JP2013190208A - Power measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power measuring apparatus with a reduced surge voltage and/or surge current applied to circuit components constituting a communication section.SOLUTION: A main body unit 1A of a power measuring apparatus includes: a power calculation section 13 that calculates power consumption in a measurement circuit on the basis of measurement results by a current measurement unit 11 and a voltage measurement unit 12; a communication section 15 that outputs a measurement result of the power consumption to a management apparatus 100 connected thereto via a communication line CB5; a power supply circuit 17 that supplies operation power to an inner circuit; a connection terminal T13 to which a ground line CB3 is connected for grounding to protect the power supply circuit 17; and a connection terminal T16 to which a shield line CB6 is connected for electromagnetically shielding the communication line CB5. The connection terminal T13 and the connection terminal T16 are gap-coupled with each other via a gap arrestor 18. Therefore, when static electricity is applied to the communication section 15 in an ungrounded state, the gap arrestor 18 conducts the electricity so that the static electricity can be released to the ground.

Description

  The present invention relates to a power meter.

  In office buildings, retail stores, universities, etc., electricity received from the distribution system of the power company is split into multiple branch circuits using the switchboard and distribution board, and power is supplied to the loads connected to each branch circuit. doing.

  Previously, the main current was measured at the point of power distribution, and the total power consumption was measured based on this main current. However, in recent years, awareness of power saving and power saving has increased, and individual branch circuits have There is a demand to measure power consumption and to consider measures for power saving and power saving. For example, the multi-circuit wattmeter disclosed in Patent Document 1 can measure power consumption at a plurality of points, and can increase the number of measurement points by adding an extension unit.

JP-A-2005-55404

  Since the multi-circuit wattmeter disclosed in Patent Document 1 is installed on a switchboard or distribution board, it is necessary to go to the place where the switchboard or distribution board is installed in order to check the measurement result of power consumption. It took time and effort.

  Therefore, the power consumption measurement results are periodically transmitted from the multi-circuit power meter to an external device (for example, a management server) installed in a place where it can be easily seen by power consumers and facility managers. It can be displayed on the device. In this case, the connection terminal for connecting the communication line connecting the communication unit included in the multi-circuit power meter and the external device is provided in a state of being exposed on the surface of the multi-circuit power meter. Therefore, when some work (for example, work to connect a communication line to the connection terminal) is performed in the panel, the operator's body may touch the connection terminal. If static electricity charged on the operator's body is discharged to the connection terminal when the communication unit is not grounded, surge voltage or surge current due to static electricity may be applied to the circuit components that make up the communication unit. was there. For this reason, it is necessary to use a high breakdown voltage component for the circuit component that constitutes the communication unit, resulting in an increase in cost.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a power measuring instrument in which a surge voltage and a surge current applied to circuit components constituting a communication unit are reduced.

  In order to solve the above-described problem, a power measuring instrument of the present invention includes a power measuring unit, a communication unit, a power supply circuit unit, a first ground terminal, and a second ground terminal. The power measuring unit measures power consumption by the load. A communication part outputs the measurement result of the said electric power measurement part to the external apparatus connected via the communication line. The power supply circuit unit receives power supply from an external power supply and supplies operating power to the power measurement unit and the communication unit. A ground line for protecting and grounding at least one of the power supply circuit unit and the power measurement unit is connected to the first ground terminal. The second ground terminal is provided to connect a shield wire that electromagnetically shields the communication line. The first ground terminal and the second ground terminal are gap-coupled via a discharge gap.

  In this power meter, the discharge gap is preferably a gap arrester.

  In this power meter, a first circuit board on which a high-power circuit including the power measurement unit and the power supply circuit unit is mounted, and a second circuit board on which a weak-power circuit including the communication unit is mounted. Prepare. The discharge gap is preferably a pattern gap formed on one of the first circuit board and the second circuit board.

  In this power meter, a first circuit board on which a high-power circuit including the power measurement unit and the power supply circuit unit is mounted, and a second circuit board on which a weak-power circuit including the communication unit is mounted. Prepare. The container for storing the first circuit board and the second circuit board is configured by combining a body and a cover, and the first circuit board is stored in one of the body and the cover, and the body and the cover The second circuit board is housed in the other of the covers. The first circuit board and the second circuit board are respectively provided with conductive protrusions facing each other with a predetermined gap in a state where the body and the cover are assembled, It is also preferable that the discharge gap is configured as follows.

