WO2010084251A1

WO2010084251A1 - Device for metering energy consumption and an electronic component and uses of the same

Info

Publication number: WO2010084251A1
Application number: PCT/FI2010/050041
Authority: WO
Inventors: Juha Lohvansuu
Original assignee: Aidon Oy
Priority date: 2009-01-26
Filing date: 2010-01-25
Publication date: 2010-07-29
Also published as: EP2391897A1; EP2391897A4; FI122736B; FI20095060A0; FI20095060A

Abstract

The invention relates to a device for metering energy consumption. The device includes connecting means (12) for connecting the device to the mains supply. In addition, the device includes metering equipment (13) connected to the connecting means (12) and switching means (14) for switching off the flow of electric current from the connecting means (12) to the metering equipment (13). The metering equipment (13) is adapted as galvanically separate from the connecting means (12). In addition, the metering equipment (13) is composed of a current transformer (18) with a primary current conductor (19) comprised therein being adapted as a part of a mains voltage part included in the switching means (14) for adapting at least part of the metering equipment (13) as one single electronic component with the switching means (14).

Description

DEVICE FOR METERING ENERGY CONSUMPTION AND AN ELECTRONIC COMPONENT AND USES OF THE SAME

The invention relates to a device for metering energy consump- tion, - the device including

- connecting means for connecting the device to the mains supply,

- metering equipment connected to the connecting means, and

- switching means for switching off the flow of electrical current from the connecting means to the metering equipment .

Besides the device, the invention also relates to an electronic component and uses of both .

FI patent No . 117075 proposes a current transformer for metering alternating current . The proposed current transformer is based on inductive current metering where alternating current to be metered is made to flow via a primary current conductor . Thus the current f lowing in the primary current conductor generates around it a magnetic field that changes as a function of time and place . In addition, located in the vicinity of the primary current conductor, there is a gradiometer to which the magnetic f ield induces a voltage comparable to the current flowing in the primary current conduct or . The output of a gradiometer , which is an element capable of detecting a magnetic field, provides a voltage signal comparable to the gradient of the magnetic field . Thus it is pos sible to meter the current flowing via the primary current conductor and thereby determine the energy consumption .

Energy consumption is metered in several different applications . As one common application, energy meters installed in the electric cabinets of real estates can be mentioned . Furthermore , the development tendency has been toward remote reading . In other words , energy meters are read via a wireless connection , a f ixed data network and/or even an electrical network. The energy meter and thus the electrical network of the real estate can be controlled as well. One control method is to place a remote-operated switch unit in the electric cabinet before the energy meter. Thus, if required, the elec- trical network of the real estate can be made currentless by the remote control as well.

The desired functions are thus provided by installing necessary equipment in the electric cabinet. However, equipment presently used requires a lot of installation space. For example, a known switch unit is almost of the same size as an energy meter. In other words, the type of equipment needed should be known already during the electrical engineering. Lack of space is a major problem particularly in retrofitting. Moreover, multiple devices create additional costs and the failure sensitivity of the equipment assembly increases. Problems appear also in known current transformers. For example, the mechanical construction between a primary current conductor and a gradiometer is often too weak. That is, the mechanical stability of the current transformer is poor. Thus, when the locations of the primary current conductor and the gradiometer change, the transformation ratio of the current transformer changes leading to an incorrect measurement of the energy meter.

The object of the invention is to provide a novel device for metering energy consumption that is smaller in size and more accurate and reliable than before. Another object of the invention is to provide a novel electronic component that is more versatile than before, yet more inexplensive to manufacture. The characteristic features of the device according to this invention become evident from the appended claim 1. Correspondingly, the characteristic features of the electronic component become evident from the appended claim 14. The operation of the device according to the invention is versatile. Nevertheless, the device is compact and maintains accuracy in spite of external stresses and disturbances. The electronic component accord- ing to the invention is also compact and can be used for switching higher currents than before. In addition, the mechanical stability of the electronic component is good, which is a precondition for an accurate and undisturbed operation of the device utilizing the electronic component.

