Since 2003, after the large-scale transformation and construction of China's urban and rural power grids, the demand for three-phase multi-function meters in the power system has grown rapidly. The 2004 production is estimated to be about 700,000 units, which is less than the total output of the national electricity meter. With a 1% share, 11% of the total output value of the watt-hour meter was created. As a result, international and domestic electric meter companies have been optimistic about business opportunities, seized the development of new technologies, and continuously introduced new products for three-phase multi-function meters to meet the application needs of the electric energy meter market.
Compared with traditional mechanical watches, the three-phase multi-function meter adopting the principle of electronic measurement has the advantages of high precision, multi-parameter measurement, and harmonic power electric energy metering. From the overall evaluation, the three-phase multi-function meter is also a steady-state power load metering product. Due to the expansion of its application field, the power system constantly puts forward new technical requirements for the meter. The existing three-phase multi-function meter performance and quality cannot fully meet the needs of the power system. Therefore, how to correctly grasp the development trend of product technology, improve product design, and push the technical level of the three-phase multi-function meter to a new height is undoubtedly a common concern of the meter industry and the power system.
First, the introduction of new three-phase multi-function energy meter technology introduced three-phase multi-function meter new technology, representing the current international energy meter technology the highest level:
1. High-precision, long-life measurement The active energy metering with an accuracy of 0.1% exceeds the maximum accuracy requirement of IEC online metering. The error curve has a bandwidth of +/-0.05%.
0.2S class three-phase fundamental wave meter with phase-divided 2-50th harmonic active power metering;
0.2S class long-lived electrical gateway meter with power quality metering module.
2, high-speed, real-time measurement of AC sampling rate of 256 points / cycle, the shortest recording period of 10 milliseconds;
Power quality measurement: Transients of 63 harmonics, voltage flicker, fault recording, 78 microseconds, and 99.9999999% of power supply reliability.
3, open, high-speed communication technology application open communication protocol IEC62056-61/62/53/46/42, meter reading, rate, load control data exchange;
Internet communication, automatic sending of E-mail alarm signal, system operation status refresh, data recording, connection to some international well-known electricity billing system gateway table via Ethernet, Web server can directly read various actual data and power of the meter Quality parameters, without any special software.
4. Three-phase energy measurement special chip adopts low-frequency filtering method to measure harmonic reactive power three-phase measurement chip, high âˆ‘-â–³A/D, load dynamic range 1000:1, linearity 0.1%, with temperature measurement function, on-chip The interface can be directly connected to the differential current transformer;
3-phase SOC single chip with better than 0.1% accuracy, 21-bit second-order âˆ‘-Î”A/D, 32-bit programmable electric energy calculation engine, dynamic range of load 2000:1, on-chip integration: high-speed 8051 single-chip microcomputer, hard real-time clock , LCD drive circuit, watchdog circuit, timer, a variety of memory, a variety of communication interfaces.
5, harmonic power energy measurement standards in Europe: three-phase 0.01-level standard table, with harmonic power measurement function; established harmonic active power, harmonics apparent power measurement transmission standards;
In the United States: automatic energy meter calibration system, in the arbitrary waveform harmonic content less than 30%, the measurement accuracy of +/-0.005%-0.05%; high-precision three-phase standard table, in the power factor is less than 0.5 (60 degrees - 90Â°), measurement accuracy is +/-0.02%/power factor; electrical power standard source, provides seven kinds of non-sinusoidal signal reactive power calculation method.
It should be pointed out that although the application of new technologies in the IT industry has promoted the rapid development of imported energy meter technology, the imported online energy meter technology is now not standardized, with 0.1-level energy meter, arbitrary waveform power and energy metering, and 0-360Â° metering. Other issues of concern are being explored. The error stability and reliability indicators of the energy meter have not been quantified. Device damage, data loss, and self-inspection errors have occurred from time to time. These conditions indicate that there is a long way to go before the technology of imported energy meters matures. process.
Second, the domestic three-phase multi-function energy meter new technology domestic electronic three-phase multi-function meter technology development started late, in recent years, focusing on the absorption of international measurement technology and management experience, strengthen self-development, has made many new technical achievements:
1. Three-phase multi-function meter 0.2S class active power metering, 16-bit âˆ‘-â–³A/D, 160MIPS DSP, AC sampling rate 256 points/cycle, running and standby two sets of time period, load curve recording and capacity 4M bytes of memory, wide range of supply voltage, mutual inductor synthesis error compensation, transformer copper loss, core loss calculation;
0.5S three-phase fundamental wave active meter;
The three-phase SOC single-chip or three-phase active and reactive metering chip low-end three-phase multi-function meter design, technically adapt to the large-scale, wide-ranging market demand;
High-voltage energy meter, using electronic sensors, suspended power supply design, active energy metering accuracy is 0.5, for 10 kV medium voltage directly metering electric energy.
