CN201011520Y - Three-phase electric energy meter - Google Patents
Three-phase electric energy meter Download PDFInfo
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- 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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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
Technical Field
The utility model relates to an electric power measuring device, especially a three-phase electric energy meter.
Technical Field
Electric energy is the most basic energy used in national economy, and the electric energy industry accounts for more than 10% of the total output value GDP of the national economy. The electric energy is a commodity which can be used instantly, the total amount of electricity generation in China exceeds 2 trillion kilowatts per year, the electricity is consumed by users instantly, and the electricity consumption of the users is measured by an electric energy meter. The electricity consumption of residents is measured by a single-phase electric energy meter supplied by single phase, and the consumption of the residents accounts for about 10% of the total electricity. Large users such as industrial and mining, enterprises and public institutions, which account for more than 90% of the power supply, all adopt three-phase power supply, so that the three-phase electric energy meter is the most important electric energy metering appliance in electricity consumption settlement. Some large users also need high-voltage power supply, and meanwhile, electric quantity settlement between power generation enterprises and power transmission enterprises also exists, and a higher-voltage network port high-voltage electric energy meter is needed.
The traditional three-phase electric energy meter has two main types: one is a three-phase four-wire system and the other is a three-phase three-wire system.
The principle of a typical three-phase electric energy meter in a three-phase four-wire system grid is shown in fig. 1. The three-phase four-wire electric energy meter is actually composed of three electric energy metering mechanisms W1, W2 and W3 which are respectively arranged between A, B, C three phases and a ground wire N, the three phases of electricity consumption are respectively metered, each electric energy metering mechanism comprises two branches of current and voltage, and the mathematical expression of the electric energy metering mechanisms is as follows:
in the formula: p ∑ Three-phase total power (electrical energy is the integral of power, i.e., the accumulation of electrical power);
P W1 ，P W2 ，P W3 power measurement results of three power measurement mechanisms are obtained;
u A ，u B ，u C phase voltage, i.e. the voltage of each phase line to the phase line (ground);
i A ，i B ，i C is the current for each phase.
The metering result of the three-phase four-wire system electric energy meter is accurate, but the ground wire (neutral wire) of the power grid needs to be introduced, so the measuring structure is more complex.
A schematic diagram of an electric energy meter in a three-phase three-wire system grid is shown in fig. 2. Obviously, only two electric energy metering mechanisms W are needed for metering three-phase electric energy at the moment 1 ，W 2 Except that W is 1 ，W 2 The voltage branches are respectively bridged between A-B, C-B, so that the structure and the wiring of the three-phase electric energy meter are greatly simplified, the three-phase four-wire electric energy meter is an important simplification, and the basic condition is three-phase load symmetry, namely:
i A +i B +i C ＝0 (2)
then there is
i B ＝-i A -i C (3)
Thus, the formula (1) can be simplified into
Therefore, the three-phase three-wire electric energy meter is widely applied.
The problem is that the condition of equation (2) is not satisfied under normal conditions, and the three-phase load has a deviation Δ i under substantially the same conditions, that is: i.e. i A +i B +i C ＝Δi (5)
Thus, the correct expression of the formula (4) is
(6) The last term in the formula is the error of the measurement result of the three-phase three-wire electric energy meter. The three-phase three-wire system electric energy meter only needs to introduce three live wires, has a simple structure, and has a principle error when the three-phase load is unbalanced.
Moreover, the existing three-phase electric energy meter cannot be directly used for high voltage, the high voltage is converted into low voltage (100V) through a voltage transformer (PT), and the large current is converted into small current (5A or 1A) through a Current Transformer (CT), so that the complexity and the manufacturing cost of the structure are improved, and meanwhile, the integral metering calibration and verification cannot be realized.
SUMMERY OF THE UTILITY MODEL
The utility model overcomes above-mentioned shortcoming provides a measurement is accurate, can be used for high-voltage line measuring three-phase electric energy meter.
