CN201011520Y - Three-phase electric energy meter - Google Patents

Three-phase electric energy meter Download PDF

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Publication number
CN201011520Y
CN201011520Y CNU2007200030110U CN200720003011U CN201011520Y CN 201011520 Y CN201011520 Y CN 201011520Y CN U2007200030110 U CNU2007200030110 U CN U2007200030110U CN 200720003011 U CN200720003011 U CN 200720003011U CN 201011520 Y CN201011520 Y CN 201011520Y
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CN
China
Prior art keywords
electric energy
voltage
current
phase
energy meter
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CNU2007200030110U
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Chinese (zh)
Inventor
瞿清昌
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北京双目佳测控技术有限责任公司
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Priority to CNU2007200030110U priority Critical patent/CN201011520Y/en
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Publication of CN201011520Y publication Critical patent/CN201011520Y/en

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Abstract

The utility model discloses an electric measuring device, in particular to a three phase electric energy meter which detects the cable current and voltage of each phase respectively through an electricity current control detecting unit and a voltage detecting unit. And the cable current and voltage of each phase are jointly transmitted into an electric energy measuring and computing unit, and further the electricity is accumulatively computed by the electric energy measuring and computing unit. Under the circumstance of without increasing the cost on hardware, the principle deviation caused by the outbalance of a three phase loaded electric current can be avoided to greatly improve the accuracy of the measured and computed results. In addition, through adopting and detecting the electricity current modes acting on a voltage divider, the measure on the cable voltage is realized. Without using a voltage transformer, the electric energy meter not only has relatively high complexity but also further reduces the measuring and computing accuracy of the electric energy of a high voltage cable line. Therefore, the utility model can be better used in the electric detecting operation of a high voltage electric network.