2. Harmonic power, energy metering three-phase harmonic meter, active power metering 0.2S class, reactive power metering 0.5S class, high accuracy fundamental and harmonic active energy metering, real-time integration method to calculate the total active energy , through the FFT algorithm to provide fundamental, harmonic electrical energy and harmonic power direction;
Impact load electrical energy measurement theory and algorithm, applying generalized power theory, defining the power of single-phase circuit and three-phase circuit of arbitrary waveform, applying sine-wave circuit power theory, traditional non-sinusoidal circuit power theory and generalized power theory to perform active and no impact load Work, apparent, distortion, calculation of three-phase asymmetric power energy;
Based on the measurement of harmonic reactive power based on the IIR Hilbert digital filter method, the Hilbert digital filter has excellent frequency response characteristics. The numerical calculation is simple. The calculated harmonic reactive power is only 0.02% worse than the simulation experiment result.
Harmonic active power flow analysis method, the research pointed out: FFT theory has limitations, the actual power load, in addition to the fundamental wave and integral frequency multiplication, there are interharmonics exist, the need to develop a new algorithm for the power meter.
3, three-phase energy metering dedicated chip with basic / harmonic energy metering three-phase multi-function measurement chip, 16-bit âˆ‘-â–³ A / D, 24-bit DSP, load dynamic range of 1000: 1, linearity of 0.1%, measurement Bandwidth 21st harmonics, integrated temperature sensor;
Hilbert digital filter to measure harmonic reactive power three-phase metering chip;
Low power three-phase active power metering chip using digital parallel algorithm and crystal frequency reduction technology.
4. Power demand side management system and terminal based on GPRS communication network The system has the functions of remote meter reading, abnormal power information alarm, power quality detection, line loss analysis, reactive voltage management and power load control management, etc. The indicator is: the concurrent data volume is not smaller than 50,000 collection points, the one-time pick-up rate is not less than 95%, the second pick-up rate is not less than 99.5%, the telemetry qualification rate is greater than 98%, and the time-to-hour accuracy is less than 100 milliseconds.
5, the gateway table remote calibration system The system consists of multiple gateway table measurement, calibration circuit and computer communication network, is to put the high-precision three-phase standard table in the substation environment conditions meet the requirements of the place, the measured current transformation is The intermediate transformer of 0.02 class and 5/0.5A is connected to the secondary circuit of the metering current transformer. The three-phase connection mode and the active and reactive power metering methods of the standard meter and the gateway meter are switched by the IPC instruction. Real-time error is sent to the system master via a dedicated channel, and the overall system error is 0.1%.
6. Digital three-phase standard meter with accuracy of 0.02% for power quality and energy metering standards, four-quadrant measurement, multiple reactive power metering methods, harmonic and fundamental power measurement, 50 harmonic analysis, three-phase Asymmetry measurement
The sinusoidal reactive power measurement standard of the power system, which is based on the current comparator technology, is traced back to the basic electrical parameters, and the expanded uncertainty of the sinusoidal reactive power measurement is 75Ã—10-6;
Power quality measurement standards for power systems, including: Harmonic voltage, current measurement, Harmonic times from DC and 2-100 times integer harmonics, any interharmonics, harmonic voltage expansion uncertainty of 0.02%, harmonic Wave current expansion uncertainty is 0.04%; flicker, commonly used indicators are short-time flicker Pst (10min) and long-term flicker Plt (2h), the standard device's extended uncertainty of 0.5%; frequency: 1Hz -21 MHz, the device has an extended uncertainty of 2Ã—10-10; phase, and the standard device has an extended uncertainty of 0.02Â°;
In terms of product specifications, given that there is no unified standard for three-phase multi-function meters in the world, the China Electrotechnical Instrumentation Standardization Technical Committee has organized the drafting of the national standard â€œSpecial Requirements for Multifunctional Energy Metersâ€ and is now entering the validation stage. The purpose of this standard is to provide manufacturers and users of electrical energy with a product specification and to reflect most of the contents of the product order specification. The general requirements for a multi-purpose meter will refer to the contents of relevant national standards in China. .
To sum up, after more than ten years of development, China's three-phase multi-function meter types are relatively complete, and the development level of medium- and low-end meter technology is relatively high, especially the impact load energy meter theory and algorithm, harmonic reactive power metering The three-phase special chip with harmonic power measurement, high-voltage energy meter, application of GPRS communication technology, and remote calibration of electric energy are of innovative significance. However, it should also be noted that the high-end meter technology has not been fully passed, and the measurement of electricity gateways is still dominated by imported meter. This is a question worth pondering.
Third, the future of three-phase multi-function energy meter technology to face the status quo, looking to the future, the need to advance forecast the application of electric meters and technical requirements of continuous changes in order to correctly grasp the direction of future product technology.