The utility model provides a technical scheme that its technical problem adopted is: a three-phase electric energy meter comprises
The current detection unit is used for detecting the line current of the line;
the voltage detection unit is used for detecting line voltages which are arranged at intervals in pairs;
and the electric energy measuring and calculating unit is used for receiving the detection results of the current detection unit and the voltage detection unit and calculating the accumulated electric energy.
The voltage detection unit can be a voltage/voltage converter connected between two phases in a bridging manner, and outputs a detected line voltage signal to the electric energy measuring and calculating unit.
The voltage detection unit can comprise a voltage divider and a current/voltage converter which are connected in series across two phases, and outputs the detected current signal in the series circuit to the electric energy measuring and calculating unit.
The voltage divider may be formed by a plurality of series-connected voltage-dividing resistors.
The voltage dividing resistor is surrounded by a plurality of conducting rings connected by capacitors.
The output end of the conducting ring can be connected with a power supply unit, and the current output by the conducting ring is converted into direct current power supply to be output.
The current detection unit may include a current/voltage converter connected in series in the line, and converts the detected line current into a voltage signal, which is output to the power measurement and calculation unit.
The power measuring and calculating unit can comprise
The A/D conversion module converts the detection results of the current detection unit and the voltage detection unit into analog/digital signals and converts the analog/digital signals into A/D level signals;
the power calculation module calculates a power value according to the A/D level signal;
a digital/frequency conversion module for converting the calculated power value into a pulse of a corresponding frequency;
and the electric energy accumulation module accumulates the pulse signals to obtain an electric energy value.
The utility model discloses a current detection unit, voltage detection unit detect respectively and obtain accurate proportion in the line current and the line voltage signal of each looks, convey in unison again in the unit is calculated to the electric energy, calculate the unit by the electric energy and carry out electric energy accumulation calculation, under the prerequisite that does not improve the hardware cost, eliminate the principle error that arouses by three-phase load current imbalance, the accuracy of calculating the result has greatly been improved, furthermore, adopt the mode that detects the electric current that acts on the voltage divider, realize the measurement to line voltage, can need not to use voltage transformer, make electric energy meter itself not only have lower complexity, still further improve the degree of accuracy that high-tension line electric energy was calculated, can obtain better application in high-tension electricity network's electric energy detection.
Drawings
FIG. 1 is a schematic structural diagram of a three-phase four-wire electric energy meter in the prior art;
FIG. 2 is a schematic structural diagram of a three-phase three-wire system electric energy meter in the prior art;
fig. 3 is a schematic structural diagram of a first embodiment of the present invention;
fig. 4 is a schematic structural diagram of a second embodiment of the present invention.
Detailed Description
As shown in fig. 3, which is a schematic structural diagram of a preferred embodiment of the present invention, the present embodiment is a novel three-phase three-wire electric energy meter suitable for line voltages of 380V, 10kV and 35kV, and phase currents of 0-1000A, and the line currents i in the three phases A 、i B 、i C The measurement is realized through current/voltage converters (hereinafter referred to as I/V converters) I/V (1), I/V (2) and I/V (3) which are connected in series in the respective lines, detected current signals are converted into voltage signals, and the voltage signals are output to the electric energy measuring and calculating unit. And three line voltages u AB 、u BC 、u CA The detected voltage signals are also output to the electric energy measuring and calculating unit through voltage/voltage converters (V/V converters) V/V (4), V/V (5) and V/V (6) which are connected between every two phases. The three-way line voltage signal and the three-way line current signal act on the input end of an electric energy measuring and calculating unit M (7) at the same time, the electric energy measuring and calculating unit converts the received analog signals measured by I/V (1), I/V (2), I/V (3), V/V (4), V/V (5) and V/V (6) into A/D level signals through A/D conversion, and the mathematical expressions of the three-phase three-wire electric energy meter with the common C phase and the common A phase are respectively as follows according to the mathematical expression of the three-phase three-wire electric energy meter with the common B phase described in the formula (6):
if the average value of the formulas (6), (7) and (8) is taken, the total power of the three phases is:
(10) The last term in the formula is an error term of the measurement result, and the symmetry of the three-phase voltage is considered, namely:
u A +u B +u C ＝Δu (11)
(10) The error term in the equation becomes:
it is apparent that Δ P is greatly reduced from the error in the expression (6), and is usually negligible.
