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Research on Model Construction of Electric Energy Metering System Based on Intelligent Sensor Data

Research on Model Construction of Electric Energy Metering System Based on Intelligent Sensor Data Hindawi Advances in Mathematical Physics Volume 2023, Article ID 1296165, 8 pages https://doi.org/10.1155/2023/1296165 Research Article Research on Model Construction of Electric Energy Metering System Based on Intelligent Sensor Data 1 2 2 2 2 Hang Li, Luwei Bai , Jia Yu, Yongmei Mao, and Zhenzhen Hui Inner Mongolia Power (Group) Co., Ltd., Inner Mongolia Power Research Institute Branch, Hohhot, 010020 Inner Mongolia, China Electric Energy Measurement Supervision Center, Inner Mongolia Power (Group) Co., Ltd., Inner Mongolia Power Research Institute Branch, Hohhot, 010020 Inner Mongolia, China Correspondence should be addressed to Luwei Bai; b20160901216@stu.ccsu.edu.cn Received 23 September 2022; Revised 31 October 2022; Accepted 20 March 2023; Published 3 May 2023 Academic Editor: S. E. Najafi Copyright © 2023 Hang Li et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The informatization construction of the power grid is becoming increasingly popular, business application systems are constantly emerging, and power-related data is rapidly expanding. These discrete power data are scattered in various application systems, and it is not easy to directly provide advanced enterprise applications. The establishment of intelligent power statistical model is an urgent need for constructing power grid informatization. This paper proposes a model of an electric energy metering system based on intelligent sensor data and introduces the existing digital metering system. This model is the integration and promotion of business integration based on the digital metering system. It is the first time to apply new metering equipment, such as measurement and control devices with integrated metering functions, and new metering technologies, such as IEC 61850 electricity meter reading applications. It is hoped that this paper can lay a foundation for further research. 1. Introduction matically generates a report. The actual load verification function can verify the inspected digital electric energy Science and technology have developed rapidly, and the meter at the substation site without affecting the use of the intelligence and informatization are becoming increasingly inspected digital electric energy meter. Various problems, popular in the industrial field. The digital energy meter cal- such as power imbalance, seriously hinder the engineering ibrator can accept the output signal of the standard power, application process of digital metering technology. Accord- and, after AD conversion, use the internal digital energy ing to relevant data statistics, in 2020, among the 10 kV lines meter to calculate the electric energy and output the electric of Wuhan Power Supply Company, the ratio of users with a energy pulse to the higher precision electric energy metering line loss rate of more than 5% was 12.6%, the percentage of equipment to carry out the calibration to achieve the quan- users with a line loss rate of more than 10% was 7.1%, and tity value transmission. Although the accuracy of digital the percentage of users with a line loss rate of more than metering equipment has been significantly improved, there 8% covered by unique transformer customers was 5.3%. are still many problems in actual operation, such as frequent During 2018-2021, more than 20000 defaulters and power communication failures and abnormally large measurement thieves were found, saving more than 80 million yuan of errors under the condition of good equipment performance, economic losses. Currently, the annual loss due to electric resulting in the inability to upload measurements and inac- energy theft in China is up to 20 billion yuan, and the value curate upload data [1, 2]. The virtual load verification func- is increasing yearly. Taking the yearly electricity sales of 70 tion controls the output of the standard power source by billion kWh in a province as an example, if the line loss editing the verification scheme of the electric energy meter, caused by artificial electricity theft increases by one percent- verifies the digital electric energy meter in detail, and auto- age point, the power loss will be up to more than 700 million 2 Advances in Mathematical Physics kWh, equivalent to nearly 400 million yuan [3]. Inductive In traditional substations, the energy metering system con- equipment must absorb active and reactive power from the sists of transformers and electronic energy meters. The trans- power system during operation. Therefore, after installing formers convert high voltage/large current into small voltage/ shunt capacitor reactive power compensation equipment in current signals of 100/57.7 V or 1/5A and then input them to the power grid, it will be able to provide reactive power con- the electronic energy meter [6]. The structure of an electronic sumed by compensating inductive load, reducing the reac- watt-hour meter is similar to that of an induction watt-hour tive power supplied by the power grid side inductive load meter, composed of two parts: a measuring mechanism and and transmitted by the line. To effectively grasp the existing auxiliary components. The measuring instrument is mainly issues in the actual operation of the digital electric energy written as an electronic circuit. Its measuring elements are metering system and to clarify the aspects and contents of composed of a UI multiplier, U/f converter, and counter. The the practical work of digital metering in the next step, the auxiliary components are the same as those of the inductive State Grid Jiangsu Electric Power Company selected Wuxi watt-hour meter. To complete the accumulation of electrical as the research object to investigate the operation of all dig- energy. In the intelligent substation, the electric energy meter- ital electric energy meters under the jurisdiction of its urban ing system has two forms: the firstistouse electronic trans- area. Statistics were carried out, a field investigation was formers, digital input merging units, and digital electric energy meters. The electronic transformers directly output dig- conducted on the application status of the digital electric energy metering system in Xijing intelligent substation, ital quantities, and the subsequent data transmissions all use and valuable first-hand information was obtained [4]. optical fibers. The second is to use traditional electromagnetic The main work done in the paper can be described as transformers still. The analog input merging unit digitizes the follows: (1) introduces the statistics of operating faults of voltage and current signals output by the conventional trans- Wuxi digital electric energy meters and analyzes the possible formers on the spot. This measurement system structure is causes of various spots; (2) taking the digital power measure- adopted because the technology of electronic transformers is ment on the high-voltage side of the main transformer in immature [7]. The configuration principle of the electric energy Xijing No.1 substation as an example, combined with digital metering device includes that the secondary circuit of the volt- measurement; the basic structure of the system points out its age transformer in the electric energy metering device for trade shortcomings in practical applications; (3) this paper sum- settlement above 35 kV shall not be equipped with the auxiliary marizes the current practical problems faced by the power contact of disconnector. The electric energy metering device for metering system based on intelligent sensor data in engi- trade settlement is installed at the user’s place, and the user sup- neering applications and proposes corresponding solutions plying power at 10 kV and below should be equipped with a to provide a reference for the next step in the development national unified standard electric energy metering cabinet or of intelligent power systems. electric energy metering box. To improve the accuracy of low load metering, electric energy meters