Description

Three-phase electric energy meter
Technical field
The utility model relates to a kind of power measurement device, particularly a kind of three-phase electric energy meter.
Technical background
Electric energy is the most basic energy that uses in the national economy, and the electric energy industry accounts for more than 10% in total value of production in national economy GDP.Electric energy is a kind of commodity of instant generating and using, and annual generating total amount surpasses 2,000,000,000,000 kilowatt hours in China, and all immediately by customer consumption, the user power utilization amount is measured by electric energy meter.Residential electricity consumption uses the single-phase electric energy meter metering by single phase power supply, and resident's consumption accounts for 10% of total electric weight greatly.Account for large users such as the industrial and mineral of delivery more than 90%, enterprise, public institution and all adopt three phase supply, so three-phase electric energy meter is a most important electric energy metering device in the electricity consumption clearing.Some big users also need high voltage supply, also have the electric weight clearing between electrical production, electric power transfer enterprise simultaneously, need the network interface high-voltage electric energy meter of high pressure.
Traditional three-phase electric energy meter has two big classes: a class is a three-phase four-wire system, and a class is a three-phase three-wire system.
The principle of three-phase electric energy meter as shown in fig. 1 in the typical three-phase four-wire system electrical network.In fact the three-phase and four-line electric energy meter is made up of three W1 of electric energy metrical mechanism, W2, W3 that are separately positioned between A, B, C three-phase and the ground wire N, measure the power consumption of three-phase respectively, electric current, two branch roads of voltage are all forgiven by each electric energy metrical mechanism, and its mathematical expression is:
P Σ = P W 1 + P W 2 + P W 3 = 1 T ∫ 0 T u A i A dt + 1 T ∫ 0 T u B i B dt + 1 T ∫ 0 T u C i C dt - - - ( 1 )
In the formula: P Be three-phase general power (electric energy is the integration of power, and promptly electric power adds up);
P W1, P W2, P W3Be three power measurement results of power measurement mechanism;
u A, u B, u CBe phase voltage, promptly every phase firewire center line () voltage;
i A, i B, i CElectricity consumption electric current for each phase.
The metering result of three-phase four-wire system electric energy meter is accurate, but needs to introduce the ground wire (center line) of electrical network, so measurement structure is comparatively complicated.
Electric energy meter schematic diagram in the three-phase three-wire system electrical network as shown in Figure 2.Obviously, at this moment measure three-phase electric energy and only need two W of electric energy metrical mechanism 1, W 2, different just W 1, W 2The voltage branch road respectively cross-over connection between A-B, C-B, three-phase electric energy list structure and wiring have all been simplified greatly, be an important simplification of three-phase and four-line electric energy meter, be the threephase load symmetry on its pacing items, that is:
i A+i B+i C=0????(2)
Then have
i B=-i A-i C?????(3)
(1) formula just can be reduced to like this
P Σ = 1 T ∫ 0 T ( u A - u B ) i A dt + 1 T ∫ 0 T ( u C - u B ) i C dt
= 1 T ∫ 0 T u AB i A dt + 1 T ∫ 0 T u CB i C dt - - - ( 4 )
So three-phase three-wire electric energy meter has obtained using widely.
Problem is that the condition of (2) formula can not satisfy under normal conditions, and there is one in threephase load and departs from Δ i, that is: i under essentially identical situation A+ i B+ i C=Δ i (5)
The correct expression of (4) formula should be like this
P ΣB = 1 T ∫ 0 T u AB i A dt + 1 T ∫ 0 T u CB i C dt + 1 T ∫ 0 T u B Δidt - - - ( 6 )
(6) one at end is exactly the error of three-phase three-wire electric energy meter measurement result in the formula.The three-phase three-wire system electric energy meter only need be introduced three live wires, and is simple in structure, but there is original reason error when uneven in threephase load.
And, present three-phase electric energy meter all can't be directly used in high pressure, it will be converted to low pressure (100V) with high pressure by voltage transformer (VT) (PT), it will become little electric current (5A or 1A) by current transformer (CT) with big electric current with big electric current, not only improve the complicacy and the cost of structure, also can't realize whole measurement and calibration and calibrating simultaneously.
The utility model content
The utility model has overcome above-mentioned shortcoming, a kind of accurate measurement is provided, can be used for the three-phase electric energy meter that high-tension line is measured.
The technical scheme in the invention for solving the technical problem is: a kind of three-phase electric energy meter comprises
Current detecting unit is used to detect the line current of place circuit;
Voltage detection unit is used to detect alternate in twos line voltage;
Electric energy is calculated the unit, receives the testing result of each current detecting unit and voltage detection unit, calculates the accumulative total electric energy.
Described voltage detection unit can be and is connected across two alternate voltage/voltage changers, with detected line voltage signal, outputs in the described electric energy measuring and calculating unit.
Described voltage detection unit can comprise that cross-over connection two is alternate, and voltage divider that is connected in series and current/voltage transducer with the current signal in the detected series circuit, output in the described electric energy measuring and calculating unit.
