. 7 is a time chart showing a procedure of
displaying the amount of electric power for purchase and
sale using the electric power meter in accordance with the
second embodiment;
Fig. 8A is a view showing a displayed example of the
amount of electric power for sale which is displayed on a
common power display, and Fig. 8B is a view showing an
example of displaying the amount of electric power for
purchase which is displayed on a common power display;
Fig. 9 is a diagrammatic view showing the schematic
construction of an electric power meter in accordance with a
third embodiment of the present invention; and
Fig. 10 is a block diagram showing the schematic
construction of the electric power meter in accordance with
the third embodiment.
Detailed Description of the Preferred Embodiments
Reference will now be made in greater detail to
exemplary embodiments of the invention with reference to the
accompanying drawings which constitute a portion of this
specification. The same reference numerals will be used

throughout the drawings and the description to refer to the
same or like parts, and overlapping descriptions thereof
will be omitted.
(First Embodiment)
A power supply system to which an electric power meter
of the present invention has been applied will now be
described with reference to Fig. 1.
As shown in Fig. 1, a house (which is a power
consumer) is provided with the power supply system 1 that
supplies electric power to a variety of household appliances
(lighting device, air conditioners, domestic appliances,
audio video device, and the like.). The power supply system
1 uses a power source, such as a household alternating-
current power supply (AC power source) 2 and a solar cell 3
that generates electricity by converting sunlight into
electricity, in order to operate the diverse appliances.
The power supply system 1 supplies electric power to a DC
device 5 that operates under DC power supplied from a DC
power supply (DC supply voltage) , as well as an AC device 6
that operates under AC power from a supply voltage (AC
supply voltage).
While the following embodiments have used a power
supply system 1 mounted in a house by way of example for the
sake of description, the present invention is not limited
thereto, but the power supply system may be mounted and
applied to a multi-residential house or apartment, the

office, a factory, or the like.
The power supply system 1 is provided with a cabinet
panel including a control unit 7 and a DC distribution
switchboard 8 (including a DC breaker). In addition, the
power supply system 1 is also provided with a controller 9
and a relay unit 10 to control the operation of the DC
device 5 of the house.
The control unit 7 connects with an AC distribution
switchboard 11 that distributes AC power, via an AC power
line 12. The control unit 7 connects to the power supply 2
via the AC distribution switchboard 11 and also to the solar
cell 3 via a DC power line 13. The control unit 7 receives
AC power and DC power from the AC distribution switchboard
11 and the solar cell 3, respectively, and converts them
into DC power to be the power source for an appliance. The
control unit 7 outputs the converted DC power to the DC
distribution switchboard 8 via a DC power line 14, or
otherwise to a condenser 16 via a DC power line 15 to store
the DC power therein.
It is also possible for the control unit 7 to receive
AC power from the AC distribution switchboard 11, and to
convert the power from the solar cell 3 or condenser 16 to
AC power and supply it to the AC distribution switchboard 11
as well. The control unit 7 performs data communications
with the DC distribution switchboard 8 via a signal line 17.
The DC distribution switchboard 8 is a kind of breaker

that disposes of DC power. The DC distribution switchboard
8 allows DC power input from the control unit 7 to split,
and outputs the split DC power to the controller 9 via a DC
power line 18, or otherwise to the relay unit 10 via a DC
power line 19. The DC distribution switchboard 8 performs
data communications with the controller 9 via a signal line
20, or otherwise with the relay unit 10 via a signal line
21.
The controller 9 is connected to a plurality of DC
devices 5. The DC devices 5 are connected with the
controller 9 via a DC supply line 22 which carries both the
DC power and data concurrently. The DC supply line 22
carries both the power and data to the DC device 5 via a
pair of wires using DC overlapping communications in which a
communications signal transmitting data with a high
frequency carrier wave overlaps with the DC power that is a
power source of the DC device. The controller 9 receives DC
power for the DC device 5 via the DC power line 18 and
checks the DC device 5 to be controlled and checks how to
control the corresponding DC device 5 based on an
operational command obtained via the signal line 20 from the
DC distribution switchboard 8. The controller 9 outputs the
DC power and operational command to the target DC device 5
via the DC supply line 22 to control the operation of the DC
device 5.
The controller 9 is connected, via the DC supply line