with the overload of 4 times or more shall be selected. Figure 1 shows the structural 2. Theoretical Analysis on Electric comparison of these three metering systems. Energy Metering W = U × I × t, ð1Þ Electric energy measurement has two main functions: on the one hand, it is used for internal assessment and settlement of or power grid enterprises, and on the other hand, it is used as the basis for trade settlement between power generation, W = P × t, power supply, and electricity consumption [5]. To ensure ð2Þ that the electric energy metering device can accurately mea- W = W + W + W +⋯W : n 1 2 3 n sure the electric energy, first of all, the category of electric energy metering device should be correctly selected. Sec- In the above formula, W represents electric energy, U rep- ondly, choose the electric energy meter and instrument resents the actual voltage value, I represents the actual current transformer with excellent performance and quality, as well value, P stands for electrical power, and t represents the elec- as the secondary circuit wire section, and install and main- tricity consumption time. tain them as required to ensure the safe, accurate, and reli- able operation of the electric energy metering device. 3. Research and Analysis Electric energy measurement accuracy directly affects the internal assessment and analysis results of power grid com- 3.1. Statistical Analysis on Operation of Wuxi Digital Electric panies or the fairness of trade settlements. Therefore, the Energy Meter. Wuxi, Jiangsu, has several smart substations. electric energy measurement system must be accurate and The city with the most extensive range of digital power reliable. The role of electric energy measurement standards metering systems in Jiangsu Province is Wuxi Power Supply in energy conservation and consumption reduction includes Company. The technical advantages of intelligent substa- that scientific and advanced electric energy measurement tions include the following: the smart substation can achieve tools provide accurate data for energy-saving transforma- an excellent low-carbon environmental protection effect, tion, and the analysis of electric energy measurement data and the intelligent substation has good interaction and reli- provides the scientific basis for energy-saving change. ability characteristics. Advances in Mathematical Physics 3 Electronic energy meter Traditional current Traditional voltage transformer Cable Optical fiber Digital energy meter Electronic current Electronic voltage Optical fiber transformer Optical fiber Digital energy meter Figure 1: Structure comparison of three metering systems. Table 1: Statistics by voltage level. Up to now, the total number of digital meters under the jurisdiction of Wuxi city is 251, involving 43 substations of 3 Voltage Total number Number of Failure voltage levels. Among them are three 500 kV substations level (kV) of digital tables failure tables rate (%) involving 32 photoelectric meters, 17 220 kV substations 500 32 1 3.1 involving 91 photoelectric meters, and 23 110 kV substations 220 91 5 5.5 involving 128 photoelectric meters. The intelligent substa- 110 128 39 30.5 tion uses reliable, economic, integrated, low-carbon, and environment-friendly equipment and design, which can support the real-time online analysis and control decision- Table 2: Statistics by fault type. making of the power grid, with the basic requirements of the whole station information digitization, communication Number of Percentage of Fault type fault tables failure table (%) platform networking, information sharing standardization, system function integration, structural design compactness, Battery cannot be uploaded 21 46.7 high-voltage equipment intelligence, and operation status Battery error 9 20.0 visualization. Other faults 15 33.3 This paper mainly conducts statistics on the operation of digital meters in operation under the jurisdiction of the Table 3: Statistics by manufacturer. Wuxi urban area. The failure rate of digital electric energy meters is generally 16%, which is higher than the failure rate The number of of traditional electronic energy meters. To further analyze digital meters Number of Percentage of Manufacturer the operation of the digital electric energy meter, Table 1 is supplied by the fault tables failure table (%) by voltage level, Table 2 is by fault type, and Table 3 is the manufacturer classification statistics of manufacturers. 1 90 2 2.2 From the above data, we can preliminarily summarize 2 74 19 25.7 the following conclusions (Figure 2). It can be seen from 3 36 2 0.56 Table 1 that as the voltage level decreases, the failure rate 4 17 2 11.8 gets higher and higher. Many faults include failure to upload power and power error. The primary responsibility is that 5 9 7 77.8 the administration cannot be uploaded due to communica- 6 5 3 60.0 tion failure; different manufacturers’ digital electric energy meters significantly differ in failure rate. The communica- tion failures of digital watt-hour meters mainly include were further analyzed. A communication failure causes the frame loss, communication delay, and channel abnormality inability to upload the electricity. The judgment is based (Figure 3). on the standard measurement of the electric energy meter, Through exchanges and discussions with relevant tech- but the centralized meter reading center cannot read the nical personnel of the operation and maintenance unit and electric energy. The power error should be the wrong config- on-site inspection, the possible causes of various failures uration of the parameters of the electric energy meter. The Analog input type merging unit Digital input type merging unit 4 Advances in Mathematical Physics The number of digital meters supplied by the manufacturer ple [9]. The idea of single server sharing is to use one PC as the server to provide network-sharing services to other PCs. There are mainly two schemes to realize this method: (1) proxy server scheme and (2) URL conversion scheme. Since Xijing Substation was put into operation, there have been relatively few problems in the digital metering system, but there are still faults, and on-site fault investiga- tion is required. Taking the digital power metering of the high-voltage side of the main transformer of Xijing Substation No. 1 as an example, the schematic diagram of the system structure is shown in Figure 4. 1 4 As shown in Figure 4, the digital energy metering sys- 2 5 tem is very different from the traditional system in struc- 3 6 ture, mainly because the energy meter is no longer directly connected to the transformer, and there are more Figure 2: The digital meter number supplied by the manufacturer. remote modules, photoelectric units, and merging units in Percentage of failure table (%) the middle. The design principles of the electric energy metering system include that the electric energy metering 77.8 system should be designed as an independent and complete 60 system. Electric energy acquisition has low requirements for real time but high requirements for simultaneity, increased requirements for electric energy acquisition accuracy, the 25.7 principle of uniqueness of data source, and the high reliabil- ity of software. The transmission signal has also become a 11.8 digital quantity, switches, and other equipment. From the 2.2 0.56 perspective of on-site operation and maintenance of meter- 1 23 4 5 6 ing, although the wiring is less, the remote modules, voltage-combining units, current-combining units, switches, Figure 3: Percentage of failure table. and other equipment are widely distributed and partially overlap with the automation system in the substation. The basis for the judgment is that the current protection and metering data sources in the intelligent substation are the secondary wiring of the metering system becomes less clear, making the whole system more complex. As electric energy same. If the data source is incorrect, the protection device should respond first. Other faults mainly refer to the crash is a cumulative value, even small errors will reach an of the electric energy meter, black screen, no indicator light, incredible degree after