The invention is described below in detail by making reference to the enclosed drawings, which illustrate some of the embodiments of the invention, in which

Figure Ia is a front view of a device according to the invention,

Figure Ib is a side view of the device of Figure Ia,

Figure Ic shows the device of Figure Ia with the cover removed,

Figure Id is a cross-sectional view of plane A-A of Figure Ic,

Figure 2a shows a drawing outlining the principle of an electronic component according to the invention,

Figure 2b shows a perspective view of an assembly composed of three electronic components according to the invention and a part of one primary current conductor,

Figure 3a is a cross-sectional view of an electronic component according to the invention,

Figure 3b shows a part of the components of the electronic component according to Figure 3a seen from direction A.

Figures la-Id illustrate the principle of an energy meter which is a device according to the invention for metering energy consumption. Here the device is designed for metering three- phase alternating current. Such an energy meter is placed in an electric cabinet of a real estate, for example, and connected between the electrical network of the real estate and an external electrical network that supplies electricity. The energy consumed in the real estate can then be metered for the purpose of invoicing, for example.

Generally the device includes some kind of a case 10 and a detachable and openable cover 11, which in practice are sealed, mainly for preventing abuse. As functional parts, the device includes connecting means 12 for connecting the device to the mains supply. It is usually strived to standardize the form and dimensioning of the connecting means such that the device can be installed without problems in different countries and to different electric armature. In addition, the device includes metering equipment 13 connected to the connecting means 12 the purpose of which is to meter, either directly or indirectly, the energy flowing via the device. The device further includes switching means 14 for switching off the flow of the electric current from the connecting means 12 to the metering equipment 13. Thus the device and thereby the real estate can be made currentless, that is, disconnected from the load or de-energized. According to the invention, the metering equipment 13 is adapted as galvanically separate from the connecting means 12. In addition, the metering equipment 13 is composed of a current transformer 18 with a primary current conductor 19 comprised therein being adapted as a part of a mains voltage part included in the switching means 14 for adapting at least part of the metering equipment 13 as one single electronic component with the switching means 14 (Figures 2, 3a and 3b) . Firstly, a significant space saving can be achieved with the proposed integration. Secondly, the mechanical stability of the metering equipment and of the switching means can be made good. An electronic component according to the invention is also compact. Besides the space saving, galvanic separation has a great significance for electric safety and measuring technique as well as for corrosion prevention. Galvanic separation prevents the flow of direct current between electric circuits at differ- ent potentials and restricts the circulation of undesired direct currents in the system. In addition to the above mentioned part s , the case 10 also contains a computing and control card 15 for proces sing the signals received from the metering equipment . The computing and control card 15 has usually also buttons and a display device for using and controlling the device (not shown) . A device that is remotely readable and usable has additionally one or more telecommunication connections . Here , too, galvanic separation is useful because the current transformer can provide a potential-free voltage message as a signal and this message can be entered directly to the computing and control card .

Figure 2a illustrates the principle of one electronic component according to the invention including connecting elements 16 for connecting the electronic component to a device that includes measuring equipment 13 for metering energy consumption . The electronic component additionally includes coupling means 17 for switching of f the flow of electric current between the connecting means 16 . According to the invention , when the metering equipment 13 is composed of a current transformer 18 , the primary current conductor 19 included in the current transformer 18 is adapted as galvanically separate from the connecting elements 16 and arranged as a part of the mains voltage part included in the connecting elements 16 for adapting at least part of the metering equipment 13 as one single elec- tronic component with the coupling means 17 . Thus two functions can be arranged as one electronic component , which brings significant savings in manufacturing costs and in the installation space requirement . At the same time , both the coupling means and the metering equipment can be made mechanical ly stable while adapting their operation optimal relative to each other . Thus the electronic component can be easily adapted in an energy meter, for example, without worry about the accuracy of the device operation impairing due to both installation errors and external disturbances . Galvanic separation also increases electrical safety and reduces disturbances . According to the invention, the metering equipment 13 is thus composed of a current transformer 18 with the primary current conductor 19 comprised therein being adapted as a part of the switching means 14, particularly as its mains voltage part. A current transformer is a relatively simple component and its parts are surprisingly well suitable to be placed as a part of another electronic component. In addition, a current transformer functions well particularly in the current ranges of energy meter applications. In practice, a current transformer functions even with low currents but, on the other hand, also endures high voltages without heating up. In electrical networks designed for consumers the mains voltage is usually 110 or 230 volts. For example, an electronic component that is installed in a mains voltage of 230 volts is dimensioned for a maximum current of 80 amperes, which is taken into account in the dimensioning of the mains voltage parts of the electronic component. Generally, the mains voltage part is connected to mains voltage. According to the invention, the metering equipment is, however, galvanically separated from the mains voltage in which case it is potential-free.