1. Development of application areas: In recent years, China's social power consumption has grown rapidly, with nationwide networking, construction of UHV power grids, grid connection of millions of kilowatts of generators, home networking, improvement of grid operation and management, and new measurement technologies. Application and other elements to promote the expansion of meter application are mainly:
From electricity metering and billing to measurement of distribution transformers, substations' economic management and demand side management;
From user billing to billing for power generation at the power plant and electricity exchange between provincial power grids;
The billing of large industrial users from 315 kVA and above extends to the billing of commercial, non-industrial, and general industrial households with 100 kVA and above. The expansion of the above meter application area has caused the total amount of metering points to be estimated at 600,000. Expanded to 4 million, the demand for meter applications is promising.
2. Update of technical requirements: With the expansion of the application scope of electricity meters, the power system proposes many common requirements for metering that require traditional billing meters, active and reactive energy metering, maximum demand measurement, rate periods, and single direction. , bidirectional and incomplete four-quadrant measurement, multi-parameter measurement, multiple timing requirements, multiple communication methods, self-test, alarm, power meter reading, voltage loss, phase failure, power failure, loss of flow, three-phase asymmetry, Programming events, demand resets, etc.
Newly proposed general requirements, operating and standby two sets of time periods, 0-360Â° metering, time-stamped apparent energy metering, minimum demand metering, Qh metering, automatic temperature error compensation, harmonic voltage, total current content and Harmonic pollution degree measurement, anti-theft basic technology, at the same time, billing meter to be accurate and reliable, simple and practical;
The special requirements of the customs table, the highest accuracy to 0.1, the meter stability and reliability indicators to be quantified, low load measurement, demand cycle, time period synchronization and main and vice table real-time comparison, remote meter calibration ;
The special requirements for measurement of large industrial households include harmonics, impact load measurement, power over limit alarm, main transformer loss measurement, transformer error compensation, power quality measurement, etc.
Special requirements for medium capacity metering, high current measurement, half-wave measurement by current transformers, three-phase unbalanced, asymmetrical metering;
Substation special requirements for incoming and outgoing metering, main transformer loss measurement, substation active, reactive, and apparent energy balance measurement, reactive power control signal output, special requirements for subscriber lines, and reference to the special requirements for measurement of large industrial households ;
Particular requirements for measurement of distribution transformers, power outage acquisition, three-phase unbalanced, asymmetrical measurements, neutral current measurement, transformer oil temperature measurement, transformer loss measurement and active, reactive, apparent power balance, power line loss Verification, etc.
The special requirements of the power demand side management system terminal, power over-limit alarm and active reporting, power load switch switching signal output, etc.
At the same time, in order to rectify and suppress the current requirement for the three-phase multi-function meter with too many functions and the technical conditions are out of order, it is recommended that the power system formulate uniform technical specifications according to different application fields.
Note: The degree of harmonic pollution is tentatively defined as: non-fundamental apparent power/fundamental apparent power 3, development trend of product technology Three-phase multi-function meter technology to track the continuous change in application requirements, also expresses future products The development trend of technology:
Multi-meters: Development of a single billing product to gateway metering, distribution transformer metering, substation metering, large industrial metering, medium capacity metering, electricity demand side management systems and terminal 6 products ;
In order to develop high-precision, high-stability, high-reliability, rapid measurement, 0-360Â° measurement, multi-communication methods and protocols, the gateway power meter has been compared with similar domestic and international electric meters to provide quantitative indicators and test methods.
Cost-effective three-phase multi-function meter requires accurate, simple and reliable measurement, practical and practical, and gradually develops three-phase SOC single chip, develops measurement technology with harmonic voltage, current total content and harmonic pollution degree, and studies temperature, voltage and frequency. Adaptive measurement of phase change;
Harmonic active, reactive, and apparent power metering utility products, improving power factor calculation methods under harmonics, advancing the establishment and development of the power quality market, and also preparing for improving the measurement accuracy of smelting enterprises and electrified railways;
The early three-phase multi-function meters need to be replaced by new generations, and a new generation of technical specifications for electric meters should be proposed through investigation and research.
Based on the power demand side management system and terminal of the GPRS communication network, it is necessary to improve the real-time and security technologies. In the long run, even if the power is not tight in the future, it is used for metering and meter reading of distribution transformers and remote meter reading for residents' electricity use. Its development prospects are also very good;
Power network loss measurement and anti-tampering basic technologies, including: electricity with time scale, power fluctuation analysis software, power abnormal alarm and active reporting, transformer, power line loss measurement, power system node, bus and power line power balance measurement;
National networking, provincial network total electricity metering, calculation and electric energy data networking, to mention the agenda;
Strengthen the construction of domestic power quality and energy metering standards, including: the construction of fundamental wave, harmonic power metering standards, importing new international standards for metering equipment that are in urgent need of domestic imports, and meeting the requirements for online metering new product measurement;
Finally, it is to study and formulate the quality evaluation standards and test methods for three-phase multi-function meters to improve the overall technical quality of operating the meters on the power grid.
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