accumulation. For both the seller etc. The cause of such failures is defective software or hard- and the user of electricity, this cumulative value is an eco- ware of the electric energy meter itself. nomic loss. Therefore, the selection principle of measure- ment accuracy should be that the greater the capacity, the 3.2. Investigation of the Fault Situation of Digital Electric higher the accuracy. It is better to use energy meters with Energy Metering in Xijing Substation. Xijing Substation is an accuracy of 0.2 level and above for large-capacity power plants and transmission lines. the first batch of pilot projects for intelligent substations of the State Grid Corporation of China. Construction started During the on-site investigation of the digital power in July 2010 and was put into operation in December of metering fault on the high-voltage side of the main substa- the same year. The station is an intelligent substation in a tion of Xijing Substation No. 1, it was difficult for traditional complete sense. The operational characteristics and respon- substation operation and maintenance personnel to locate sibilities of intelligent substations make them have good and analyze the fault. In contrast, professional technicians interactivity. It is responsible for the data statistics of power familiar with digital power metering could infer the fault grid operation, which requires it to feed back safe, reliable, point and cause. Substation operation and maintenance accurate, and detailed information to the power grid. After experiences are also difficult to verify and figure out. In addi- the intelligent substation realizes the function of information tion, because the digital power metering system and the automation system in the substation have some overlapping collection and analysis, it can not only share the data inter- nally but also interact well with more complex and advanced equipment, such as merging units and switches, the equip- systems in the network. It adopts the design of “three layers ment focal point is not clear, which makes troubleshooting and two networks.” The SV, GOOSE, and IEEE 1588 net- very difficult. The problem-solving efficiency is low, so the works share the transmission network, and the dual network coordination and cooperation of multiple departments are required to complete the work [10]. The electric energy is redundant [8]. The voltage and current measurement equipment all uses electronic transformers. The current acquisition device is the communication center of electric transformer is based on the optical principle, and the voltage energy data. On the one hand, it collects and stores the elec- transformer is based on the capacitive voltage divider princi- tric energy data output by the digital electric energy meter in Advances in Mathematical Physics 5 ECT Remote module EVT FT3 Line current Photoelectric unit merge unit ECT EVT Switch Remote Line voltage module merge unit Meter ECT EVT Automatic meter Remote reading module center Figure 4: Xijing Substation No. 1 main transformer high-voltage side digital electric energy metering. the form of serial communication. On the other hand, the relay protection and measurement and control automation collected electric energy data is transmitted to the master system. The method of the electric energy metering system station of the electric energy billing automation system is only at the functional level [11]. For example, in terms through the uplink channel. of synchronization time synchronization, some use IRIG-B code time synchronization, and some use IEEE 1588 time synchronization, while the “direct sampling and direct hop- 4. Problems Faced by Digital Energy Metering ping” protection does not depend on time synchronization. Through the research on the application of digital energy Some sampling devices do not even access the time synchro- metering in Wuxi, Jiangsu Province, and combined with nization signal, relying entirely on interpolation synchroni- zation, and the data source of the energy meter comes the actual situation of digital metering technology, the prob- lems that still exist in trade settlement are divided into three from the switch. In this extreme case, even if the errors of the various components of the power calculation system aspects; are acceptable, the overall measurement error will exceed 4.1. Normative. The meaning of normative includes the nor- the tolerance. mativeness of the metering system structure and the norma- While for the Department of Metrology, due to the lim- tiveness of metering equipment management. The intelligent itation of majors and responsibilities, most universities and electricity meter can realize accurate and real-time cost set- scientific research institutions mainly focus on the research tlement information processing, simplifying the complex of measurement accuracy and traceability technology. process of past account processing. In the power market The normative aspect of statistical structure has not been environment, dispatchers can switch energy retailers more paid enough attention to, so the design of the current digital timely and conveniently and even realize fully automatic measurement system is not unified, which affects the accuracy switching in the future. At the same time, users can also of measurement and the reliability of measurement data. obtain more accurate and timely energy consumption and (2) Management normative accounting information. There should be a unified management specification to (1) Structural normative ensure that the digital energy metering system is accurate, Electric energy metering not only requires correct func- stable, and reliable. Traditional energy metering systems, tions, especially the electric energy metering system used according to DL/T 448-2000 “Technical Management Regu- for trade settlement, but also conforms to national manda- lations for Electric Energy Metering Devices” and SD 109- tory requirements. 1983 “Inspection Regulations for Electric Energy Metering In the process of intelligent substation design, the design Devices,” strictly stipulate the classification of metering unit mainly focuses on the stability and reliability of the points, metering device configuration, procurement, 6 Advances in Mathematical Physics installation, weekly inspection, and other links, so traditional electric energy metering systems. For example, when there electric energy metering system can measure electric energy is a fault that cannot be transmitted back to the electricity, accurately, stably, and reliably. However, no mandatory or the cause of the defect cannot be determined, and the fault recommended standard documents for managing digital point cannot be located. The most common fault in the sur- energy metering systems exist. After the digital metering sys- vey is the failure to send power back. Due to the numerous tem is put into operation from the infrastructure, there is causes of such marks and the enormous scope involved, it almost no management department, and its acceptance is is challenging to locate the spot. In response to this problem, also completed by the automation professional. In addition, related testing equipment should be developed. In Jiangsu, the follow-up operation and maintenance of the digital the electric energy accumulated by the user’s intelligent energy metering system are also tricky. The data on water, meters is collected by the local collection terminal. Then, gas, and heat consumption collected by smart meters can the electric energy is read by the remote server. Therefore, be used for load analysis and prediction. The total energy the equipment that detects the power that cannot be consumption and peak demand can be estimated and pre- returned on-site should have the following functions: dicted by comprehensively analyzing the above information, (1) Simulate the local acquisition terminal to check load characteristics, time changes, etc. This information will whether the communication function of the electric provide convenience for users, energy retailers, and distri- energy meter is in good condition bution network dispatchers; promote rational power use, energy conservation, and