22, to a switch 23 that is operated to switch the operation
of the DC device 5. The controller 9 is connected, via the
DC supply line 22, with a sensor 24 which detects a signal
transmitted from, e.g., an infrared remote controller.
Thus, the DC device 5 is controlled by a communications
signal that flows over the DC supply line 22 by any of the
operation of the switch 23, the detection of the sensor 24,
as well as the operational command from the DC distribution
switchboard 8 .
The relay unit 10 is connected by separate DC power
lines 25 to the plurality of DC devices 5. The relay unit
10 receives DC power for the DC device 5 via the DC power
line 19 and checks the DC device 5 to be controlled based on
an operational command obtained via the signal line 21 from
the DC distribution switchboard 8. The relay unit 10 lets
through or breaks the power supply from a built-in relay to
the target DC device 5 via the DC power line 25 to control
the operation of the DC device 5. Further, the relay unit
10 is connected to a plurality of switches 26 to manually
control the DC device 5, so that the DC device 5 is
controlled by the ON/OFF operation of the relay with respect
to the power supply, which acts on the DC supply line 22 by
the manipulation of the switches 26.
The DC distribution switchboard 8 is connected to a DC
electric outlet 27 via a DC power line 28, wherein the DC
electric outlet can be attached to a house in the form of,

e.g., a wall outlet or bottom outlet. When a plug (not
shown) of the DC device is inserted into the DC electric
outlet 27, DC power can be directly supplied to the DC
device.
An electric power meter 50 is connected to an electric
power system located between the AC power supply 2 and the
AC distribution switchboard 11. Here, the electric power
meter 50 is capable of remotely measuring the amount of
electric power for purchase, i.e. the wattage of electric
power of the AC power supply 2, and the amount of excess
electric power for sale, i.e. excess wattage for sale of
electric power generated by the solar cell 3. The electric
power meter 50 transmits the results of the measuring to a
measuring center 100 that is a management center for the
power information and located in a power supply company or
the like, via, e.g., power line carrier communication or
wireless communication.
The power supply system 1 is provided with a network
system 30 that enables a variety of home appliances to be
controlled via network communication. The network system 30
is provided with a home server 31 which is the control unit
of the network system 30. The home server 31 is connected
to an external management server 32 via a network N such as
the Internet, and also with a home appliance 34 via a signal
line 33. The home server 31 operated under the DC power, as
a power source, obtained via a DC power line 35 from the DC

distribution switchboard 8.
The home server 31 is connected to a control box 36
via a signal line 37. The control box 36 manages the
operation control of diverse home appliances via network
communication and can be connected to the control unit 7 and
DC distribution switchboard 8 via the signal line 17, and
directly control the DC device 5 via a DC supply line 38.
The control box 36 is connected with e.g. a gas/water meter
39 that is capable of remotely measuring the amount of gas
or water that is used, and also with a manipulation panel 40
of the network system 30. The manipulation panel 40 is
connected to, e.g., a monitoring device 41 which includes a
door phone extension unit, a sensor, or a camera.
When an operational command for a variety of home
appliances is inputted via the network N, the home server 31
commands the control box 36 to operate the diverse
appliances in conformity with the operational command.
Further, the home server 31 can provide the management
server 32 via the network N with a variety of information
that is obtained from the gas/water meter 39. Further, when
the home server 31 receives that the monitoring device 41
detects an abnormality detection from the manipulation panel
40, the home server 31 also provides the management server
32 with the corresponding information via the network N.
According to the electric power supply system, driving
the variety of home appliances can be collectively managed

by the home server 31, and electric power can be effectively
supplied to the diverse appliances.
However, in order to remotely measure the amounts of
electric power for purchase and sale for each power
consumer, there is a need to provide in parallel a dedicated
electric power meter for measuring the amount of electric
power for purchase and another dedicated electric power
meter for measuring the amount of electric power for sale.
The amount of electric power for purchase or sale is the
power information of merely one power consumer, so that it
is unreasonable to separately provide the electric power
meters for purchase and sale in order to obtain the power
information of the respective consumer, and if this were the
case, the wiring structures thereof would have to be
complicated.
Thus, the present embodiment is configured to provide
only one electric power meter 50 which separately measures
the amounts of electric power for purchase and for sale by
detecting the flow direction of power in the electric power
system. Fig. 2 shows the schematic construction of the
electric power meter 50 of the present embodiment.
As shown in Fig. 2, the electric power meter 50 is
provided in each power consumer H which also functions as a
power supplier. The electric power meter 50 is mounted to a
terminal board (TB) that relays power lines Ltl to Lt3
connected to a column type transformer which transforms