  According to the present invention, when static electricity is applied to the terminal to which the communication line is connected while the shield wire is not connected to the second ground terminal, the discharge gap is conducted and the static electricity is released from the first ground terminal to the ground. As a result, the circuit components constituting the communication unit can be protected from static electricity.

The main body unit used for the electric power meter of this embodiment is shown, (a) is a block diagram in the state where the communication line is not connected, (b) is a block diagram in the state where the communication line is connected. It is a schematic sectional drawing same as the above. (A) is a front view of the same, (b) is a top view, and (c) is a bottom view. (A) is a left side view of the above, and (b) is a right side view. It is an external appearance perspective view same as the above. It is an external appearance perspective view of the state which isolate | separated the main body unit and extension unit used for the same as the above. It is a schematic sectional drawing which shows the other form same as the above.

  Embodiments of a power meter according to the present invention will be described below with reference to FIGS.

  The power measuring instrument of this embodiment is installed in a panel such as a distribution board or distribution board together with a main switch or branch switch, and is used to measure power consumption or power consumption in the main circuit or branch circuit. Is done.

  As shown in FIGS. 3 to 6, the power measuring instrument of the present embodiment includes a main unit 1 </ b> A and one or more extension units 1 </ b> B connected to the main unit 1 </ b> A as necessary.

  1A and 1B are block diagrams of the main unit 1A. The power meter displays the power consumption measurement result on the display unit or stores it in a memory card, and uses it to send the measurement result to an external device connected via a communication line. There is a method. FIG. 1A shows a wiring configuration when the power meter is used alone, and FIG. 1B shows a wiring configuration when the power meter is connected to the management apparatus 100 which is an external device. Yes. Generally, it is considered that the power meter is often used alone at the initial stage of introduction of the power meter into the power distribution system. When the power meter is used alone, the user needs to regularly go to the place where the power meter is installed and collect the memory card in order to collect the measurement data stored in the memory card. . During the subsequent operation, the user is expected to increase the number of measurement objects. When the measurement object exceeds a certain scale, a communication line is used between the power meter and the management apparatus 100 to facilitate collection of measurement data. It is thought that measurement data will be transmitted by communication after connection.

  The main unit 1A constituting the power measuring instrument of the present embodiment includes a current measuring unit 11, a voltage measuring unit 12, a power calculating unit 13, a memory card interface unit 14, a communication unit 15, and a display unit 16. The power supply circuit unit 17 and the gap arrester 18 are provided.

  An output line CB4 of the current transformer 11a is connected to the current measuring unit 11. An electric wire through which a current to be measured flows is inserted into the core hole of the current transformer 11a. The current measuring unit 11 measures the current value to be measured based on the output signal of the current transformer 11a. In the three-phase four-wire distribution method, current is measured in each of the R phase, S phase, and T phase, so that three current transformers 11a are required, and the connection portions to which the current transformers 11a are connected respectively. Are required for each circuit. Further, in the present embodiment, three connection portions are set as one set so that the current for three circuits can be measured by one main unit 1A, and three sets (that is, nine) of connection portions are the main unit 1A. Is provided.

  The voltage measuring unit 12 detects a voltage applied to a circuit to be measured, that is, a power supply voltage of a commercial AC power supply AC that is an external power supply. In the three-phase four-wire distribution method, the voltage of each phase is measured by the voltage measuring unit 12.

  The power calculation unit 13 periodically fetches the measurement results from the current measurement unit 11 and the voltage measurement unit 12, and uses the measured values of the current and voltage and the phase difference between the current and voltage, Data such as power consumption is calculated. The power calculation unit 13 outputs measurement results such as power consumption and power consumption to the memory card I / F unit 14, the communication unit 15, and the display unit 16. The current measuring unit 11, the voltage measuring unit 12, and the power calculating unit 13 constitute a power measuring unit.

  The memory card interface unit (hereinafter referred to as a memory card I / F unit) 14 includes a card slot to which a memory card MC1 such as an SD card is detachably connected. When the measurement result is input from the power calculation unit 13, the memory card I / F unit 14 writes data to the memory card MC1, and the measurement data such as power consumption and power consumption for each circuit is sometimes stored. Records in series on the memory card MC1. The power calculation unit 13 may store measurement data such as power consumption and power consumption measured for each circuit in a main body memory (not shown).