As a switch device to be integrated with the current transformer, a relay has been found to be surprisingly good. A relay is small in size and the disturbing effect of the electromag- netic substance contained in the relay can be compensated either structurally or computationally. On the other hand, according to the invention, the relay 20 can be adapted as an amplifier for the current transformer 18. Thus the current transformer and the relay are co-operating, which increases the accuracy of energy metering. Tests have shown that amplification has a significant effect. In the relay, a current impulse led to the coil generates a magnetic field that moves the contactor. Advantageously, an impulse relay, also referred to as a side-stable relay, is used. This relay is bistable, which means that it maintains its position when the coil is de-energized and changes its position only after receiving the current impulse. As a functional current transformer, a converter can be used, for example.

In Figure 2a, the input 21 included in the relay 20 is arranged as a part of the primary current conductor 19 of the current transformer 18. In other words, current flowing via the relay simultaneously flows via the primary current conductor. In this case the electronic component contains even substantially less copper used in the conductors than before, which allows using a higher current as the resistance has reduced. Therefore, the maximum rated current of a relay with a present size can be increased by several tens of percentages. Deviating from the proposed, instead of a relay input, a relay output can be arranged as a part of the primary current conductor (not shown) . The integration can be taken even further by arranging the mains voltage part of the coupling means as the primary current conductor of the current transformer. That is, the relay input and the primary current conductor, for example, can be of one and the same part. Thus one part has two different functions. Even the connector pin included in the relay can be arranged in the primary current conductor. In this case, for example, the relay includes only two mains voltage parts of copper, such as an input and output of the primary current circuit, wherein one of these has the moving tongue of the relay connected thereto and another one has the connector pin attached to it (not shown) . Such a solution reduces the need of copper and facilitates manufacture. At the same time, the number of required connections decreases. For example, the primary current conductor 19 shown in Figure 2b is thus inte- grated to the input 21 whereby the construction of the relay simplifies further. In one advantageous application, the primary current conductor is of the same material as the mains voltage part of the coupling means. This simplifies the manufacture, and the dimensioning of the mains voltage part can be utilized in the dimensioning of the primary current conductor. The application of Figure 2b mainly illustrates the application of the invention in existing relays. In addition to the integration proposed in the preceding paragraph, the design of the novel relay can be renewed. For example, the relay is manufac- tured with two parts wherein the first part comprises, for example, the relay output and the coil that uses the contactor of the relay. The relay input together with a gradiometer is then connected to the second part. In this case separate support blocks 26 and magnetic iron plates 33 of Figure 2b are unnecessary, which further reduces the size of the relay.

Figure 3a shows a more detailed view of the electronic component according to the invention. The view is not cross-sectional for all parts although line patterns indicating cross-sec- tions are used. Also, Figure 3a does not show insulations between various parts or other auxiliary and support constructions. The most part of the electronic component is formed by the relay 20, the frame 23 of which is represented by sparse diagonal lines. For clarity, the internal construction of the relay is not shown. In the application shown, the primary current conductor 19 is mechanically connected to the relay 20, generally to the coupling means, and it is galvanically joined to the input 21 of the relay 20. In addition, a gradiometer included in the current transformer is formed on the circuit board 24, which is arranged as a part of the switching means 14. The principle of the gradiometer 25 is shown with a broken line in Figure 2a. In the application of Figure 3a, first the above mentioned circuit board 24 and then the primary current conductor 19 are adapted against the frame 23 of the relay 20. Various parts are additionally supported with a plastic support block 26 that is designed to be connected to the frame 23 of the relay 20. Then the different parts are ensured to be held in the desired place without the possibility of them to move. Thus an electronic component that is systematically manufac- tured and tuned up maintains its accuracy. In Figures 3a and 3b, the circuit board 24 is represented by dense horizontal lines and the primary current conductor 19 by medium-dense diagonal lines. The support block 26 is represented by sparse double lines and the terminal 27 connected to the primary current conductor 19 by dense double lines. A screw included in the terminal is not shown. In practice, the screw is used to push a conductor inserted into the terminal securely against the relay input. A corresponding terminal 28 is located in the relay output. The relay itself, more generally the electronic component, is connected to the casing of an energy meter, for example, with a form-lock or with separate fasteners.

