Summary: Analyzed the research status of remote metering and control electric energy meters at home and abroad. Based on the functional requirements and parameter specifications of remote metering and control electric energy meters, designed and researched such meters. From the perspective of functional segmentation, modularized design was applied to the hardware circuit system of the electric meters. Conducted research on the functional software of the meters, achieving metering, recording, monitoring collection, and communication functions. Commands can be issued by the master station system to control the remote metering and control electric energy meters. Test results show that the remote metering and control electric energy meters based on smart cards have achieved active uploading of electric energy data, which aids the master station system in remotely monitoring electric energy data through the meters.
Keywords: Smart Card; Smart Electricity Meters; Remote Fee Control; Power Consumption Information Collection; Fee Control Strategies; Narrowband Internet of Things
Introduction
The electricity sector, an indispensable part of China's economic development, holds a crucial position. The quality of supply, service level, and service model upgrades of power companies have become the main directions for the development of the electricity industry. With the prevalence of informatization, comprehensive electricity coverage and cost control have gradually become important goals for China's electricity industry. The billing and charging systems of power companies are beginning to shift towards intelligence. The United States proposed the "Grid 2030 Plan" in 2003, aiming to promote the construction of smart grids, achieve digital power supply services, and build the first smart grid city in Colorado. The European Union, based on a set of energy policies, actively promotes the development of green energy. The smart grid in the EU relies on various terminals to monitor electricity use in public departments and office buildings, gradually changing customer habits. China is also actively developing and deploying related projects in the smart grid field. China's power grid takes ultra-high voltage grids as the backbone, with different levels of grids working in synergy to implement the "Three Integrations and Five Enhancements" work deployment. China's power grid industry is accelerating industrial transformation and upgrading, achieving comprehensive remote cost control of electricity meters.
Key Technology for Remote Energy Consumption Control Meters
1.1 Overview of Remote Energy Control Meters
Remote metering electricity meters typically include functions such as data collection, data transmission, electricity measurement, data reset, data storage, data freezing, and event recording and alarms. For instance, the electricity measurement function for three-phase power consumption often involves measuring three-phase current, voltage, and frequency, and also includes the feature of custom rates. Remote metering electricity meters can effectively define rates for different time periods and time zones, and are equipped with electricity consumption monitoring capabilities, recording recent events such as voltage drops, overvoltages, power outages, and power-on alarms.
1.2 Intelligent Wireless Communication Technology
Our energy meter communication control network employs wireless communication technology based on narrowband Internet of Things (NB-IoT). The system link of NB-IoT typically consists of an uplink and a downlink. The NB-IoT system studied in this article eliminates the downlink channel link. The uplink network uses phase-shift keying (PSK) modulation and transmits data via single-carrier frequency division multiple access technology. To enhance coverage, the subcarrier spacing is usually set at 3.75 kHz, with data transmission rates ranging from 160 kbit/s to 200 kbit/s. This network is primarily based on the 4G LTE communication architecture, capable of meeting the demands of low power consumption and large-scale connections, and enables direct transmission of user energy data to the provincial main station system on the NB-IoT network. NB-IoT can be deployed across various wireless frequency bands, categorized into independent deployment, protected band deployment, and in-band deployment. The architecture of the NB-IoT IoT platform is illustrated in Figure 1.
Hardware Principle and Design of the 2-Remote Power Consumption Control Electricity Meter
2.1 Features and Parameters of the Remote Energy Control Electric Meter
The remote metering electricity meter features metering, recording, monitoring, and communication functions. In addition to electricity metering, it allows for rate setting and measurement of power, voltage, current, frequency, phase angle, power factor, and apparent power. The communication function is based on NB-IoT technology, with a narrowband (NB) communication module providing AT commands for data query. After each network connection, the NB communication module automatically records data traffic until the connection is disconnected. The working frequency band and antenna interface characteristic impedance parameters are listed in Table 1, with a broad coverage frequency range. The electricity meter generates alarm messages for events exceeding the threshold and relies on communication technology to transmit monitoring and stored data to the cloud platform.