electric power supplied from a power supply company or the
like and supplies it to the respective power consumer H.
The electric power meter 50 mounted to the terminal board
(TB) is provided with, as a power display for displaying the
amounts of electric power for purchase and for sale, which
were separately measured, in a discriminative manner, a
power display unit 51 for displaying the amount of electric
power for purchase and a power display unit 52 for
displaying the amount of electric power for sale.
The electric power meter 50 constructed as such is
covered with a protective cover C that protects the electric
power meter 50. The electric power meter 50 of the present
embodiment is configured as an integral type electric power
meter in which respective elements serving their functions
of measuring or displaying the amount of electric power, or
the power information communication function are integrally
arranged.
The terminal board (TB) to which the electric power
meter 50 is mounted is provided with connection terminals Tl
to T3, which are connected input terminals of the electric
power meter 50 by an internal wiring, and connection
terminals T4 to T6, which are also connected to output
terminals of the electric power meter 50 by the internal
wiring of the terminal board (TB). The connection terminals
Tl to T3 is connected with single-phase 3-wire power lines
Ltl to Lt3 which extend from the column type transformer.

The single-phase 3-wire power lines Ltl to Lt3 consist of
power lines Ltl and Lt3 which transmit electric powers
having opposite phases of 100 V with respect to the ground,
and a neutral power line Lt2 that is earthed to the ground.
The connection terminals T4 to T6 of the terminal board (TB)
respectively connect with power lines Lhl to Lh3 connected
to the distribution switchboard provided in the power
consumer H.
Thus, when electric power is supplied to the
distribution switchboard of the power consumer H via the
column type transformer from the power supply company or the
like, a power supply path is defined in the electric power
meter 50 such that electric power from the transformer is
supplied to the distribution switchboard of the power
consumer H sequentially via the input terminal and output
terminal of the electric power meter 50. In the meantime,
when excess electric power that is generated by the solar
cell 3 or the like provided in the power consumer H is to be
sold to the power supply company or the like, a power supply
path is defined in the electric power meter 50 such that
excess electric power of the power consumer H inversely
flows toward the column type transformer from the power
consumer H sequentially via the output terminal and input
terminal of the electric power meter 50.
According to the electric power meter 50 constructed
as such, when electric power is supplied from the power

supply company or the like to the power consumer H, the
supplied power flows from the input terminal of the electric
power meter 50. Then, the electric power meter measures the
amount of electric power for purchase based on the direction
of flow of the electric power. In the meantime, when excess
electric power generated by the solar cell 3 or the like is
sold to the power supply company or the like from the power
consumer H, a target excess electric power to be sold
reversely flows from the output terminal of the power
consumer H toward the column type transformer, i.e. from the
output terminal toward the input terminal of the electric
power meter 50.
Then, the electric power meter measures the amount of
electric power for sale based on the direction of flow of
the electric power. Thus, the amounts of electric power for
purchase and for sale for each power consumer H can be
measured together, so that a plurality of pieces of power
information such as the amounts of electric power for
purchase and for sale can be reasonably measured by the
unitary electric power meter. Then, the amounts of electric
power for purchase and for sale of the power consumer H,
which were measured by the electric power meter 50, are
transmitted to the measuring center 100 via power line
carrier communication using the power lines Ltl to Lt3 as a
communication medium.
In addition, as shown in Fig. 3, the amounts of

electric power for purchase and for sale, which were
measured by the electric power meter 50, are separately
displayed by the power display unit 51 which displays the
amount of electric power for purchase and the power display
unit 52 which displays the amount of electric power for
sale. In the present embodiment, the amounts of electric
power for purchase and for sale, which were respectively
measured by the electric power meter 50, are physically
divided and displayed by the power display units 51 and 52
for displaying the amounts of electric power for purchase
and for sale, so that the amounts of electric power can be
separately displayed.
Next, the internal structure of the electric power
meter 50 will be described with reference to Fig. 4. As
shown in Fig. 4, the input terminals Tml to Tm3 constituting
the electric power meter 50 are connected to the power lines
Ltl to Lt3 by internal wiring and the connection terminals
Tl to T3 of the terminal board (TB) . The supply power
(electric power for purchase) input from the input terminals
Tml to Tm3 is supplied to the distribution switchboard of
the power consumer H along wiring paths Lml to Lm3 in the
electric power meter 50, which respectively correspond to
the power lines Ltl to Lt3, sequentially via: the output
terminals Tm4 to Tm6, the internal wiring of the terminal
board (TB), the connection terminals T4 to T6, and the power
lines Lhl to Lh3 of the electric power meter 50.