  The communication unit 15 is compliant with the RS485 standard, which is a serial communication standard, and is connected via a transmission line CB5 (Tx line, Rx line) on the transmission side and the reception side each formed of a twisted pair line as shown in FIG. It is connected to the management apparatus 100 and performs serial communication with the management apparatus 100. When the management device 100 is connected to the main unit 1 </ b> A, the communication unit 15 transmits the measurement result to the management device 100 when the measurement result is input from the power calculation unit 13. Further, the main unit 1 </ b> A causes the past measurement results stored in the memory card MC <b> 1 to be transmitted from the communication unit 15 to the management apparatus 100 in response to a transmission request from the management apparatus 100. The main unit 1 </ b> A may cause the past measurement results stored in the main body memory to be transmitted from the communication unit 15 to the management apparatus 100 in response to a transmission request from the management apparatus 100.

  The display unit 16 is configured by a liquid crystal display, for example, and displays the measurement result when the measurement result is input from the power calculation unit 13. The display unit 16 displays various setting contents and operation states in addition to the measurement results. The display unit 16 may be integrated with the main unit 1A, may be a separate unit, or may be a display lamp such as a light emitting diode.

  The power supply circuit unit 17 is supplied with power from the commercial AC power supply AC, which is an external power supply, via the power cable CB1, and receives a current measurement unit 11, a voltage measurement unit 12, a power calculation unit 13, and a memory card I / F unit 14. Then, operation power for the communication unit 15 and the display unit 16 is generated and supplied to each unit. The power supply circuit unit 17 supplies operating power to the extension unit 1B connected to the main unit 1A.

  Here, in the circuit shown in FIG. 1, a high-power circuit including a power measurement unit (consisting of a current measurement unit 11, a voltage measurement unit 12, and a power calculation unit 13) and a power supply circuit unit 17 is a first circuit board B1. The low-power circuit including the communication unit 15 is mounted on the second circuit board B2. In FIG. 1, the current measurement unit 11, the voltage measurement unit 12, and the power calculation unit 13 are illustrated as being mounted on the first circuit board B <b> 1, but the current measurement unit 11 and the power calculation unit 13 include Since the high current does not flow, it may be mounted on the second circuit board B2. Further, each of the first circuit board B1 and the second circuit board B2 may be composed of one circuit board, or may be composed of a plurality of circuit boards. In this way, the strong electric circuit and the weak electric circuit are mounted on separate circuit boards, and the strong electric first circuit board B1 and the weak electric second circuit board B2 are arranged apart from each other. The noise applied to the weak electric circuit is reduced by the influence of the current and voltage flowing through the circuit.

  As shown in FIGS. 1 and 3, the main unit 1 </ b> A includes connection terminals T <b> 11 to T <b> 13 and T <b> 15 to T <b> 17 each formed of a screw terminal device and a receptacle-type connector for electrical connection with an external circuit. Connector CN11. In the block diagrams of FIGS. 1A and 1B, the connection terminal T17 and the connector CN11 are not shown.

  A two-core power cable CB1 from a commercial AC power supply AC is connected to the connection terminal T11. A commercial AC power supply AC is supplied to the power supply circuit unit 17 via a connection terminal T11.

  The connection terminal T12 is connected to a cable for inputting the voltage at the measurement point to the voltage measuring unit 12. In the case of three-phase four-wire distribution, the voltages of the R phase, S phase, and T phase are set. Are input through the cable CB2.

  A ground line CB3 for connecting the power supply circuit unit 17 to the ground (ground) is connected to the connection terminal T13 which is the first ground terminal.

  A communication line CB5 that connects between the communication unit of the management apparatus 100 and the communication unit 15 is connected to the connection terminal T15. The communication line CB5 is composed of one pair or two pairs of twisted pair lines (Tx line, Rx line), and the connection terminal T15 is composed of two or four screw terminal devices.

  The connection terminal T16, which is the second ground terminal, is composed of two screw terminal devices, and each screw terminal device is connected to a shield wire CB6 that electromagnetically shields one or two pairs of twisted pair wires constituting the communication line CB5. Is done.