consumption reduction; and opti- (2) Simulate the remote server to check whether the func- mize grid planning and dispatching. (1) Up to now, there is tion of the acquisition terminal is in good condition neither detection equipment nor detection basis and means for judging the failure of digital electric energy metering (3) The simulated negative control center sends a meter equipment; (2) there are no relevant technical normative reading instruction to check whether the remote documents on how to deal with the disappointment after server can be accessed commonly the occurrence of the fault; and (3) the digital power meter- 4.3. Quantitative Traceability. For a digital energy metering ing system and the substation automation system have system to be used for trade settlement, value traceability is some overlapping equipment, and it is necessary to coordi- one of the problems that must be solved. The value trace- nate multiple departments to carry out the daily operation and maintenance of the metering system. By feeding back ability research related to digital energy metering includes three aspects: the energy consumption information provided by smart meters to users, users can be encouraged to reduce energy (1) High-precision digital energy metering algorithm consumption or convert energy utilization methods. For households equipped with distributed generation equip- (2) A high-accuracy digital power source generation ment, it can also provide users with reasonable power gen- method eration and electricity use schemes to maximize the interests of users. (3) Traceability of digital quantities to analog quantities. Under the current situation of the lack mentioned above There have been many studies on the first two prob- of normative management, it is impossible for the digital lems, and there is no recognized perfect solution for electric energy metering system to operate as accurately, sta- the third bly, and reliably as the traditional electric energy metering system. In response to this problem, the design, operation 5. Electric Energy Metering System with and maintenance, marketing, and other relevant depart- Intelligent Sensor Data ments should be coordinated to formulate a multiparty rec- ognized smart substation digital energy metering system 5.1. Electric Energy Metering System Model of Intelligent design and operation and maintenance plan, including sys- Sensor Data. At present, there is no research on electric tem wiring, equipment management, and equipment inspec- energy metering system models based on intelligent sensor tion, to form technical normative documents be enforced. data at home and abroad. For the sake of realizing the meter- ing data’s standardization and ensuring the interoperability 4.2. Detection Capability. In terms of laboratory testing, sev- and interchangeability of various devices in the metering eral testing standards, including electronic transformers, system, the following extensions are made on the premise merging units, and digital energy meters, have been formu- of analyzing the research function of the model about power lated concerning traditional electric energy metering equip- metering, demand calculating, freezing, incident report, ment, and corresponding testing platforms have been time-sharing, and segmented metering which can be clearly developed or established. Although imperfect, it can guaran- shown in Figure 5. tee the stable and reliable operation of the digital electric energy metering system under reasonable operating condi- (1) The extended model logic node MMTR is used for tions. However, there are still deficiencies in an on-site forward and reverse active energy and four- inspection. It has also been mentioned that there is a lack quadrant reactive energy and demand measurement of detection equipment and related technical specification (MMTR for three-phase electric energy meters, documents for the current on-site fault detection of digital MMTN for single-phase electric energy meters). Advances in Mathematical Physics 7 Mod INC METR LLN0 Beh INS LPHD Health MTST Namplt LPL MMTR EEhealth ISI MMXU MTUV FwdWh MTOV BCR QIVarh MTOC FwdW MTUC Q3VarFn MV GGIO PhsFwdW WYE IARC PhsTotVar PhsQ4Var Figure 5: Smart energy metering model. Under different conditions, such as electricity meter- programming, the demand cycle programming, the ing MMTR1 and demand metering MMTR2, they energy meter clearing, the demand clearing, the are distinguished by Arabic numerals suffixes event clearing, the opening of the meter cover, and opening the button box (2) The original MMXU logic node is used for remote (6) Create a new MTST logical node to save and record measurement of voltage and current (MMXU for the time zone period table three-phase watt-hour meter and MMXN for single-phase watt-hour meter) (7) Take rated voltage and current, active or reactive combined status word, energetic energy pulse con- (3) Since metering has different limits for voltage loss, stant, reactive energy pulse steady, and other energy phase loss, and current loss and protection measure- meter asset information as the extended data object ment and control alarm limits, new MTUV, MTOV, of the symbolic logical node LLN0 MTUC, and MTOC are created to complete the mon- itoring and alarm functions. Different alarms of the 5.2. Characteristics of Electric Energy Metering System Based same type of event alarms are designed with other on Intelligent Sensor Data instances, respectively, such as undervoltage MTUV1 and undervoltage MTUV2; different models are dis- (1) With the design inspiration of simplifying the com- tinguished by Arabic numeral suffixes munication network in the station, we adopt a tech- (4) Using the original logic node GGIO, there is no need nical solution that combines all-digital computing to set customized alarm events such as sampling systems and computing services with other special- abnormality, watt-hour meter failure, power failure, ties. The private communication network in the and voltage reverse phase sequence measurement system station is merged into the pub- (5) Using the original IARC recording, the program- lic communication network based on IEC 61850. ming events, for example, the time zone timetable The measurement service shares data sources and 8 Advances in Mathematical Physics (4) Standardization. For the content of the digital simu- hardware resources with other majors which sim- lation module architecture, it is required to comply plifies the secondary system in the station and lays a foundation for improving the intelligence level of with the standards issued by the relevant national departments, applicable international regulations, the measurement system corresponding industry requirements, and the provi- (2) According to the measurement business needs, the sions of pertinent power organizations to ensure the measurement is subdivided into three categories: accuracy and standardization of the system simula- assessment, settlement, and measurement points tion data. Distinguish the characteristics of metering that may be converted into settlement points. Differ- devices in different cities and counties. Conduct dig- ent metering points design various implementation ital simulation modeling of electric energy metering schemes and propose other technical conditions devices based on the principle of “unified standard, unified platform, and unified implementation” (3) The IEC 61850 node and service model are estab- lished for the new generation of intelligent substa- tion metering and metering management. The IEC Data Availability 61850 file service is used to realize the real-time recording of a large number of frozen data and the The data underlying the results presented in the study are convenient transfer afterward and use of the IEC available within the manuscript. 61850 report. The service recognizes the real-time operational reporting of abnormal events Conflicts of Interest 6. Conclusion The authors declare that they have no conflicts of interest. 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Research on Model Construction of Electric Energy Metering System Based on Intelligent Sensor Data