In the meantime, the target excess power for sale
(electric power for sale) generated by the solar cell 3 or
the like is input from the output terminals Tm4 to Tm6 of
the electric power meter 50 and is supplied toward the
column type transformer from the power consumer H along
wiring paths Lm1 to Lm3, sequentially via the input
terminals Tm1 to Tm3, the internal wiring of the terminal
board (TB), the connection terminals T1 to T3, and the power
lines Lt1 to Lt3 of the electric power meter 50.
Further, the sets of magnitude and direction of
voltage of the electric power for purchase and for sale are
respectively measured by a first voltage meter unit 101,
which is arranged between the wiring path Lml corresponding
to the power line Ltl and the wiring path Lm2 corresponding
to the neutral power line Lt2, and a second voltage meter
unit 102, which is arranged between the wiring path Lm2
corresponding to the neutral power line Lt2 and the wiring
path Lm3 corresponding to the power line Lt3. In addition,
the sets of the magnitude and direction of the current of
the supply power are measured by a first current meter unit
103 arranged at the middle of the wiring path Lml and a
second current meter unit 104 arranged at the middle of the
wiring path Lm3.
The magnitudes and directions of voltage and current
that were measured are used to calculate the amounts of
electric power for purchase and for sale, and are input to a

control circuit 110 that controls a display function or
communication function using the power display units 51 and
52 which are resepcetively for displaying the amounts of
electric power for purchase and for sale. The control
circuit 110 determines whether the target electric power to
be measured is electric power for purchase or electric power
for sale based on the direction of input voltage or current.
Under such determination, by multiplying the magnitudes of
the respective input voltage and current, the amounts of
electric power for purchase and for sale that are inputted
to the electric power meter 50 are calculated. Then, the
electric power is added up for a certain time period such as
a day, a week,, or a month, and the measuring time of the
summed electric power, i.e. the measuring time of the
amounts of electric power for purchase and for sale, is
obtained from a clock circuit 111.
Then, power information about the electric power for
purchase and for sale over a certain time period is
separately stored in a memory circuit 112, together with the
respective measuring time thereof. Then, the power
information about the measured electric power for purchase
is outputted to a first display circuit 113 which controls a
display function of the power display unit 51, so that the
power display unit 51 displays the power information about
the electric power for purchase inputted to the first
display circuit 113 in a manner shown in Fig. 3. In the

meantime, the power information about the measured electric
power for sale is outputted to a second display circuit 114
which controls a display function of the power display unit
52, so that the power display unit 52 displays the power
information about the electric power for sale inputted to
the second display circuit 114 in a manner shown in Fig. 3.
Then, the power information about the electric power
for purchase and for sale calculated by the control circuit
110 is output from the control circuit 110 to a power line
communication circuit 120. In the power line communication
circuit 120, when the power information is transmitted, the
power information input from the control circuit 110 is
modulated to a PLC (power line communication) signal that
overlaps the power lines Lt1 to Lt3 because the band of the
power information is increased to a communication frequency
band for power line carrier communication. The modulated
PLC signal is outputted to a transceiver circuit 121 that
adjusts the level of the signal or the like. In the
meantime, when the PLC signal is received, the PLC signal
inputted from the transceiver circuit 121 by the power line
communication circuit 120 is demodulated.
Then, the PLC signal is inputted to a coupling circuit
122 via the transceiver circuit 121. The coupling circuit
122 functions as a filter that filters a frequency out of
the frequency band of the PLC signal in the AC supply power
supplied from a power source B which supplies AC power to