2.2 Hardware Principle of Remote Energy Consumption Control Electric Meters
When designing the hardware system for the remote metering and control electric power meters, it is necessary to categorize them based on their functions. The hardware architecture of the electric power meters includes signal processing modules, electric power measurement modules, NB-IoT communication modules, and peripheral circuit modules. The basic hardware architecture of the remote metering and control electric power meters is shown in Figure 2. These modules are composed of hardware circuits and their functions are realized by corresponding software programs. The power supply module powers the various sub-modules, while the auxiliary power supply is used to prevent the normal monitoring function of the electric power meter from being affected by the failure of the main power supply.
2.3 Module Design of Remote Energy Control Electricity Meters
When designing critical circuit modules, the basic architecture of the remote metering electricity meter should be considered. The remote metering electricity meter's signal processing module primarily relies on the data acquisition ADC module for sampling. The sampling function is illustrated with the current sampling circuit, which converts the phase currents. The basic principle is to use current transformers, grounding one side of the circuit and connecting the other side to the system to complete the sampling. The specific schematic diagram is shown in Figure 3. Since the requirement for the metering chip is to ensure a 2.5mA current amplitude, this sampling circuit can convert a 5A current into a 2.5mA current, achieving the current-voltage conversion.
The measurement function module is centered around the ADE7878计量 chip, which boasts powerful functionality and excellent signal processing capabilities. This chip exhibits significant advantages in measuring the effective values of voltage and current for electricity meters, as well as measuring active and apparent power. The normal, power-saving, and low-power modes of the chip fully meet the energy-saving and consumption-reduction requirements of electricity meters. The input voltage variation range of the chip is -0.5 to 0.5V, with a crystal oscillator frequency of 16.4MHz. The RSET pin is the reset input pin, while the CF1 and CF3 pins are the logic output pins for frequency calibration. The CF1 and CF3 pins complete the frequency calibration logic output function. The basic circuit diagram of the measurement chip is shown in Figure 4.
The NB-IoT wireless communication module utilizes the BC95-B5 communication module from Yate Loong Co., Ltd., featuring ultra-low power consumption. The receiving frequency is maintained at 869 to 894 MHz, while the transmitting frequency ranges from 824 to 849 MHz. This module supports expandable serial ports and embedded subscriber identity module (eSIM) card interfaces, among other application interfaces. Internally, the module includes Flash and static random-access memory (SRAM), as well as radio frequency circuits and eSIM card socket circuits. The voltage reduction and stabilization circuit of the wireless communication module is shown in Figure 5.
The smart card for the electricity meter communicates via an embedded eSIM card, eliminating the need for the traditional plug-and-play subscriber identity module (SIM) card. This enables direct communication with the electricity meter. By binding the eSIM card to the electricity meter, data items are expanded on the basis of the 645 protocol, and the eSIM card number (i.e., the phone number) is pre-written into the meter at the factory. Reading is then performed through the expanded 645 protocol. The eSIM card measures 6mm x 5mm and is soldered onto the circuit board using an external sticker method, facilitating maintenance and replacement in case of eSIM card failure, and making it easier to manage the inventory details of the electricity meter and eSIM card.
Design of the Software Architecture for 3-Phase Remote Energy Control Meters
3.1 Architecture and Program Design
The software architecture design of the electrical energy meter is entirely based on the hardware circuit system. It first designs the core main program, followed by the design of the sub-programs for each module based on the core main program, as shown in Figure 6.
The remote metering sub-program for energy control meters is primarily used for reading real-time clock data and for metering electricity consumption in stages at the user end. In terms of energy metering, the sub-program must separately meter active and reactive energy, featuring both forward and reverse active energy metering capabilities, allowing for the setting and combination of active energy; reactive energy can be set as the sum of any four quadrants and can also be set and combined. The signal processing program first requires the energy meter user to undergo a safety authentication; next, it initializes the energy meter according to the initialization command, selects the metering mode; then it activates the wireless communication function, remotely receives commands, and displays the results on the LCD after reading the chip data. The flowchart of the remote metering sub-program for energy control meters is shown in Figure 7. In terms of metering and control, it can achieve both remote and local control functions. When the amount on the energy meter is less than the set alarm amount, the LCD screen of the energy meter will display a message or the alarm light will illuminate, reminding the user to pay their electricity bill.