  The connection terminal T17 and the connector CN11 are provided for connecting the output line CB4 of the current transformer 11a, and the output signal of the current transformer 11a is input to the current measuring unit 11 via the connection terminal T17 or the connector CN11. In the present embodiment, the current measuring unit 11 can be connected to any of two types of current transformers 11a (for example, 400A and 5A) having different measurement ranges. The circuit on the input side differs depending on the type of the current transformer 11a, and the output line CB4 is connected to the connection terminal T17 made of a screw terminal device in the current transformer 11a having a measurement range of 400A. In the current transformer 11a having a measurement range of 5A, the plug-type connector connected to the terminal of the output line CB4 is connected to the connector CN11 formed of a receptacle-type connector.

  The gap arrester 18 is made of a gas-filled discharge tube, for example, and is mounted on the first circuit board B1 together with a high-voltage circuit as shown in FIG. One terminal of the gap arrester 18 is electrically connected to the connection terminal T13 (first ground terminal) via the wiring pattern 20 of the first circuit board B1. The other terminal of the gap arrester 18 is electrically connected to a plated through hole (not shown) provided in the first circuit board B1 via the wiring pattern 21 of the first circuit board B1. The second circuit board B2 is provided with a plated through hole (not shown) electrically connected to the connection terminal T16 (second ground terminal) via the wiring pattern 22 of the second circuit board B2. . Both ends of the cable CB7 are soldered to the plated through holes of the first circuit board B1 and the second circuit board B2, respectively, and the gap between the first ground terminal T13 and the second ground terminal T16 via the gap arrester 18. A gap will be joined.

  When this power measuring unit is used alone, the communication line CB5 is not connected to the connection terminal T15, and the shield line CB6 for electromagnetically shielding the communication line CB5 is also not connected to the second ground terminal T16. The communication unit 15 is not grounded. The connection terminal T15 and the second ground terminal T16 are respectively provided in a state exposed on the surface of the main unit 1A so that the communication line CB5 and the shield line CB6 can be connected. Therefore, there is a possibility that the operator's body may come into contact with the connection terminal T15 or the second grounding terminal T16 when any work is performed in the panel on which the main unit 1A is installed. There is a possibility of flowing into the communication unit 15 from the connection terminal T15 or T16. Even in such a case, in the present embodiment, since the first ground terminal T13 and the second ground terminal T16 are gap-coupled via the gap arrester 18, the static electricity is generated by the gap arrester 18 being conducted. One ground terminal T13 can escape to the ground. Therefore, since the surge voltage and surge current applied to the circuit components constituting the communication unit 15 are reduced, it is not necessary to use a high-voltage component for the circuit components constituting the communication unit 15, thereby reducing the cost. Can do.

  In addition, the main unit 1A of the present embodiment can measure the power for three circuits when measuring the power consumption of the load by, for example, a three-phase four-wire power distribution method, but the power can be measured by four or more circuits. When measurement is desired, the extension unit 1B is connected to the main unit 1A. As with the main unit 1A, the extension unit 1B can measure power for three circuits, and only the required number of extension units 1B are connected to the main unit 1A. The extension unit 1B has a current measuring unit (not shown) for a plurality of circuits (for example, three circuits), and outputs a current measurement result measured by the current measuring unit to the main unit 1A. In the main unit 1A, the power calculation unit 13 periodically fetches the current measurement value of the circuit to be measured from the extension unit 1B, and the measurement target is based on the current measurement value and the voltage value measured by the voltage measurement unit 12. Data such as power consumption and power consumption of the circuit is obtained by calculation. Then, when the power calculation unit 13 calculates data such as power consumption and power consumption of the circuit that is the measurement target of the extension unit 1B, the measurement result is sent to the memory card I / F unit 14, the communication unit 15, and the display unit. 16 and so on.

  The circuit configurations of the main unit 1A and the extension unit 1B are as described above, and the structures of the main unit 1A and the extension unit 1B will be described below with reference to FIGS. In the following description, unless otherwise specified, the vertical and horizontal directions are defined in the state of being installed in the panel (that is, the direction shown in FIG. 3A), and the right side in FIG. I do.

  The container 50 of the main unit 1A is configured by combining a body 51 and a cover 52 each made of a synthetic resin molded product. The body 51 is formed in a rectangular box shape whose front side is open. The cover 52 is formed in a substantially box shape with an open rear side, and is attached to the front side of the body 51 so as to close the opening of the body 51. The protrusions 51e provided on the upper side surface and the lower side surface of the body 51 are fitted into the through holes 52c of the cover 52, so that the body 51 and the cover 52 are coupled (see FIGS. 3 and 6). ).