the electric power meter 50. Generally, an input circuit of
the power source B is connected to a condenser for
preventing noise from being emitted to the outside, and the
condenser decreases the impedance within a band of a
communication frequency which is used in the power line
carrier communication of the power line connected to the
input circuit of the power source.
Thus, in the present embodiment, in order to carry out
high efficiency power line carrier communication using the
power line communication circuit 120, the transceiver
circuit 121, and the coupling circuit 122, an impedance
upper 123 for preventing reduction of impedance within a
band of a communication frequency of the power line is
provided between the power line and the power source B.
Thus, the power source B can be connected to the input
terminals Tm1 and Tm3 while restricting the reduction of
impedance within the band of the communication frequency
between the input terminals Tml and Tm3.
The PLC signal output from the coupling circuit 122 is
transmitted to the measuring center 100 while being carried
along the power lines Lt1 to Lt3.
Further, when transmitting the PLC signal, i.e. the
power information, two types of information such as the
electric power for purchase and electric power for sale are
transmitted to the measuring center 100 from the unitary
electric power meter 50. Because of this, in order for the

measuring center 100, to which the two types of power
information are transmitted, to manage the power information
for purchase and the power information for sale of the power
consumer H differently, it needs to transmit the two types
of power information, measured by the electric power meter
50, in a discriminative manner.
Thus, in the present embodiment, as shown in Fig. 5,
the power information Ib for purchase and the power
information Is for sale are alternately transmitted to the
measuring center 100 in sequence. Thus, the electric power
meter 50 can transmit respective power information Ib for
purchase and power information Is for sale to the measuring
center 100 in a discriminative manner based on a timing when
the respective power information Ib and Is is transmitted,
while sharing a single communication interface.
As previously described, according to the electric
power meter of the present embodiment, the following effects
can be obtained.
(1) The electric power meter is configured such that
it detects the flow of power in the electric power system
between the column type transformer and the distribution
switchboard of the power consumer H and distinguishes
between the amount of electric power for purchase and for
sale on the basis of the detected direction of the flow of
power, and separately measures the amounts of electric power
for purchase and for sale. Thus, the amounts of electric

power for purchase and for sale can be separately measured
together by the electric power meter 50, so that a plurality
of pieces of power information about a respective power
consumer, such as the amounts of electric power for purchase
and for sale, can be reasonably measured by a unitary
electric power meter.
(2) The electric power meter is configured such that
the power display displays the amounts of electric power for
purchase and for sale, which were separately measured, in a
discriminative manner and the power display is composed of
two separate power display units 51 and 52 for displaying
the amounts of electric power for purchase and for sale,
respectively. Because of this, when the amounts of electric
power for purchase and for sale are measured by the unitary
electric power meter 50, the unitary electric power meter
can display two kinds of power information such as the
amounts of electric power for purchase and for sale, in a
discriminative manner.
Further, the power display is composed of the power
display units 51 and 52 for displaying the amounts of
electric power for purchase and for sale, so that the
measured amounts of electric power for purchase and for
sale, which were measured by the electric power meter 50,
can be physically divided and separately displayed, and it
is easy to discriminate between the amounts of electric
power for purchase and for sale.

(3) The electric power meter is configured such that
the power information Ib and Is for electric power for
purchase and for sale, which was measured by the electric
power meter 50, is alternately transmitted to the measuring
center 100 in sequence. Thus, the electric power meter 50
can transmit respective power information Ib for purchase
and power information Is for sale to the measuring center
100 in a discriminative manner based on timing when the
respective power information Ib and Is is transmitted, while
using a single communication interface. Thus, when
configuring the remotely measurable electric power meter 50
that is capable of measuring both the amounts of electric
power for purchase and for sale, the amounts of electric
power for purchase and for sale in each power consumer H,
which are transmitted from the electric power meter 50 to
the measuring center 100, can be managed with high
reliability.
(4) Communications between the electric power meter
50 and the measuring center 100 are implemented by of the
electric power meter using power line carrier communication
having power lines Lt1 to Lt3 as a communications medium.
Thus, when the power information Ib and Is for electric
power for purchase and for sale, measured by the electric
power meter 50, is transmitted to the measuring center 100,
there is no need to provide a separate communication path,
but it is possible to secure a dedicated communications path