Figure 3b shows only the frame 23 of the relay 20, the circuit board 24 and a part of the primary current conductor 19 as well as the terminal 27. The positions of the holes 29 are also indicated in Figure 3b. Corresponding holes are present in almost all parts, and the bolts or similar that placed in these holes during the assembly firstly align various parts relative to each other as designed and, on the other hand, press the parts securely against each other. In Figure 3a the bolting line is represented by a dot-and-dash line, and the nuts 31 connected to the bolts 30 are shown in Figure 2b. The number and locations of bolts or other similar fasteners can vary in different applications. Instead of a relay formed by a coil and a contactor, other types of switching means can also be used. For example, an electronic component exists containing three contactors in which one electric motor moves all three contactors simultaneously.

Deviating from the proposed, the primary current conductor can be cast to the frame of the relay, more generally of the switching means, for example. Thus the primary current conductor is readily and accurately aligned relative to the relay. At the same time, it is advantageous that the circuit board is placed on the side of the primary current conductor, against the frame of the relay. In this case the circuit board can be cast to the frame of the relay, more generally of the switching means, to be connected to the intended support block. With this solution, it is sufficient during the assembly that two different parts are aligned relative to each other, which facilitates the manufacture. At the same time, gluing, for example, can be 5 used for connecting.

The device according to the invention includes one electronic component per each electrical network phase to be metered, arranged as one single assembly. Advantageously, the device 0 includes three similar electronic components arranged as one assembly for metering a three-phase electrical network separately for each phase. A three-phase electrical network is the most commonly used technique globally. An assembly manufactured for metering three phases is shown in Figure 2b. In addition to

15 the above mentioned parts, an electromagnetic protective structure 32 is illustrated, arranged around the assembly, for insulating the electronic component from both the environment and other electronic components of the assembly. In this way, for example, crosstalk of various phases to the current trans-

20 former is avoided. The protective structure is formed of magnetic iron plates 33, which are placed suitably around and between the electronic components. Figure 3a shows one L-shaped protective plate and one straight protective plate, represented by dense diagonal lines. In Figure 2b, conductors 34 for using

25 the relay are also illustrated. Correspondingly, Figure 3b shows a pair of conductors 35, made of a coaxial cable or a shielded twisted pair cable, departing from the circuit board 24. In this way it is possible to avoid disturbances caused by the conductors themselves to the voltage signal of the gradiom-

30 eter. The conductors are connected to the computing and control card for processing. If necessary, a specific control card or another suitable means is used for the current transformer. It is also possible to arrange a part of the components 36 and/or functionality of the metering equipment 13 on the circuit board

35 24. Then a signal processed in some way is received from the circuit board, in which case the computing and control card can be made simpler than before.

Figure 2b also shows one continuous part of the assembly formed by the primary current conductor and a part of the relay input. Such a part can be even connected to a relay, conventional as such, adding subsequently the circuit board comprising the gradiometer for forming the electronic component according to the invention. The use of such an electronic component is advantageous in metering energy consumption. Besides energy metering, the electronic component provides load disconnection, in which case the use of a device equipped with the electronic component for metering energy consumption is advantageous. When the electronic component is completely redesigned, it is advan- tageous to manufacture the assembly formed by the primary current conductor and the relay input as one piece, avoiding in this way a solder joint required in the application of Figure 2b.

The design of the gradiometer to be formed on the circuit board can be freely selected from the known technique as long as it can be tuned up to operate in the novel electronic component. For example, it is possible to use a first-order gradiometer formed on one layer of the circuit board or a second-order or higher gradiometer formed on more layers . The higher the order of the gradiometer used, the better it attenuates external magnetic fields. However, at the same time it attenuates the magnetic field generated by the primary current conductor.