  On the front surface of the cover 52, step portions 54 and 55 are provided on both sides in the vertical direction, and a table-like protruding portion 53 is provided between the step portion 54 and the step portion 55 so as to protrude forward.

  As shown in FIG. 4A, a rectangular groove 51 a extending in the left-right direction is provided on the back surface of the body 51 in the vicinity of the center in the up-down direction. A rail member (for example, a rail member standardized by the DIN standard or the like) for mounting an internal unit (for example, a main switch or a branch switch) is inserted into the rectangular groove 51a. A claw 51b that engages with the upper piece of the rail member is provided on the upper end surface of the rectangular groove 51a. On the other hand, a claw 56a provided at the upper end of the latch piece 56 projects from the lower end surface of the rectangular groove 51a. The latch piece 56 is provided so as to be movable in the vertical direction with respect to the body 51, and always receives an upward elastic force by a spring portion (not shown). Therefore, in a state where the rail member is inserted into the rectangular groove 51a, the claw 51b is locked to the upper piece of the rail member, and the claw 56a of the latch piece 56 is locked to the lower piece of the rail member. The container 50 is attached to the rail member. The lower part of the latch piece 56 projects downward from the lower end surface of the container body 50, and when the operator pulls the lower part of the latch piece 56 downward, the claw 56a is located inside the lower end face of the rectangular groove 51a. Be drawn into. Thereby, since the latching state of the nail | claw 56a and a rail member is cancelled | released, the container 50 can be removed from a rail member.

  As shown in FIG. 2, the first circuit board B <b> 1 and the second circuit board B <b> 2 are housed inside the container body 50. The high-power first circuit board B <b> 1 is housed in the body 51, and the low-power second circuit board B <b> 2 is housed in the cover 52.

  Of the connection terminals T11 to T13, T15 to T17 and the connector CN11 described above, the connection terminals T11 to T13 are the high-power first circuit board B1, and the connection terminals T15 to T17 and the connector CN11 are the low-power second circuit board B2. Are implemented respectively. An electric wire is inserted into the connection terminals T11 and T13 through a rectangular hole 51c that opens on the lower surface of the body 51, and an electric wire is inserted into the connection terminal T12 through a rectangular hole 51d that opens on the lower surface of the body 51. The terminal screws of the connection terminals T11 to T13 are exposed to the front side from the through holes 55a and 55b provided in the lower step portion 55 of the cover 52, and the terminal screws are screwed with a screwdriver inserted from the through holes 55a and 55b. By tightening, the electric wires are fastened to the connection terminals T11 to T13. In addition, the communication lines CB5 and the shield line CB6 are inserted into the connection terminals T15 and T16 through the wire insertion through hole 52a provided on the upper side surface of the cover 52. The terminal screws of the connection terminals T15 and T16 are exposed to the front side from the through holes 54a provided on the front surface of the stepped portion 54, and are tightened with a screwdriver inserted from the through holes 54a. An electric wire is fastened to the connection terminals T15 and T16. Further, the output line of the current transformer 11a is inserted into each connection terminal T17 through a through hole 52b for inserting a wire provided on the upper side surface or the lower side surface of the cover 52. The terminal screw of each connection terminal T17 is exposed to the front side from the through hole 54b of the step portion 54 or the through hole 55c of the step portion 55, and is tightened with a screwdriver inserted from the through hole 54b or 55c. As a result, the output line is fastened to the connection terminal T17. In the present embodiment, twelve connection terminals T17 are arranged in the upper step portion 54, and six connection terminals T17 are arranged in a row in groups of six in the lower step portion 55. Three connectors CN11 are arranged side by side with the six connection terminals T17 arranged together. Then, six wire connection portions of the connection terminal T17 are exposed from each through hole 52b, and six terminal screws of the connection terminal T17 are exposed from the through holes 54b and 55c, and six connection terminals T17. The three connectors CN11 are exposed side by side.

  The second circuit board B2 is mounted with a dip switch 19 for address setting and light emitting diodes LD1 to LD4 for performing various displays. The dip switch 19 is exposed to the front surface side through a through hole 53b provided in the front surface of the protruding portion 53. The light emitted from the light emitting diodes LD1 to LD4 is emitted forward from a through hole 53c provided in the front surface of the protruding portion 53. Further, a through hole 53d for exposing the card slot SL1 of the memory card I / F portion 14 is also provided on the front surface of the protruding portion 53.