using an existing communications medium.
(Second Embodiment)
A second embodiment that embodies the electric power
meter of the present invention will now be described with
reference to Figs. 6 to 8B. The electric power meter of the
second embodiment is configured such that the power display
is composed of a single display screen, and other
constructions thereof are the same as in the former
embodiment.
Fig. 6 is a view corresponding to Fig. 2, which shows
the schematic construction of an electric power meter 60 of
the second embodiment. In Fig. 6, the same reference
numerals are used to depict the same elements as those shown
in Fig. 2, and overlapping descriptions thereof will be
omitted.
That is to say, as shown in Fig. 6, the electric power
meter 60 is configured such that the power display is
composed of a single display screen having a common display
section 61 on which both the amounts of electric power for
purchase and for sale are displayed in common.
When the amounts of electric power of the power
consumer for purchase and for sale were measured by the
electric power meter 60, as shown in Fig. 7, the common
display section 61 alternately displays both the amounts of
electric power for purchase and for sale in a time-division
manner.

When the amount of electric power for sale, which is
generated by the solar cell 3 or the like of the power
consumer H, is displayed, as shown in Fig. 8A, the common
display section 61 displays information including an intent
of sale and the amount of electric power to be sold. In the
meantime, when the amount of electric power for purchase
supplied from the power supply company or the like to the
power consumer H is displayed, as shown in Fig. 8B, the
common display section 61 displays information including an
intent of purchase and the amount of electric power to be
purchased. Thus, the amounts of electric power for purchase
and for sale, which were measured by the electric power
meter 60, can be displayed in a discriminative manner, using
a common display section.
As previously described, according to the electric
power meter of the embodiment, the effect similar to the
effects (1), (3), and (4) can be obtained, and the following
effects can also be obtained instead of the effect (2).
(5) It is configured such that the power display is
composed of a single display screen having a common display
section 61 on which both the amounts of electric power for
purchase and for sale are displayed in common. Thus, when
displaying both the amounts of electric power for purchase
and for sale, which were measured by the electric power
meter 60, in a discriminative manner, the structure of the
power display can be simplified.

(6) It is configured such that the common display
section 61 alternately displays the amounts of electric
power for purchase and for sale in sequence. Thus, the
variance in the amounts of electric power for purchase and
for sale can be monitored.
(Third Embodiment)
A third embodiment that embodies the electric power
meter of the present invention will now be described with
reference to Figs. 9 and 10. The electric power meter of
the third embodiment is configured such that the electric
power meter is a unit-type electric power meter, and the
other constructions thereof are the same as in the former
embodiment.
Fig. 9 is a view corresponding to Fig. 2, which shows
the schematic construction of an electric power meter 70 of
the third embodiment. In Fig. 9, the same reference
numerals are used to depict the same elements as those shown
in Fig. 2, and overlapping descriptions thereof will be
omitted.
That is to say, as shown in Fig. 9, the electric power
meter 70 is composed of three units including a
communication unit 70A, a power metering unit 70B, and a
load breaker unit 70C, which are mounted to the terminal
board (TB). The power metering unit 70B detects the amounts
of electric power for purchase and for sale based on the
direction of the flow of power in the power system, and the

detected amounts of electric power for purchase and for sale
are displayed on power display units 71 and 72 which are for
displaying the amounts of electric power for purchase and
for sale and constitute the power display.
The communication unit 70A receives the amounts of
electric power for purchase and for sale, which were
measured by the power metering unit 70B, and transmits the
received amounts of electric power for purchase and for sale
to the measuring center 100 via power line carrier
communication using the power lines Lt1 to Lt3 as a
communications medium. Further, the power metering unit 70B
receives a variety of types of information or control
commands from the measuring center 100 or the like via. the
communication unit 70A.
Further, the load breaker unit 70C performs a breaking
action depending on control commands from the power supply
company or the like which are received by the power metering
unit 70B. For example, when the power consumer H has moved
in or out, the load breaker unit may perform power-feeding
or power-breaking.
Next, the internal structure of the electric power
meter 70 will be described with reference to Fig. 10. Fig.
10 is a view corresponding to Fig. 4, which shows the
internal structure of the electric power meter 70 of the
third embodiment. In Fig. 10, the same reference numerals
are used to indicate the same elements as those shown in