Described voltage divider can be made of the divider resistance of a plurality of series connection.
Described divider resistance is outer around a plurality of conducting rings that connected by electric capacity can be arranged.
The output terminal of described conducting ring can be connected with a power supply unit, and the current conversion that described conducting ring is exported is direct supply output.
Described current detecting unit can comprise the current/voltage transducer that is connected in the circuit of place, and detected line current is converted to voltage signal, outputs in the described electric energy measuring and calculating unit.
Described electric energy measuring and calculating unit can comprise
The A/D modular converter with the testing result of current detecting unit and voltage detection unit, changes through analog/digital signal, is converted into the A/D level signal;
Power computation module calculates performance number according to described A/D level signal;
Numeral/frequency translation module is transformed to the performance number that calculates the pulse of corresponding frequencies;
Electric energy accumulative total module adds up to obtain energy value with above-mentioned pulse signal.
The utility model passes through current detecting unit, voltage detection unit detects respectively and obtains accurate ratio in the line current and the line voltage signal of each phase, unified again being sent in the described electric energy measuring and calculating unit, carry out the electric energy cumulative calculation by described electric energy measuring and calculating unit, do not improving under the prerequisite of hardware cost, the original reason error that elimination is caused by the threephase load current imbalance, greatly improved the accuracy of results of measuring, in addition, adopt the mode of the electric current of detection effect on voltage divider, realization is to the measurement of line voltage, can need not the working voltage mutual inductor, make electric energy meter itself not only have lower complexity, also further improve the accuracy of high-tension line electric energy measuring and calculating, can in the electric energy detection of high-voltage fence, obtain better application.
Description of drawings
Fig. 1 is the structural representation of three-phase four-wire system electric energy meter in the prior art;
Fig. 2 is the structural representation of three-phase three-wire system electric energy meter in the prior art;
Fig. 3 is the structural representation of the utility model embodiment one;
Fig. 4 is the structural representation of the utility model embodiment two.
Embodiment
As shown in Figure 3, be the structural representation of a kind of preferred embodiment of the present utility model, present embodiment is for being applicable to line voltage 380V, 10kV, 35kV, the novel three-phase three-wire electric energy meter of phase current 0-1000A, the line current i in the three-phase A, i B, i CRespectively by be connected in the place circuit separately current/voltage transducer (hereinafter to be referred as the I/V transducer) I/V 1., I/V 2., 3. I/V realize measuring, and detected current signal is converted to voltage signal, output in the described electric energy measuring and calculating unit.And three line voltage u AB, u BC, u CABy be connected across per two alternate voltage/voltage changer (hereinafter to be referred as the V/V transducer) V/V 4., V/V 5., V/V 6., detected voltage signal also outputs in the described electric energy measuring and calculating unit.Three-route voltage signal and three-route current signal act on electric energy measuring and calculating unit M input end 7. simultaneously, described electric energy measuring and calculating unit, with receive above-mentioned by I/V 1., I/V 2., I/V 3., V/V 4., V/V 5., the simulating signal that 6. measures of V/V is through the A/D conversion, be converted into the A/D level signal, according to the described mathematical expression of B phase three-phase three-wire electric energy meter altogether of above-mentioned (6) formula, can obtain common C and be respectively with the mathematical expression that is total to A three-phase three-wire electric energy meter mutually mutually:
P ΣC = 1 T ∫ 0 T u AC i A dt + 1 T ∫ 0 T u BC i B dt + 1 T ∫ 0 T u C Δidt - - - ( 7 )
P ΣA = 1 T ∫ 0 T u BA i B dt + 1 T ∫ 0 T u CA i C dt + 1 T ∫ 0 T u A Δidt - - - ( 8 )
If get the mean value of (6), (7), (8) formula, then the total power of three-phase is:
P Σ = 1 3 ( P ΣA + P ΣB + P ΣC ) - - - ( 9 )
= 1 3 ( 1 T ∫ 0 T u BA i B dt + 1 T ∫ 0 T u CA i C dt + 1 T ∫ 0 T u AB i A dt + 1 T ∫ 0 T u CB i C dt
+ 1 T ∫ 0 T u AC i A dt + 1 T ∫ 0 T u BC i B dt )
+ 1 3 1 T ∫ 0 T ( u A + u B + u C ) Δidt - - - ( 10 )
(10) last item is the error term of above-mentioned measurement result in the formula, the symmetry of considering three-phase voltage promptly:
u A+u B+u C=Δu????(11)
(10) error term in the formula becomes:
ΔP= 1 3 1 T ∫ 0 T ΔuΔidt - - - ( 12 )
Obviously Δ P compares with the error in (6) formula and greatly reduces, and normal conditions are issued to negligible degree.
Therefore the total power P by above-mentioned measurements and calculations acquisition , it is the pulse of corresponding frequencies that numeral/frequency translation module (hereinafter to be referred as the D/F conversion) will calculate the Power Conversion that obtains; Obtain energy value by accumulative total at last to above-mentioned pulse signal.The computed in software that above-mentioned measuring and calculating, D/F conversion and accumulative total process also can be passed through in computing machine, the chip obtains, wherein u AB=-u BA, u BC=-u CB, u AC=-u CA