Our wireless communication subroutine is a crucial design component. The NB-IoT network utilizes eSIM smart cards for wireless communication. Based on the existing communication protocols for remote metering electricity meters, we have established the data transmission frame format, data encoding, and transmission rules between the system master station and the electricity meter. Data exchanges occur between the remote metering electricity meter and the collection system during different communication light flashes, as illustrated in Figure 8.
3.2 Feature Testing
Based on the fundamental function experiments of the remote metering electrical energy meter with eSIM smart cards, the focus is primarily on expanding the core functions of the electrical energy meter. These function experiments are basically in line with the established requirements for remote metering electrical energy meters. To ensure that the basic functions of the remote metering electrical energy meter meet the operational needs for formal launch, the Internet of Things (IoT) system of the master station is used to control the electrical energy meters. An integrated asset management system based on IoT meter collection and communication is achieved, with the basic experimental project results shown in Table 2.
Ultimately, the system architecture diagram of the remote fee control electricity meter is as shown in Figure 9. By implementing the remote fee control electricity meter solution, it can directly interact with the master station via NB communication. The remote fee control electricity meter achieves active upload of electricity data, enabling real-time monitoring of electricity data and reducing the operational collection pressure on the master station system.
4 Acrel-3000WEB Energy Management Solution
4.1 Overview
Consumers account for 80% of the total electricity consumption in the power grid. Intelligent electricity management at the consumer end is of great significance for reliable, safe, and energy-saving electricity use. Constructing an intelligent electricity service system and promoting solutions for electricity management using smart meters and intelligent electricity management terminals, etc., achieves a positive and reciprocal interaction between the power grid and consumers. The urgent research topics at the consumer end mainly include: advanced meters, intelligent buildings, smart appliances, value-added services, customer electricity management systems, and demand-side management.
The Acrel-3000WEB Energy Management Solution from Ankeai meticulously segments and analyzes energy consumption at the user end, presenting managers or decision-makers with intuitive data and charts detailing the usage and consumption of each energy category. This facilitates identification of high-energy consumption areas or inefficient energy use habits, effectively conserving electricity. It also provides accurate data support for users to further implement energy-saving improvements or equipment upgrades.
4.2 Application Scenarios
(1) Office Buildings (business offices, large public buildings, etc.)
(2) Commercial Buildings (malls, financial institution buildings, etc.)
(3) Hospitality & Tourism Architecture (hotels, restaurants, entertainment venues, etc.)
(4) Educational, Cultural, Scientific, Health, and Sports Architecture (including cultural, educational, scientific research, medical and health, and sports buildings, etc.)
(5) Telecommunications Infrastructure (postal, telecommunications, broadcasting, television, data centers, etc.)
Transportation infrastructure construction (airports, railway stations, port buildings, etc.).
4.3 System Architecture
4.4 System Features
1) Real-time Monitoring
The system features a user-friendly human-machine interface, displaying the operation status of the distribution lines in the form of a single-phase distribution diagram. It provides real-time monitoring of electrical parameters such as voltage, current, power, power factor, and energy for each circuit. It dynamically supervises the on/off status of circuit breakers, disconnecting switches, and earth switches for each distribution loop, as well as relevant fault and alarm signals.
2) Electricity Statistics Report
The system supports the integrity of the metering system with a rich set of reports. It features a scheduled meter reading and summary statistics function, allowing users to freely query the power consumption status of any distribution nodes within any time period since the system has been running normally. This includes the analysis of the power consumption statistics between the incoming lines of each node and the power consumption of various branch circuits. This function ensures visibility and transparency in power usage and enables analysis and traceability in cases of significant consumption errors, thereby maintaining the accuracy of the metering system.
3) Detailed Electrical Parameter Inquiry
In the primary distribution diagram, when the mouse cursor hovers near each loop, it changes to a hand icon. A single click allows you to view detailed electrical parameters of the loop, including three-phase current, three-phase voltage, total active power, total reactive power, total power factor, and forward active energy. Additionally, you can view 24-hour phase current trend curves and 24-hour voltage trend curves.