Fig. 4, and overlapping descriptions thereof will be
omitted.
The power metering unit 70B of the electric power
meter 70 includes a control circuit 110, a first and a
second voltage meter unit 101 and 102, a first and a second
current meter unit 103 and 104, a clock circuit 111, a
memory circuit 112, and first and second display circuits
113 and 114, which are the same as those of Fig. 4, so
descriptions thereof will be omitted.
That is to say, the electric power meter 70 is
configured to further include an interface 130 for a
communications unit which constitutes the communications
unit 70A, and a breaker controller 140 which constitutes the
load breaker unit 7 0C. The power information about the
electric power for purchase and for sale input from the
control circuit 110 via the interface 130 of the
communications unit is transmitted to the measuring center
100 through a power line (not shown).
In addition, the interface 130 of the communication
unit receives a variety of types of information or control
commands from the measuring center 100 or the like, and
outputs them to the control circuit 110. Meanwhile, the
breaker controller 140 controls the load breaker unit 70C to
perform a load breaking action depending on the control
commands which are received by the interface 130 of the
communication unit and input to the control circuit 110.

In the electric power meter 70, when the amounts of
electric power of the power consumer H for purchase and for
sale have been measured, the measured amounts of electric
power for purchase and for sale are respectively displayed
on the power display unit 71 and 72 which are for displaying
the amounts of electric power for purchase and for sale. In
addition, the amounts of electric power for purchase and for
sale are alternately transmitted from the communication unit
70A to the measuring center 100 in sequence. Thus, the
electric power meter 70 can concurrently measure the amounts
of electric power of the power consumer H for purchase and
for sale, and display and transmit the measured amounts of
electric power for purchase and for sale in a discriminative
manner.
As previously described, according to the electric
power meter of the present embodiment, the effects similar
to the effects (1) to (4) can be obtained, and the following
effect can also be obtained.
(5) The electric power meter is configured such that
the electric power meter is a unit-type electric power meter
7 0 that is capable of separately measuring the amounts of
electric power for purchase and for sale based on the
direction of the flow of power in the power system. Thus,
although the communication means or display means of the
electric power meter 70 may be changed and made different,
such a situation can be flexibly dealt with by replacing the

communication unit 70A, the power metering unit 70B, and the
load breaker unit 70C, which constitute the electric power
meter 70, thereby improving the degree of freedom of the
electric power meter 70.
(Other Embodiment)
The former embodiments may also be implemented as
follows.
While the former embodiments are configured such that
the power information Ib and Is for electric power for
purchase and for sale, which was measured by the electric
power meters 50 to 70, is alternately transmitted to the
measuring center 100 in sequence, the present invention is
not limited thereto, but may be configured such that it is
determined whether the amount of electric power is for
purchase or for sale, based on the direction of the flow of
power in the power system, and the amount of power that is
measured at that time is selectively transmitted to the
measuring center 100 according to the determination.
According to this construction, the electric power meter can
transmit the power information Ib and Is about the electric
power for purchase and for sale as a group of separate power
information to the measuring center 100 while using a single
communication interface in common.
Thus, when configuring the remotely measurable
electric power meter that is capable of measuring both the
amounts of electric power for purchase and for sale, the

amounts of electric power for purchase and for sale of each
power consumer can be managed with high reliability. When
it is configured such that the amount of power that is to be
measured is selectively transmitted to the measuring center
100 based on the determination of the amount of electric
power for purchase or for sale, only the power information
to be measured is transmitted to the measuring center 100,
so that it is possible for the electric power meter to
transmit at least the power information required for remote
measuring to be performed.
While the former embodiments are configured such that
the communications between the electric power meters 50 to
7 0 and the measuring center 100 is implemented via power
line carrier communication having power lines Ltl to Lt3 as
a communications medium, the present invention is not
limited thereto, and may be configured such that any
communications medium between the electric power meters 50
to 70 and the measuring center 100 may be used so long as it
can transmit the power information measured by the electric
power meters 50 to 70 to the measuring center 100, and the
communications between the electric power meters 50 to 70
and the measuring center 100 may be implemented using
wireless communication or the like.
While the former embodiments are configured such that
the electric power meters 50 to 70 have a communication
function whereby the power information Ib and Is about