From present embodiment as can be seen, the three-phase electric energy meter that the utility model provides, its hardware cost and existing three-phase and four-line electric energy meter do not have too big difference, but it has realized a kind of three-phase three-wire electric energy meter that does not have original reason error, from the outside, its circuit connects also simple equally with existing three-phase three-wire electric energy meter, so the promotion and application ratio is easier to.
Another kind of embodiment of the present utility model provides a kind of network interface phase three-wire three high-voltage electric energy meter, is the structural representation of present embodiment as shown in Figure 4.
In order to ensure safety, network interface three-phase high-voltage electric energy table is by three measuring mechanism W 1, W 2, W 3Constitute, its structure is identical, so only with the W of A phase 1For example is illustrated.W 1Be positioned at electrical network A phase port, the electric energy transmitting direction is by A → A ' (anti-phase then electric energy is a negative value), A phase line current i A1. I/V measures by the I/V transducer, with ratio in i AVoltage signal output in the electric energy measuring and calculating unit M input channel 4.; Described A, B two are alternate, are in series with voltage divider R AWith I/V transducer I/V 3., R AIn electric current flow through I/V and 3. produce ratio in U ABVoltage, therefore by detected and voltage divider R ACurrent conversion in the series circuit is a voltage signal, output to described electric energy measuring and calculating unit M 4. in; In like manner, the line voltage that described A, C two are alternate passes through measure R CIn electric current flow through I/V and 2. produce ratio in U ACVoltage, also output to described electric energy measuring and calculating unit M 4. in.Described voltage divider is made of the divider resistance of a plurality of series connection, with being perfectly safe of the voltage of guaranteeing each divider resistance and power consumption.Described divider resistance is surrounded with a plurality of conducting rings that connect with electric capacity outward and constitutes another alternate capacitance partial pressure branch road, forms the equivalent potential screen mechanism of a mouse cage shape, to guarantee the accurate and anti-interference of electric resistance partial pressure.The capacitance partial pressure branch road C that described conducting ring constitutes A, C CElectric current (representative value is 2mA), through S P5. collect and handle, be converted to direct supply output, be W 1Internal current provides direct current supply.
Described electric energy measuring and calculating unit M 4. hardware configuration and a three-phase three-wire electric energy meter chip is basic identical, and carries out following calculating
P W 1 = 1 T ∫ 0 T u AC i A dt + 1 T ∫ 0 T u AB i A dt - - - ( 13 )
In like manner:
P W 2 = 1 T ∫ 0 T u BA i B dt + 1 T ∫ 0 T u BC i B dt - - - ( 14 )
P W 3 = 1 T ∫ 0 T u CA i C dt + 1 T ∫ 0 T u CB i C dt - - - ( 15 )
The measurement result phase adduction of above-mentioned three measuring mechanisms is obtained divided by 3
P Σ = 1 3 ( P W 1 + P W 2 P W 3 )
= 1 3 ( 1 T ∫ 0 T u AC i A dt + 1 T ∫ 0 T u AB i A dt + 1 T ∫ 0 T u BA i B dt + 1 T ∫ 0 T u BC i B dt
+ 1 T ∫ 0 T u CA i C dt + 1 T ∫ 0 T u CB i C dt ) - - - ( 16 )
This is the three phase electric energy measurement result of (10) formula in the foregoing description one, and it is different with the order of (6)-(10) formula, but synthetic result is the same.
In the present embodiment, W 1, W 2, W 3Three measuring mechanisms are selected A respectively, and B, three ports of C be as the reference point of electricity, simultaneously W 1, W 2, W 3All be arranged in the shielding body of an electricity and heat to guarantee safety at the corresponding levels and stable.Because present embodiment is applied to the measurement of high voltage electric energy; therefore need be with 4. separately the line voltage and the line current result of measurement of electric energy measuring and calculating unit M in each measuring mechanism; 6. send to ground by carrier chip T; receive by the ground carrier system; do further data processing in another electric energy measuring and calculating unit that is sent to again; 4. the result who is 6. sent out by described carrier chip T by electric energy measuring and calculating unit M is regardless of and is limited to electric energy, can also comprise electric current, voltage and guard signal etc.Therefore present embodiment can obtain better application in the electric energy measuring and calculating in high-tension line, and (10kV 35kV) in the electric energy metrical cabinet, or is applied to make in the three-phase three-wire electric energy meter of electrical network high pressure (110kV is more than 220kV reaches) for example to be applied to the distribution high pressure.
In addition, described current/voltage transducer can also adopt current transformer CT to add the resistance sampling and substitute realization, and described voltage/voltage changer also can adopt voltage transformer pt to substitute realization.
More than three-phase electric energy meter provided by the utility model is described in detail, used specific case herein principle of the present utility model and embodiment are set forth, the explanation of above embodiment just is used for helping to understand method of the present utility model and core concept thereof; Simultaneously, for one of ordinary skill in the art, according to thought of the present utility model, the part that all can change in specific embodiments and applications, in sum, this description should not be construed as restriction of the present utility model.