  Next, the structure of the extension unit 1B will be described. The container 60 of the extension unit 1B is configured by connecting a body 61 and a cover 62 each made of a synthetic resin molded product. The body 61 is formed in a rectangular box shape whose front side is open. The cover 62 is formed in a substantially box shape with an open rear side, and is attached to the front side of the body 61 so as to close the opening of the body 61. The projections 61c provided on the upper side surface and the lower side surface of the body 61 are fitted into the through holes 62b of the cover 62, respectively, so that the body 61 and the cover 62 are coupled to each other (see FIGS. 3 and 6). ).

  On the front surface of the cover 62, step portions 64 and 65 are provided on both sides in the vertical direction, and a table-like protruding portion 63 is provided between the step portion 64 and the step portion 65 so as to protrude forward.

  As shown in FIG. 4B, a rectangular groove 61a extending in the left-right direction is provided on the back surface of the body 61 in the vicinity of the center in the up-down direction. On the upper end surface of the rectangular groove 61a, a claw 61b is provided to be engaged with the upper piece of the rail member (not shown) described above. A claw 66a provided at the upper end of the latch piece 66 protrudes from the lower end surface of the rectangular groove 61a. The latch piece 66 is provided so as to be movable in the vertical direction with respect to the body 61 and always receives an upward elastic force by a spring portion (not shown). Therefore, in a state where the rail member is inserted into the rectangular groove 61a, the claw 61b is locked to the upper piece of the rail member, and the claw 66a of the latch piece 66 is locked to the lower piece of the rail member. The container 60 is attached to the rail member. The lower portion of the latch piece 66 protrudes downward from the lower end surface of the container body 60. When the operator pulls the lower portion of the latch piece 66 downward, the claw 66a is located inside the lower end surface of the rectangular groove 61a. Be drawn into. Thereby, since the latching state of the nail | claw 66a and a rail member is cancelled | released, the container 60 can be removed from a rail member.

  Also, two slits 61d opened at the left end are formed on the upper and lower side walls of the body 61, and a flexible piece 61e is provided between the two slits 61d. The right end of the flexible piece 61e is cantilevered on the side wall of the body 61, and the left end of the flexible piece 61e can be bent in the vertical direction. A claw 61f that projects outward is provided at the left end of the flexible piece 61e. Further, on the right side surface of the vessel body 60, grooves 61g are provided on both sides in the vertical direction. On the right side surface of the main body 50 of the main unit 1A, grooves (not shown) similar to those of the extension unit 1B are provided on both sides in the vertical direction. Thus, the main unit 1A and the extension unit 1B are connected to each other by locking the claw 61f of the extension unit 1B in the groove of the main unit 1A while being attached to the rail member. Further, the extension units 1B are also connected to each other by engaging the claws 61f provided on one extension unit 1B with the groove 61g of the other extension unit 1B in a state where each of the extension units 1B is attached to the rail member. .

  A substrate (not shown) on which circuit components such as a current measuring unit are mounted is accommodated in the body 60. As with the main unit 1A, the current measurement unit of the extension unit 1B includes two connection units (connection terminal T21 and connector CN21) to which two types of current transformers 11a having different measurement ranges can be connected. And the current transformer selected according to the magnitude | size of load current is connected to the connection part corresponding to the electric current measurement part of the extension unit 1B, and the electric current value of measurement object is measured. In the present embodiment, three sets of connection terminals T21 and connector CN21 are set as one set so that three circuits (in the case of three-phase four-wire power distribution) can be measured with one extension unit 1B. A connection terminal T21 and a connector CN21 are provided in the extension unit 1B.

  The connection terminal T21 is constituted by a screw terminal device. Twelve connection terminals T21 are provided in the upper step portion 54 of the container body 60, and six connection terminals T21 are provided in the lower step portion 65. It is arranged in a row as a group. Three connectors CN21 are arranged side by side with the six connection terminals T21 arranged together. And the electric wire connection part of the connection terminal T21 is exposed from the through hole 62a for electric wire insertion provided in the upper surface or the lower surface of the cover 62, and the output cable of the current transformer 11a passes through the through hole 62a. Is inserted into the wire connection portion of the connection terminal T21. Further, six terminal screws of the connection terminal T21 are exposed from the through hole 64a of the stepped portion 64 or the through hole 65a of the stepped portion 65, and the terminal screws are screwed with a screwdriver inserted from the through hole 64a or the through hole 65a. By tightening, the output cable is fastened to the connection terminal T21. From the through holes 64a and 65a, three connectors CN21 are exposed alongside the six connection terminals T21, and a plug-type connector (not shown) provided on the output cable of the current transformer 11a is a connector. Connected to CN21.