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Hindawi Publishing Corporation
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1687-9120
eISSN
1687-9139
DOI
10.1155/2023/1296165
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Abstract

Hindawi Advances in Mathematical Physics Volume 2023, Article ID 1296165, 8 pages https://doi.org/10.1155/2023/1296165 Research Article Research on Model Construction of Electric Energy Metering System Based on Intelligent Sensor Data 1 2 2 2 2 Hang Li, Luwei Bai , Jia Yu, Yongmei Mao, and Zhenzhen Hui Inner Mongolia Power (Group) Co., Ltd., Inner Mongolia Power Research Institute Branch, Hohhot, 010020 Inner Mongolia, China Electric Energy Measurement Supervision Center, Inner Mongolia Power (Group) Co., Ltd., Inner Mongolia Power Research Institute Branch, Hohhot, 010020 Inner Mongolia, China Correspondence should be addressed to Luwei Bai; b20160901216@stu.ccsu.edu.cn Received 23 September 2022; Revised 31 October 2022; Accepted 20 March 2023; Published 3 May 2023 Academic Editor: S. E. Najafi Copyright © 2023 Hang Li et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The informatization construction of the power grid is becoming increasingly popular, business application systems are constantly emerging, and power-related data is rapidly expanding. These discrete power data are scattered in various application systems, and it is not easy to directly provide advanced enterprise applications. The establishment of intelligent power statistical model is an urgent need for constructing power grid informatization. This paper proposes a model of an electric energy metering system based on intelligent sensor data and introduces the existing digital metering system. This model is the integration and promotion of business integration based on the digital metering system. It is the first time to apply new metering equipment, such as measurement and control devices with integrated metering functions, and new metering technologies, such as IEC 61850 electricity meter reading applications. It is hoped that this paper can lay a foundation for further research. 1. Introduction matically generates a report. The actual load verification function can verify the inspected digital electric energy Science and technology have developed rapidly, and the meter at the substation site without affecting the use of the intelligence and informatization are becoming increasingly inspected digital electric energy meter. Various problems, popular in the industrial field. The digital energy meter cal- such as power imbalance, seriously hinder the engineering ibrator can accept the output signal of the standard power, application process of digital metering technology. Accord- and, after AD conversion, use the internal digital energy ing to relevant data statistics, in 2020, among the 10 kV lines meter to calculate the electric energy and output the electric of Wuhan Power Supply Company, the ratio of users with a energy pulse to the higher precision electric energy metering line loss rate of more than 5% was 12.6%, the percentage of equipment to carry out the calibration to achieve the quan- users with a line loss rate of more than 10% was 7.1%, and tity value transmission. Although the accuracy of digital the percentage of users with a line loss rate of more than metering equipment has been significantly improved, there 8% covered by unique transformer customers was 5.3%. are still many problems in actual operation, such as frequent During 2018-2021, more than 20000 defaulters and power communication failures and abnormally large measurement thieves were found, saving more than 80 million yuan of errors under the condition of good equipment performance, economic losses. Currently, the annual loss due to electric resulting in the inability to upload measurements and inac- energy theft in China is up to 20 billion yuan, and the value curate upload data [1, 2]. The virtual load verification func- is increasing yearly. Taking the yearly electricity sales of 70 tion controls the output of the standard power source by billion kWh in a province as an example, if the line loss editing the verification scheme of the electric energy meter, caused by artificial electricity theft increases by one percent- verifies the digital electric energy meter in detail, and auto- age point, the power loss will be up to more than 700 million 2 Advances in Mathematical Physics kWh, equivalent to nearly 400 million yuan [3]. Inductive In traditional substations, the energy metering system con- equipment must absorb active and reactive power from the sists of transformers and electronic energy meters. The trans- power system during operation. Therefore, after installing formers convert high voltage/large current into small voltage/ shunt capacitor reactive power compensation equipment in current signals of 100/57.7 V or 1/5A and then input them to the power grid, it will be able to provide reactive power con- the electronic energy meter [6]. The structure of an electronic sumed by compensating inductive load, reducing the reac- watt-hour meter is similar to that of an induction watt-hour tive power supplied by the power grid side inductive load meter, composed of two parts: a measuring mechanism and and transmitted by the line. To effectively grasp the existing auxiliary components. The measuring instrument is mainly issues in the actual operation of the digital electric energy written as an electronic circuit. Its measuring elements are metering system and to clarify the aspects and contents of composed of a UI multiplier, U/f converter, and counter. The the practical work of digital metering in the next step, the auxiliary components are the same as those of the inductive State Grid Jiangsu Electric Power Company selected Wuxi watt-hour meter. To complete the accumulation of electrical as the research object to investigate the operation of all dig- energy. In the intelligent substation, the electric energy meter- ital electric energy meters under the jurisdiction of its urban ing system has two forms: the firstistouse electronic trans- area. Statistics were carried out, a field investigation was formers, digital input merging units, and digital electric energy meters. The electronic transformers directly output dig- conducted on the application status of the digital electric energy metering system in Xijing intelligent substation, ital quantities, and the subsequent data transmissions all use and valuable first-hand information was obtained [4]. optical fibers. The second is to use traditional electromagnetic The main work done in the paper can be described as transformers still. The analog input merging unit digitizes the follows: (1) introduces the statistics of operating faults of voltage and current signals output by the conventional trans- Wuxi digital electric energy meters and analyzes the possible formers on the spot. This measurement system structure is causes of various spots; (2) taking the digital power measure- adopted because the technology of electronic transformers is ment on the high-voltage side of the main transformer in immature [7]. The configuration principle of the electric energy Xijing No.1 substation as an example, combined with digital metering device includes that the secondary circuit of the volt- measurement; the basic structure of the system points out its age transformer in the electric energy metering device for trade shortcomings in practical applications; (3) this paper sum- settlement above 35 kV shall not be equipped with the auxiliary marizes the current practical problems faced by the power contact of disconnector. The electric energy metering device for metering system based on intelligent sensor data in engi- trade settlement is installed at the user’s place, and the user sup- neering applications and proposes corresponding solutions plying power at 10 kV and below should be equipped with a to provide a reference for the next step in the development national unified standard electric energy metering cabinet or of intelligent power systems. electric energy metering box. To improve the accuracy of low load metering, electric energy meters with the overload of 4 times or more shall be selected. Figure 1 shows the structural 2. Theoretical Analysis on Electric comparison of these three metering systems. Energy Metering W = U × I × t, ð1Þ Electric energy measurement has two main functions: on the one hand, it is used for internal assessment and settlement of or power grid enterprises, and on the other hand, it is used as the basis for trade settlement between power generation, W = P × t, power supply, and electricity consumption [5]. To ensure ð2Þ that the electric energy metering device can accurately mea- W = W + W + W +⋯W : n 1 2 3 n sure the electric energy, first of all, the category of electric energy metering device should be correctly selected. Sec- In the above formula, W represents electric energy, U rep- ondly, choose the electric energy meter and instrument resents the actual voltage value, I represents the actual current transformer with excellent performance and quality, as well value, P stands for electrical power, and t represents the elec- as the secondary circuit wire section, and install and main- tricity consumption time. tain them as required to ensure the safe, accurate, and reli- able operation of the electric energy metering device. 