Claims (8)

1. a three-phase electric energy meter is characterized in that: comprise
Current detecting unit is used to detect the line current of place circuit;
Voltage detection unit is used to detect alternate in twos line voltage;
Electric energy is calculated the unit, receives the testing result of each current detecting unit and voltage detection unit, calculates the accumulative total electric energy.
2. according to the three-phase electric energy meter of claim 1, it is characterized in that: described voltage detection unit is to be connected across two alternate voltage/voltage changers, with detected line voltage signal, outputs in the described electric energy measuring and calculating unit.
3. three-phase electric energy meter according to claim 1, it is characterized in that: described voltage detection unit comprises that cross-over connection two is alternate, voltage divider that is connected in series and current/voltage transducer with the current signal in the detected series circuit, output in the described electric energy measuring and calculating unit.
4. three-phase electric energy meter according to claim 3 is characterized in that: described voltage divider is made of the divider resistance of a plurality of series connection.
5. three-phase electric energy meter according to claim 4 is characterized in that: described divider resistance is surrounded with a plurality of conducting rings that connected by electric capacity outward.
6. three-phase electric energy meter according to claim 5 is characterized in that: the output terminal of described conducting ring is connected with a power supply unit, and the current conversion that described conducting ring is exported is direct supply output.
7. according to each described three-phase electric energy meter in the claim 1~6, it is characterized in that: described current detecting unit comprises the current/voltage transducer that is connected in the circuit of place, detected line current is converted to the A/D level signal, outputs in the described electric energy measuring and calculating unit.
8. according to each described three-phase electric energy meter in the claim 1~6, it is characterized in that: described electric energy measuring and calculating unit comprises
The A/D modular converter with the testing result of current detecting unit and voltage detection unit, changes through analog/digital signal, is converted into the A/D level signal;
Power computation module calculates performance number according to described A/D level signal;
Numeral/frequency translation module is transformed to the performance number that calculates the pulse of corresponding frequencies;
Electric energy accumulative total module adds up to obtain energy value with above-mentioned pulse signal.
CNU2007200030110U 2007-01-29 2007-01-29 Three-phase electric energy meter CN201011520Y (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010081280A1 (en) * 2009-01-13 2010-07-22 中国计量科学研究院 Three-phase electric energy measurement apparatus
CN104049117B (en) * 2014-07-02 2017-04-12 重庆华虹仪表有限公司 Two-phase three-line dual-voltage alternating current watt-hour meter

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010081280A1 (en) * 2009-01-13 2010-07-22 中国计量科学研究院 Three-phase electric energy measurement apparatus
CN101458277B (en) * 2009-01-13 2011-02-09 中国计量科学研究院 Three phase electric energy measurement apparatus
AU2009337631B2 (en) * 2009-01-13 2013-07-25 National Institute Of Metrology P. R.China Three-phase electric energy measurement apparatus
US8823359B2 (en) 2009-01-13 2014-09-02 National Institute Of Metrology P.R. China Three-phase electric energy measurement apparatus
CN104049117B (en) * 2014-07-02 2017-04-12 重庆华虹仪表有限公司 Two-phase three-line dual-voltage alternating current watt-hour meter

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