The total power P thus obtained by the above-mentioned measurement and calculation ∑ The digital/frequency conversion module (hereinafter referred to as D/F conversion) converts the calculated power into pulses of corresponding frequencies; and finally, accumulating the pulse signals to obtain an electric energy value. The measuring, calculating, D/F converting and accumulating processes can be obtained by software calculation in a computer and a chip, wherein u AB ＝-u BA ， u BC ＝-u CB ，u AC ＝-u CA 。
It can be seen from this embodiment that the utility model provides a three-phase electric energy meter, its hardware cost does not have too big difference with current three-phase four-wire electric energy meter, but it has realized the three-phase three-wire electric energy meter of no principle error, and from the outside, its line connection is also simple with current three-phase three-wire electric energy meter equally, therefore promotes and uses fairly easily.
The utility model discloses a another embodiment provides a three-wire high-voltage electric energy meter of net gape three-phase, is the schematic structure of this embodiment as shown in fig. 4.
In order to ensure safety, three-phase high-voltage electric energy meters with network portsMeasuring mechanism W 1 ，W 2 ，W 3The structures are completely the same, so that only the phase A of W is used 1 This is illustrated for example purposes. W 1 Is positioned at the A-phase port of the power grid, the electric energy transmission direction is from A → A' (the electric energy is a negative value when the phase is reversed), and the A-phase line current i A Measured by I/V converter I/V (1), the ratio of I to A The voltage signal of the power measuring and calculating unit M (4) is output to an input channel of the power measuring and calculating unit M (4); a voltage divider R is connected between two phases A, B in series A And an I/V converter I/V (3), R A The current flowing through I/V (3) is proportional to U AB Thus through the detected and voltage divider R A The current in the series circuit is converted into a voltage signal and is output to the electric energy measuring and calculating unit M (4); similarly, the line voltage between two phases A, C is measured by measuring R C The current flowing through I/V (2) is proportional to U AC Also to the power measuring unit M (4). The voltage divider is composed of a plurality of series-connected voltage dividing resistors so as to ensure absolute safety of voltage and power consumption of each voltage dividing resistor. The divider resistor is externally wound with a plurality of conducting rings connected by capacitors to form another capacitor voltage dividing branch at intervals, so as to form a squirrel-cage-shaped equipotential shielding mechanism, thereby ensuring the accuracy and the anti-interference of the voltage division of the resistors. Capacitance voltage-dividing branch C formed by conducting rings A 、C C Current (typically 2 mA) through S P (5) Collected and processed, and converted into DC power output of W 1 The internal current provides a dc supply.
The hardware structure of the electric energy measuring and calculating unit M (4) is basically the same as that of a three-phase three-wire electric energy meter chip, and the following calculation is carried out
The same principle is that:
adding the measurement results of the three measurement mechanisms and dividing the result by 3 to obtain the product
This is the result of the three-phase power measurement of the formula (10) in the first embodiment, which is different from the sequence of the formulas (6) to (10), but the resultant result is the same.
In this example, W 1 ，W 2 ，W 3 Three measurement mechanisms respectively select three ports A, B and C as electric reference points, and W is used 1 ，W 2 ，W 3 Are all arranged in an electric and thermal shielding mechanism to ensure the safety and stability of the current level. Since this embodiment is applied to the measurement of high-voltage electrical energy, the results of the line voltage and the line current measured by the power measuring and calculating unit M (4) in each measuring mechanism need to be sent to the ground through the carrier chip T (6), received by the ground carrier system, and then sent to another power measuring and calculating unit for further data processing, and the results sent by the power measuring and calculating unit M (4) through the carrier chip T (6) can include current, voltage, and protection signals, etc. without being limited to electrical energy. Therefore, the embodiment can be better applied to the electric energy measurement in a high-voltage line, such as an electric energy metering cabinet for high distribution voltage (10kV, 35kV) or a three-phase three-wire electric energy meter for manufacturing high grid voltage (110kV, 220kV and above).