3. Research and Analysis Electric energy measurement accuracy directly affects the internal assessment and analysis results of power grid com- 3.1. Statistical Analysis on Operation of Wuxi Digital Electric panies or the fairness of trade settlements. Therefore, the Energy Meter. Wuxi, Jiangsu, has several smart substations. electric energy measurement system must be accurate and The city with the most extensive range of digital power reliable. The role of electric energy measurement standards metering systems in Jiangsu Province is Wuxi Power Supply in energy conservation and consumption reduction includes Company. The technical advantages of intelligent substa- that scientific and advanced electric energy measurement tions include the following: the smart substation can achieve tools provide accurate data for energy-saving transforma- an excellent low-carbon environmental protection effect, tion, and the analysis of electric energy measurement data and the intelligent substation has good interaction and reli- provides the scientific basis for energy-saving change. ability characteristics. Advances in Mathematical Physics 3 Electronic energy meter Traditional current Traditional voltage transformer Cable Optical fiber Digital energy meter Electronic current Electronic voltage Optical fiber transformer Optical fiber Digital energy meter Figure 1: Structure comparison of three metering systems. Table 1: Statistics by voltage level. Up to now, the total number of digital meters under the jurisdiction of Wuxi city is 251, involving 43 substations of 3 Voltage Total number Number of Failure voltage levels. Among them are three 500 kV substations level (kV) of digital tables failure tables rate (%) involving 32 photoelectric meters, 17 220 kV substations 500 32 1 3.1 involving 91 photoelectric meters, and 23 110 kV substations 220 91 5 5.5 involving 128 photoelectric meters. The intelligent substa- 110 128 39 30.5 tion uses reliable, economic, integrated, low-carbon, and environment-friendly equipment and design, which can support the real-time online analysis and control decision- Table 2: Statistics by fault type. making of the power grid, with the basic requirements of the whole station information digitization, communication Number of Percentage of Fault type fault tables failure table (%) platform networking, information sharing standardization, system function integration, structural design compactness, Battery cannot be uploaded 21 46.7 high-voltage equipment intelligence, and operation status Battery error 9 20.0 visualization. Other faults 15 33.3 This paper mainly conducts statistics on the operation of digital meters in operation under the jurisdiction of the Table 3: Statistics by manufacturer. Wuxi urban area. The failure rate of digital electric energy meters is generally 16%, which is higher than the failure rate The number of of traditional electronic energy meters. To further analyze digital meters Number of Percentage of Manufacturer the operation of the digital electric energy meter, Table 1 is supplied by the fault tables failure table (%) by voltage level, Table 2 is by fault type, and Table 3 is the manufacturer classification statistics of manufacturers. 1 90 2 2.2 From the above data, we can preliminarily summarize 2 74 19 25.7 the following conclusions (Figure 2). It can be seen from 3 36 2 0.56 Table 1 that as the voltage level decreases, the failure rate 4 17 2 11.8 gets higher and higher. Many faults include failure to upload power and power error. The primary responsibility is that 5 9 7 77.8 the administration cannot be uploaded due to communica- 6 5 3 60.0 tion failure; different manufacturers’ digital electric energy meters significantly differ in failure rate. The communica- tion failures of digital watt-hour meters mainly include were further analyzed. A communication failure causes the frame loss, communication delay, and channel abnormality inability to upload the electricity. The judgment is based (Figure 3). on the standard measurement of the electric energy meter, Through exchanges and discussions with relevant tech- but the centralized meter reading center cannot read the nical personnel of the operation and maintenance unit and electric energy. The power error should be the wrong config- on-site inspection, the possible causes of various failures uration of the parameters of the electric energy meter. The Analog input type merging unit Digital input type merging unit 4 Advances in Mathematical Physics The number of digital meters supplied by the manufacturer ple [9]. The idea of single server sharing is to use one PC as the server to provide network-sharing services to other PCs. There are mainly two schemes to realize this method: (1) proxy server scheme and (2) URL conversion scheme. Since Xijing Substation was put into operation, there have been relatively few problems in the digital metering system, but there are still faults, and on-site fault investiga- tion is required. Taking the digital power metering of the high-voltage side of the main transformer of Xijing Substation No. 1 as an example, the schematic diagram of the system structure is shown in Figure 4. 1 4 As shown in Figure 4, the digital energy metering sys- 2 5 tem is very different from the traditional system in struc- 3 6 ture, mainly because the energy meter is no longer directly connected to the transformer, and there are more Figure 2: The digital meter number supplied by the manufacturer. remote modules, photoelectric units, and merging units in Percentage of failure table (%) the middle. The design principles of the electric energy metering system include that the electric energy metering 77.8 system should be designed as an independent and complete 60 system. Electric energy acquisition has low requirements for real time but high requirements for simultaneity, increased requirements for electric energy acquisition accuracy, the 25.7 principle of uniqueness of data source, and the high reliabil- ity of software. The transmission signal has also become a 11.8 digital quantity, switches, and other equipment. From the 2.2 0.56 perspective of on-site operation and maintenance of meter- 1 23 4 5 6 ing, although the wiring is less, the remote modules, voltage-combining units, current-combining units, switches, Figure 3: Percentage of failure table. and other equipment are widely distributed and partially overlap with the automation system in the substation. The basis for the judgment is that the current protection and metering data sources in the intelligent substation are the secondary wiring of the metering system becomes less clear, making the whole system more complex. As electric energy same. If the data source is incorrect, the protection device should respond first. Other faults mainly refer to the crash is a cumulative value, even small errors will reach an of the electric energy meter, black screen, no indicator light, incredible degree after accumulation. For both