  The power measuring instrument of the present embodiment has the above-described configuration, and a power cable CB1 from an external power source is connected to the connection terminal T11. The cable CB2 is connected to the connection terminal T12, and the voltage of the circuit to be measured is input to the voltage measurement unit 12. The main unit 1A is provided with a plurality of sets of connection terminals T17 and connectors CN11 for current measurement, and a current transformer 11a corresponding to the circuit current to be measured is selected, and the corresponding connection terminal T17 or connector CN11 is selected. Connected to. The power calculation unit 13 captures the measurement results of the current measurement unit 11 and the voltage measurement unit 12 at a predetermined timing, obtains power consumption and power consumption for each circuit, and displays them on the display unit 16. The power calculation unit 13 outputs the measurement result to the memory card I / F unit 14 and stores the measurement result in the memory card MC1. When the extension unit 1B is connected to the main unit 1A, the power calculation unit 13 takes in the measurement current of each circuit from the extension unit 1B and uses the measurement current and the measurement result of the voltage measurement unit 12 to consume. Find the amount of power. And the electric power calculating part 13 displays the measurement result of the measuring object by the extension unit 1B on the display part 16, or memorize | stores it in memory card MC1. When the management device 100 is connected to the main unit 1A, the main unit 1A transmits the history data of the measurement results stored in the memory card MC1 periodically or in response to a request from the management device 100. To the management apparatus 100. Based on the measurement result transmitted from the main unit 1A, the management device 100 can grasp the power consumption change trend due to the load.

  As described above, the power measuring instrument of the present embodiment includes a power measuring unit (consisting of the current measuring unit 11, the voltage measuring unit 12, and the power calculating unit 13), the communication unit 15, the power supply circuit unit 17, A connection terminal T13 as a first ground terminal and a connection terminal T16 as a second ground terminal are provided. The power measuring unit measures power consumption by the load. The communication unit 15 outputs the measurement result of the power measurement unit to an external device (for example, the management device 100) connected via the communication line CB5. The power supply circuit unit 17 receives power supply from an external power supply (for example, commercial AC power supply AC) and supplies operating power to the power measurement unit and the communication unit 15. A ground line CB3 for protective grounding of the power supply circuit unit 17 is connected to the connection terminal T13 which is the first ground terminal. The connection terminal T16 as the second ground terminal is provided for connecting the shield line CB6 that electromagnetically shields the communication line CB5. The connection terminal T13, which is the first ground terminal, and the connection terminal T16, which is the second ground terminal, are gap-coupled via a discharge gap (consisting of the gap arrester 18 in this embodiment).

  As a result, even when no shield wire is connected to the connection terminal T16 (the communication unit 15 is not grounded), when static electricity is applied to the connection terminal T15 or T16, the discharge gap becomes conductive, so that the first Static electricity can be released to the ground via the ground terminal. Therefore, the circuit components constituting the communication unit 15 can be protected from static electricity, and components having a low withstand voltage can be used for the circuit components constituting the communication unit 15, so that the cost can be reduced. In the present embodiment, a ground line for protective grounding of the power supply circuit unit 17 is connected to the connection terminal T13 which is a first ground terminal. However, the first ground terminal may be used for grounding the power measuring unit. . That is, it is only necessary that a ground line for protective grounding at least one of the power supply circuit unit 17 and the power measuring unit is connected to the first ground terminal, and the first ground terminal protects and grounds the high-voltage circuit. If it is for.

  Moreover, in this embodiment, the discharge gap is comprised by the gap arrester 18, and a discharge gap is realizable with components with favorable availability.

  Further, instead of configuring the discharge gap with the gap arrester 18, for example, the discharge gap may be configured with a pattern gap formed on the first circuit board B1, and the discharge gap can be realized at low cost. The pattern gap is a conductor pattern formed on the substrate so as to face each other with a predetermined interval, and detailed description thereof is omitted. The pattern gap may be formed on the second circuit board B2 on which the circuit including the communication unit 15 is mounted, and is formed on at least one of the first circuit board B1 and the second circuit board B2. The discharge gap may be configured by a pattern gap.