4) Operational Reports
The system features real-time and historical power parameter storage and management capabilities. All real-time collected data and sequential event records can be saved to the database. Users can customize the parameters, time, or select updated records for querying in the search interface, and the results are displayed through reports. Users can tailor daily and monthly reports as needed, support exporting in Excel format, and can also export in PDF format upon request.
Transformer Operation Monitoring
The system provides real-time online monitoring of the operating status of the main power entry, main transformer, and critical load output lines. It displays operational trends such as current, transformer operating temperature, active power demand, active power, apparent power, and transformer load factor through curves. This analysis of transformer load factor and losses facilitates timely understanding of operating levels and power demand by maintenance personnel, ensuring safe and reliable power supply.
6) Real-time alerts
The system features real-time alarm capabilities. It can monitor and alert on events such as the change in remote signaling of circuit breakers, disconnecting switches, earthing knives, and their operations, protective actions, tripping due to accidents, as well as over-limit conditions of voltage, current, power, and power factor. Upon an alarm, the system automatically pops up a real-time alert window and emits an audible or voice reminder.
7) Historical Event Inquiry
The system is capable of storing and managing records of remote signal changes, protection actions, fault trips, as well as events such as voltage, current, power, and power factor limits. This facilitates users in historically tracing system events and alarms, conducting inquiries and statistics, and accident analysis.
8) Power Quality Monitoring
The system can continuously monitor the power quality within the entire distribution system range. Operation and maintenance personnel can use harmonic analysis bar graphs and reports to grasp the voltage, current harmonic distortion rate, harmonic content, and voltage unbalance degree of incoming lines, transformers, and important circuits, enabling timely measures to be taken to reduce harmonic losses and minimize abnormal conditions and accidents caused by harmonics (This feature requires an optional power meter with harmonic monitoring capabilities; it can be deleted if not needed.).
Remote Control Operation
The system supports remote control operations for circuit breakers, disconnecting switches, and earthing knives. It features strict password protection and operational permission management functions. For each remote operation, the system automatically generates operation records, including the operator's name, operation time, and type. To achieve this function, the circuit breaker itself must have an electrical control mechanism, and the protective and monitoring control device must support remote control capabilities.
User Permission Management
The system has been equipped with user permission management to ensure secure and stable operation. User permission management prevents unauthorized operations (such as modifications to distribution loop names). Different levels of user login names, passwords, and operational permissions can be defined, providing reliable security for the system's operation, maintenance, and management.
11) Communication Status Diagram
The system supports real-time monitoring of communication statuses of all devices connected to the system, fully displaying the entire network structure of the system. It allows for online diagnosis of device communication statuses, automatically displaying faulty devices or components and their respective failure locations on the interface in case of network anomalies. This facilitates operations and maintenance personnel in real-time monitoring of communication statuses of all devices on-site, enabling timely maintenance of devices experiencing issues, and ensuring the stable operation of the system.
Video Surveillance
Video surveillance displays the live feed (video streaming). Select a specific substation transformer, and you can view the video information within that substation.
13) User Reports
The User Report Page is primarily used to automatically compile a monthly operational data summary for selected transformer substations, including transformer load, power consumption of distribution circuits, power factor, and alarm events, for statistical analysis.
14) APP Support
The mobile power operation and maintenance app supports five major modules: "Monitoring System," "Equipment Records," "Pending Tasks," "Inspection Records," and "Defect Records." It offers functionalities such as single diagram, demand, power consumption, video, curves, humidity and temperature, year-on-year and month-on-month comparisons, power quality, and various event alarm queries. It also includes equipment records searches, pending task handling, and inspection record inquiries.
5 Closing Remarks
This remotely controlled electricity meter designed by our company has achieved functions such as data collection, storage, measurement, and upload, providing a new solution for smart card-based electricity meter design. However, during the testing phase, some unstable factors in the long-term operation stability and reliability of the remote electricity meter were identified, mainly manifested in occasional disconnection of the terminal, which prevents the master station system from collecting data from the terminal, thus making it impossible to accurately calculate electricity consumption. Future improvements are needed to enhance the stability of electricity meter data collection to meet the development requirements of remote electricity control intelligence; under the conditions of meeting national standards and specifications, the operational needs must also be satisfied.
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- Ankorri Enterprise Microgrid Design and Application Manual, 2022.05 Edition