In addition, the current/voltage converter can be realized by replacing a current transformer CT and resistance sampling, and the voltage/voltage converter can be realized by replacing a voltage transformer PT.
The three-phase electric energy meter provided by the utility model is introduced in detail, and the principle and the implementation mode of the utility model are explained by applying a specific example, and the explanation of the above example is only used for helping to understand the method and the core idea of the utility model; meanwhile, for the person skilled in the art, according to the idea of the present invention, there may be changes in the specific implementation and application scope, and in summary, the content of the present specification should not be understood as a limitation to the present invention.
Claims (8)
1. A three-phase electric energy meter is characterized in that: comprises that
The current detection unit is used for detecting the line current of the line;
the voltage detection unit is used for detecting line voltages which are arranged at intervals;
and the electric energy measuring and calculating unit is used for receiving the detection results of the current detection units and the voltage detection units and calculating the accumulated electric energy.
2. A three-phase electric energy meter according to claim 1, characterized in that: the voltage detection unit is a voltage/voltage converter which is bridged between two phases and outputs a detected line voltage signal to the electric energy measuring and calculating unit.
3. The three-phase electric energy meter according to claim 1, characterized in that: the voltage detection unit comprises a voltage divider and a current/voltage converter which are connected in series and are connected across two phases, and the detected current signal in the series circuit is output to the electric energy measuring and calculating unit.
4. A three-phase electric energy meter according to claim 3, characterized in that: the voltage divider is composed of a plurality of series-connected voltage dividing resistors.
5. The three-phase electric energy meter according to claim 4, characterized in that: and a plurality of conducting rings connected by capacitors are wound outside the voltage division resistor.
6. The three-phase electric energy meter according to claim 5, characterized in that: the output end of the conducting ring is connected with a power supply unit, and the current output by the conducting ring is converted into a direct current power supply to be output.
7. A three-phase electric energy meter according to any one of claims 1 to 6, characterized in that: the current detection unit comprises a current/voltage converter connected in series in the line, converts the detected line current into an A/D level signal and outputs the A/D level signal to the electric energy measuring and calculating unit.
8. A three-phase electric energy meter according to any one of claims 1 to 6, characterized in that: the electric energy measuring and calculating unit comprises
The A/D conversion module converts the detection results of the current detection unit and the voltage detection unit into analog/digital signals and converts the analog/digital signals into A/D level signals;
the power calculation module calculates a power value according to the A/D level signal;
a digital/frequency conversion module for converting the calculated power value into a pulse of a corresponding frequency;
and the electric energy accumulation module accumulates the pulse signals to obtain an electric energy value.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CNU2007200030110U CN201011520Y (en) | 2007-01-29 | 2007-01-29 | Three-phase electric energy meter |
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| CNU2007200030110U CN201011520Y (en) | 2007-01-29 | 2007-01-29 | Three-phase electric energy meter |
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Cited By (3)
| 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 |
| CN112180157A (en) * | 2020-09-28 | 2021-01-05 | 国电联合动力技术有限公司 | Wind turbine generator generating capacity metering method and intelligent analysis method and system based on wind turbine generator generating capacity metering method |
-
2007
- 2007-01-29 CN CNU2007200030110U patent/CN201011520Y/en not_active Expired - Fee Related
Cited By (7)
| 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 |
| CN112180157A (en) * | 2020-09-28 | 2021-01-05 | 国电联合动力技术有限公司 | Wind turbine generator generating capacity metering method and intelligent analysis method and system based on wind turbine generator generating capacity metering method |
| CN112180157B (en) * | 2020-09-28 | 2022-07-29 | 国电联合动力技术有限公司 | Wind turbine generator generating capacity metering method and intelligent analysis method and system based on wind turbine generator generating capacity metering method |
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| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20080123 Termination date: 20100129 |