  Further, the power measuring instrument of the present embodiment includes a first circuit board B1 on which a circuit including a power measuring unit (consisting of a current measuring unit 11, a voltage measuring unit 12, and a power calculating unit 13) and a power supply circuit unit 17 is mounted. And a second circuit board B2 on which a circuit including the communication unit 15 is mounted. The container body 50 for housing the first circuit board B1 and the second circuit board B2 is configured by combining a body 51 and a cover 52. The first circuit board B1 is accommodated in one of the body 51 and the cover 52 (the body 51 in the present embodiment), and the second circuit board B2 is disposed in the other of the body 51 and the cover 52 (the cover 52 in the present embodiment). Is stored.

  Then, instead of the gap arrester 18, as shown in FIG. 7, the first circuit board B1 and the second circuit board B2 face each other with a predetermined gap in a state where the body 51 and the cover 52 are assembled. Conductive protrusions 23 and 24 may be provided. The protrusion 23 provided on the first circuit board B1 is electrically connected to the connection terminal T13 that is the first ground terminal via the wiring pattern 20. The protrusion 24 provided on the second circuit board B2 is electrically connected to the connection terminal T16 that is the second ground terminal via the wiring pattern 22. Thus, the connection terminal T13 as the first ground terminal and the connection terminal T16 as the second ground terminal are gap-coupled via the discharge gap formed by the protrusions 23 and 24.

  As a result, even when the shield wire is not connected to the connection terminal T16 (the communication unit 15 is not grounded), when static electricity is applied to the connection terminal T15 or T16, dielectric breakdown occurs between the protrusions 23.24. Thus, the protrusions 23 and 24 are electrically connected. Therefore, the static electricity applied to the communication unit 15 can be released from the first ground terminal to the ground, and the surge voltage and surge current applied to the circuit components constituting the communication unit 15 can be reduced. Therefore, it is possible to use a component having a low withstand voltage as the circuit component constituting the communication unit 15, so that the cost can be reduced.

  The gap length between the tip of the projection 23 and the tip of the projection 24 may be determined according to the voltage value or current value that causes dielectric breakdown between the projections 23 and 24.

1A Main unit 1B Extension unit 11 Current measurement unit (power measurement unit)
12 Voltage measurement unit (power measurement unit)
13 Power calculation unit (power measurement unit)
15 Communication section 17 Power supply circuit section 18 Gap arrester (discharge gap)
B1 First circuit board B2 Second circuit board CB5 Communication line CB6 Shield line T13 Connection terminal (first ground terminal)
T16 connection terminal (second ground terminal)
100 Management device (external device)

Claims (4)

A power measurement unit that measures power consumption by the load;
A communication unit that outputs a measurement result of the power measurement unit to an external device connected via a communication line;
A power supply circuit unit that receives power supply from an external power supply and supplies operating power to the power measurement unit and the communication unit;
A first ground terminal to which a ground line for protective grounding at least one of the power supply circuit unit and the power measuring unit is connected;
A second grounding terminal provided for connecting a shield wire for electromagnetically shielding the communication line;
A power measuring instrument, wherein the first ground terminal and the second ground terminal are gap-coupled via a discharge gap.   The power measuring instrument according to claim 1, wherein the discharge gap is a gap arrester. A first circuit board on which a high-power circuit including the power measuring unit and the power supply circuit unit is mounted;
A second circuit board on which a weak electric circuit including the communication unit is mounted,
The power measuring instrument according to claim 1, wherein the discharge gap is a pattern gap formed in one of the first circuit board and the second circuit board. A first circuit board on which a high-power circuit including the power measuring unit and the power supply circuit unit is mounted;
A second circuit board on which a weak electric circuit including the communication unit is mounted,
A container for housing the first circuit board and the second circuit board is configured by combining a body and a cover, and the first circuit board is housed in one of the body and the cover, and the body and the The second circuit board is housed in the other of the covers,
The first circuit board and the second circuit board are respectively provided with conductive protrusions facing each other with a predetermined gap in a state where the body and the cover are assembled.
The power measuring instrument according to claim 1, wherein the discharge gap is configured by the protrusion.

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