the seller etc. The cause of such failures is defective software or hard- and the user of electricity, this cumulative value is an eco- ware of the electric energy meter itself. nomic loss. Therefore, the selection principle of measure- ment accuracy should be that the greater the capacity, the 3.2. Investigation of the Fault Situation of Digital Electric higher the accuracy. It is better to use energy meters with Energy Metering in Xijing Substation. Xijing Substation is an accuracy of 0.2 level and above for large-capacity power plants and transmission lines. the first batch of pilot projects for intelligent substations of the State Grid Corporation of China. Construction started During the on-site investigation of the digital power in July 2010 and was put into operation in December of metering fault on the high-voltage side of the main substa- the same year. The station is an intelligent substation in a tion of Xijing Substation No. 1, it was difficult for traditional complete sense. The operational characteristics and respon- substation operation and maintenance personnel to locate sibilities of intelligent substations make them have good and analyze the fault. In contrast, professional technicians interactivity. It is responsible for the data statistics of power familiar with digital power metering could infer the fault grid operation, which requires it to feed back safe, reliable, point and cause. Substation operation and maintenance accurate, and detailed information to the power grid. After experiences are also difficult to verify and figure out. In addi- the intelligent substation realizes the function of information tion, because the digital power metering system and the automation system in the substation have some overlapping collection and analysis, it can not only share the data inter- nally but also interact well with more complex and advanced equipment, such as merging units and switches, the equip- systems in the network. It adopts the design of “three layers ment focal point is not clear, which makes troubleshooting and two networks.” The SV, GOOSE, and IEEE 1588 net- very difficult. The problem-solving efficiency is low, so the works share the transmission network, and the dual network coordination and cooperation of multiple departments are required to complete the work [10]. The electric energy is redundant [8]. The voltage and current measurement equipment all uses electronic transformers. The current acquisition device is the communication center of electric transformer is based on the optical principle, and the voltage energy data. On the one hand, it collects and stores the elec- transformer is based on the capacitive voltage divider princi- tric energy data output by the digital electric energy meter in Advances in Mathematical Physics 5 ECT Remote module EVT FT3 Line current Photoelectric unit merge unit ECT EVT Switch Remote Line voltage module merge unit Meter ECT EVT Automatic meter Remote reading module center Figure 4: Xijing Substation No. 1 main transformer high-voltage side digital electric energy metering. the form of serial communication. On the other hand, the relay protection and measurement and control automation collected electric energy data is transmitted to the master system. The method of the electric energy metering system station of the electric energy billing automation system is only at the functional level [11]. For example, in terms through the uplink channel. of synchronization time synchronization, some use IRIG-B code time synchronization, and some use IEEE 1588 time synchronization, while the “direct sampling and direct hop- 4. Problems Faced by Digital Energy Metering ping” protection does not depend on time synchronization. Through the research on the application of digital energy Some sampling devices do not even access the time synchro- metering in Wuxi, Jiangsu Province, and combined with nization signal, relying entirely on interpolation synchroni- zation, and the data source of the energy meter comes the actual situation of digital metering technology, the prob- lems that still exist in trade settlement are divided into three from the switch. In this extreme case, even if the errors of the various components of the power calculation system aspects; are acceptable, the overall measurement error will exceed 4.1. Normative. The meaning of normative includes the nor- the tolerance. mativeness of the metering system structure and the norma- While for the Department of Metrology, due to the lim- tiveness of metering equipment management. The intelligent itation of majors and responsibilities, most universities and electricity meter can realize accurate and real-time cost set- scientific research institutions mainly focus on the research tlement information processing, simplifying the complex of measurement accuracy and traceability technology. process of past account processing. In the power market The normative aspect of statistical structure has not been environment, dispatchers can switch energy retailers more paid enough attention to, so the design of the current digital timely and conveniently and even realize fully automatic measurement system is not unified, which affects the accuracy switching in the future. At the same time, users can also of measurement and the reliability of measurement data. obtain more accurate and timely energy consumption and (2) Management normative accounting information. There should be a unified management specification to (1) Structural normative ensure that the digital energy metering system is accurate, Electric energy metering not only requires correct func- stable, and reliable. Traditional energy metering systems, tions, especially the electric energy metering system used according to DL/T 448-2000 “Technical Management Regu- for trade settlement, but also conforms to national manda- lations for Electric Energy Metering Devices” and SD 109- tory requirements. 1983 “Inspection Regulations for Electric Energy Metering In the process of intelligent substation design, the design Devices,” strictly stipulate the classification of metering unit mainly focuses on the stability and reliability of the points, metering device configuration, procurement, 6 Advances in Mathematical Physics installation, weekly inspection, and other links, so traditional electric energy metering systems. For example, when there electric energy metering system can measure electric energy is a fault that cannot be transmitted back to the electricity, accurately, stably, and reliably. However, no mandatory or the cause of the defect cannot be determined, and the fault recommended standard documents for managing digital point cannot be located. The most common fault in the sur- energy metering systems exist. After the digital metering sys- vey is the failure to send power back. Due to the numerous tem is put into operation from the infrastructure, there is causes of such marks and the enormous scope involved, it almost no management department, and its acceptance is is challenging to locate the spot. In response to this problem, also completed by the automation professional. In addition, related testing equipment should be developed. In Jiangsu, the follow-up operation and maintenance of the digital the electric energy accumulated by the user’s intelligent energy metering system are also tricky. The data on water, meters is collected by the local collection terminal. Then, gas, and heat consumption collected by smart meters can the electric energy is read by the remote server. Therefore, be used for load analysis and prediction. The total energy the equipment that detects the power that cannot be consumption and peak demand can be estimated and pre- returned on-site should have the following functions: dicted by comprehensively analyzing the above information, (1) Simulate the local acquisition terminal to check load characteristics, time changes, etc. This information will whether the communication function of the electric provide convenience for users, energy retailers, and distri- energy meter is in good condition bution network dispatchers; promote rational power use, energy conservation, and consumption