With the proposed design and particularly by the positioning, it is possible to use a primary current conductor that is more complex than before, which allows obtaining an alternating current higher than before in the current transformer. At the same time, the size of the current transformer can be dimensio- ned based on the signal-to-noise ratio instead of standardized connecting means of energy meters. An electronic component is also inexpensive to manufacture and the other dimensions of the device can be kept unchanged. In practice, an electronic component according to the invention equipped with switching means is as small as a mere conventional relay or another correspond- ing functional component. Thus the size of the device is constant although its characteristics are different. The electronic component is as such a single compact integral package containing a small amount of copper. The electronic component is also stable and accurate and it operates in a wide current and voltage range because the internal consumption of the electronic component is constant. At the same time, the design of electronics is simple. Furthermore, double insulation can be achieved with the electronic component. Firstly, the metering equipment is galvanically separated from the load to be me- tered. Secondly, each phase is separated from one another. Thus the electronic component functions accurately and free of disturbances .

Claims

CIAIMS

1. Device for metering energy consumption, the device including - connecting means (12) for connecting the device to the mains supply,

- metering equipment (13) connected to the connecting means

(12), and

- switching means (14) for switching off the flow of the electric current from the connecting means (12) to the metering equipment (13) , characterized in that the metering equipment (13) is adapted as galvanically separate from the connecting means (12) , and the metering equipment (13) is composed of a current transformer (18) , with the primary current conductor (19) comprised therein being adapted as a part of a mains voltage part included in the switching means (14) for adapting at least part of the metering equipment (13) as one single electronic component with the switching means (14) .

2. Device according to claim 1, characterized in that the switching means (14) include, as mains voltage means, an input (21) and an output (22) , of which one is arranged as a part of the primary current conductor (19) of the current transformer (18) .

3. Device according to claim 1 or 2, characterized in that the primary current conductor (19) is of the same material as the mains voltage part of the switching means (14) .

4. Device according to any of claims 1 - 3, characterized in that the mains voltage part of the switching means (14) is arranged as the primary current conductor (19) of the current transformer (18) .

5. Device according to any of claims 1 - 4, characterized in that the primary current conductor (19) is mechanically connected to the switching means (14).

5 6. Device according to any of claims 1 - 5, characterized in that the primary current conductor (19) is cast in the frame

(23) of the switching means (14) .

7. Device according to any of claims 1 - 6, characterized 10 in that the switching means (14) include a relay (20) .

8. Device according to claim 7, characterized in that the relay (20) is adapted as an amplifier for a current transformer (18) .

15

9. Device according to any of claims 1 - 8, characterized in that a gradiometer (25) included in the current transformer (18) is formed on a circuit board (24), which is arranged as a part of the switching means (14) . 20

10. Device according to claim 9, characterized in that the circuit board (24) is cast to a support block (26) designed to be connected to the switching means (14) .

25 11. Device according to claim 9 or 10, characterized in that part of the components (36) and/or the functionality of the metering equipment (13) is arranged on the circuit board

( 24 ) .

30 12 . Device according to any of claims 1 - 11 , characteri z ed in that the device includes three s imilar electronic components arranged as one assembly for metering a three-phase electrical network separately for each phase .

35 13 . Device according to claim 12 , characterized in that an electromagnetic protective structure ( 32 ) is arranged around the assembly for insulating the electronic component from both the environment and other electronic components of the assembly.

5 14. Electronic component including

- connecting elements (16) for connecting the electronic component to a device that includes metering equipment (13) for metering energy consumption, and

- coupling means (17) for switching off the flow of electri- 10 cal current between the connecting elements (16) , characterized in that, when the metering equipment (13) is composed of a current transformer (18) , a primary current conductor (19) comprised in the current transformer (18) is adapted as galvanically separate from the connecting elements 15 (16) and arranged as a part of a mains voltage part included in the connecting elements (16) for adapting at least part of the metering equipment (13) as one single electronic component with the coupling means (17) .

20 15. Electronic component according to claim 14, characterized in that a part of the metering equipment (13) is a primary current conductor (19) according to any of claims 2 - 6.

16. Electronic component according to claim 14 or 15, 25 characterized in that the electronic component is a relay adapted as an amplifier for the current transformer (18) .

17. Electronic component according to any of claims 14 - 16, characterized in that a circuit board (24) is arranged as

30 a part of the coupling means (17) onto which a gradiometer (25) included in the current transformer (18) is formed.

18. Use of an electronic component according to any of claims 14 - 17 for metering energy consumption.

35

19. Use of a device according to any of claims 1 - 13 for metering energy consumption.