electric power for purchase and for sale, which was
separately measured, is automatically transmitted to the
measuring center 100 that is the management center of the
electric power meters, the present invention is not limited
thereto, but may be configured such that when measuring the
amounts of electric power of the power consumer H for
purchase and for sale with a unitary electric power meter,
the communications function of the electric power meters 50
to 70 is omitted.
While the second embodiment is configured such that
the amounts of electric power for purchase and for sale are
alternately displayed on the common display section 61 in a
time-division manner, the present invention is not limited
thereto, and may be configured such that it is determined
whether the amount of electric power is for purchase or for
sale, based on the direction of the flow of power in the
power system, and the amount of power to be measured at that
time according to the determination is selectively displayed
on the common display section 61.
While the third embodiment is configured such that the
power display constituting the electric power meter 70 is
composed of two display units including the power display
units 71 and 72 for displaying the amounts of electric power
for purchase and for sale, the present invention is not
limited thereto, and may be configured so that as shown in
Figs. 6, 8A, and 8B, the power display is composed of a

power display having a common display section on which both
the amounts of electric power for purchase and for sale are
displayed in common.
The first and third embodiments were configured such
that the power display is composed of two display units
including the power display units 51 and 71 for displaying
the amount of electric power for purchase and the power
display units 52 and 72 for displaying the amount of
electric power for sale, and the second embodiment was such
that the power display is composed of the power display
having the common display section 61 on which both the
amounts of electric power for purchase and for sale are
displayed in common in a time-division manner.
However, the present invention is not limited thereto.
Any power display may be used so long as it can display the
amounts of electric power for purchase and for sale, which
were measured by the electric power meter, in a
discriminative manner. Further, when measuring the amounts
of electric power for purchase and for sale using the
unitary electric power meter, the electric power meter may
include a power display which displays only one of the
amount of electric power for purchase or the amount of
electric power for sale.
While the invention has been shown and described with
respect to the embodiments, the present invention is not
limited thereto. It will be understood by those skilled in

the art that various changes and modifications may be made
without departing from the scope of the invention as defined
in the following claims.

We claim:
1. An electric power meter separately measuring an amount
of electric power for purchase supplied from an electric
power system and an amount of electric power for sale which
is generated by an electricity generation device,
wherein the electric power meter detects a power flow
of the electric power system and separately measures the
amount of electric power for purchase and the amount of
electric power for sale while distinguishing between the
amount of electric power for purchase and the amount of
electric power for sale on the basis of a direction of the
detected power flow.
2. The electric power meter according to claim 1, wherein
the electric power meter is provided with a power display
that displays the amount of electric power for purchase and
the amount of electric power for sale, which were separately
measured, in a discriminative manner.
3. The electric power meter according to claim 2, wherein
the power display includes two separate display units that
consist of a display unit which displays the amount of
electric power for purchase and a display unit which
displays the amount of electric power for sale.

4. The electric power meter according to claim 2, wherein
the power display is composed of a single display screen
having a common display section on which both the amount of
electric power for purchase and the amount of electric power
for sale are displayed in common.
5. The electric power meter according to claim 4, wherein
the common display section of the power display displays the
amount of electric power for purchase and the amount of
electric power for sale in a time-division manner.
6. The electric power meter according to any one of claims
1 to 5, wherein the electric power meter has a communication
function of automatically transmitting the amount of
electric power for purchase and the amount of electric power
for sale, which were separately measured, to a measuring
center that is a management center of the electric power
meter, in such a manner as to alternately transmit
information about both the amounts of electric power for
purchase and for sale to the measuring center in sequence.
7. The electric power meter according to any one of claims
1 to 5, wherein the electric power meter has a communication
function of automatically transmitting the amount of
electric power for purchase and the amount of electric power
for sale, which were separately measured, to a measuring

center that is a management center of the electric power
meter, in such a manner as to selectively transmit to the
measuring center a measured amount of electric power
whenever determination is made whether the amount of
electric power is for purchase or for sale.
8. The electric power meter according to claim 6 or 7,
wherein the communication function is implemented by power
line communication wherein a power line is a communication
medium.
9. The electric power meter according to any one of
claims 1 to 8, wherein the electric power meter is a
unit-type electric power meter.

ABSTRACT

An electric power meter separately measures an amount
of electric power for purchase supplied from an electric
power system and an amount of electric power for sale which
is generated by an electricity generation device. The
electric power meter detects a power flow of the electric
power system and separately measures the amount of electric
power for purchase and the amount of electric power for sale
while distinguishing between the amount of electric power
for purchase and the amount of electric power for sale on
the basis of a direction of the detected power flow.