reduction; and opti- (2) Simulate the remote server to check whether the func- mize grid planning and dispatching. (1) Up to now, there is tion of the acquisition terminal is in good condition neither detection equipment nor detection basis and means for judging the failure of digital electric energy metering (3) The simulated negative control center sends a meter equipment; (2) there are no relevant technical normative reading instruction to check whether the remote documents on how to deal with the disappointment after server can be accessed commonly the occurrence of the fault; and (3) the digital power meter- 4.3. Quantitative Traceability. For a digital energy metering ing system and the substation automation system have system to be used for trade settlement, value traceability is some overlapping equipment, and it is necessary to coordi- one of the problems that must be solved. The value trace- nate multiple departments to carry out the daily operation and maintenance of the metering system. By feeding back ability research related to digital energy metering includes three aspects: the energy consumption information provided by smart meters to users, users can be encouraged to reduce energy (1) High-precision digital energy metering algorithm consumption or convert energy utilization methods. For households equipped with distributed generation equip- (2) A high-accuracy digital power source generation ment, it can also provide users with reasonable power gen- method eration and electricity use schemes to maximize the interests of users. (3) Traceability of digital quantities to analog quantities. Under the current situation of the lack mentioned above There have been many studies on the first two prob- of normative management, it is impossible for the digital lems, and there is no recognized perfect solution for electric energy metering system to operate as accurately, sta- the third bly, and reliably as the traditional electric energy metering system. In response to this problem, the design, operation 5. Electric Energy Metering System with and maintenance, marketing, and other relevant depart- Intelligent Sensor Data ments should be coordinated to formulate a multiparty rec- ognized smart substation digital energy metering system 5.1. Electric Energy Metering System Model of Intelligent design and operation and maintenance plan, including sys- Sensor Data. At present, there is no research on electric tem wiring, equipment management, and equipment inspec- energy metering system models based on intelligent sensor tion, to form technical normative documents be enforced. data at home and abroad. For the sake of realizing the meter- ing data’s standardization and ensuring the interoperability 4.2. Detection Capability. In terms of laboratory testing, sev- and interchangeability of various devices in the metering eral testing standards, including electronic transformers, system, the following extensions are made on the premise merging units, and digital energy meters, have been formu- of analyzing the research function of the model about power lated concerning traditional electric energy metering equip- metering, demand calculating, freezing, incident report, ment, and corresponding testing platforms have been time-sharing, and segmented metering which can be clearly developed or established. Although imperfect, it can guaran- shown in Figure 5. tee the stable and reliable operation of the digital electric energy metering system under reasonable operating condi- (1) The extended model logic node MMTR is used for tions. However, there are still deficiencies in an on-site forward and reverse active energy and four- inspection. It has also been mentioned that there is a lack quadrant reactive energy and demand measurement of detection equipment and related technical specification (MMTR for three-phase electric energy meters, documents for the current on-site fault detection of digital MMTN for single-phase electric energy meters). Advances in Mathematical Physics 7 Mod INC METR LLN0 Beh INS LPHD Health MTST Namplt LPL MMTR EEhealth ISI MMXU MTUV FwdWh MTOV BCR QIVarh MTOC FwdW MTUC Q3VarFn MV GGIO PhsFwdW WYE IARC PhsTotVar PhsQ4Var Figure 5: Smart energy metering model. Under different conditions, such as electricity meter- programming, the demand cycle programming, the ing MMTR1 and demand metering MMTR2, they energy meter clearing, the demand clearing, the are distinguished by Arabic numerals suffixes event clearing, the opening of the meter cover, and opening the button box (2) The original MMXU logic node is used for remote (6) Create a new MTST logical node to save and record measurement of voltage and current (MMXU for the time zone period table three-phase watt-hour meter and MMXN for single-phase watt-hour meter) (7) Take rated voltage and current, active or reactive combined status word, energetic energy pulse con- (3) Since metering has different limits for voltage loss, stant, reactive energy pulse steady, and other energy phase loss, and current loss and protection measure- meter asset information as the extended data object ment and control alarm limits, new MTUV, MTOV, of the symbolic logical node LLN0 MTUC, and MTOC are created to complete the mon- itoring and alarm functions. Different alarms of the 5.2. Characteristics of Electric Energy Metering System Based same type of event alarms are designed with other on Intelligent Sensor Data instances, respectively, such as undervoltage MTUV1 and undervoltage MTUV2; different models are dis- (1) With the design inspiration of simplifying the com- tinguished by Arabic numeral suffixes munication network in the station, we adopt a tech- (4) Using the original logic node GGIO, there is no need nical solution that combines all-digital computing to set customized alarm events such as sampling systems and computing services with other special- abnormality, watt-hour meter failure, power failure, ties. The private communication network in the and voltage reverse phase sequence measurement system station is merged into the pub- (5) Using the original IARC recording, the program- lic communication network based on IEC 61850. ming events, for example, the time zone timetable The measurement service shares data sources and 8 Advances in Mathematical Physics (4) Standardization. For the content of the digital simu- hardware resources with other majors which sim- lation module architecture, it is required to comply plifies the secondary system in the station and lays a foundation for improving the intelligence level of with the standards issued by the relevant national departments, applicable international regulations, the measurement system corresponding industry requirements, and the provi- (2) According to the measurement business needs, the sions of pertinent power organizations to ensure the measurement is subdivided into three categories: accuracy and standardization of the system simula- assessment, settlement, and measurement points tion data. Distinguish the characteristics of metering that may be converted into settlement points. Differ- devices in different cities and counties. Conduct dig- ent metering points design various implementation ital simulation modeling of electric energy metering schemes and propose other technical conditions devices based on the principle of “unified standard, unified platform, and unified implementation” (3) The IEC 61850 node and service model are estab- lished for the new generation of intelligent substa- tion metering and metering management. The IEC Data Availability 61850 file service is used to realize the real-time recording of a large number of frozen data and the The data underlying the results presented in the study are convenient transfer afterward and use of the IEC available within the manuscript. 61850 report. The service recognizes the real-time operational reporting of abnormal events Conflicts of Interest 6. Conclusion The authors declare that they have no conflicts of interest. 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Advances in Mathematical PhysicsHindawi Publishing Corporation

Published: May 3, 2023

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