Abstract: Given that the main energy consumption of public buildings is concentrated in the low-voltage terminals, it is essential to install energy metering devices in the low-voltage power distribution system of public buildings to achieve quantitative management of energy consumption by end users. This paper introduces a digital multi-rate energy meter using fieldbus and a practical case of an energy management system based on this meter to achieve energy management.
Keywords: DDSF1352/DTSF1352 electricity meter; power management system; energy consumption monitoring system
0 Introduction
The "Regulations on Energy Conservation in Public Institutions" (Decree No. 531 of the State Council of the People's Republic of China), signed by Premier Wen Jiabao, was adopted at the 18th Executive Meeting of the State Council on July 23, 2008, and came into effect on October 1, 2008. Article 14 of the Regulations clearly stipulates that public institutions shall implement an energy consumption metering system, distinguishing between energy types and energy systems to implement separate, categorized, and itemized energy consumption metering, and monitor energy consumption to promptly identify and correct energy waste. Document No. 277 of 2006, "Technical Measures for Design of Civil Building Engineering Nationwide - Energy Conservation Chapter: Electrical Volume," proposed that electrical circuits should be equipped with electricity metering devices. Jiangsu and Shanghai also issued Document No. 217 of 2007, "Regulations on Energy Metering Design of Public Buildings in Jiangsu Province," and Document No. 828 of 2008, "Notice on Further Strengthening the Technical Management of Energy Conservation Design for Civil Building Equipment in This City," respectively. These documents further clarified that major electrical facilities should be metered separately, and that metering for office buildings, shopping malls, dormitories, etc., should be done down to the economic accounting unit; and that metering for medical wards, hotel rooms, and school classrooms should be done by floor or functional area, etc., and these requirements should be included in the standards for reviewing drawings and completing acceptance.
Currently, the installation of terminal electricity meters generally adopts the traditional wall-mounted installation method, which has disadvantages such as large size and inconvenient installation. In contrast, the DDSF1352/DTSF1352 DIN rail mounting meter adopts a modular design, offering advantages such as small size, easy installation, and easy networking, facilitating the metering of terminal power distribution energy. This also facilitates the retrofitting of power distribution systems with additional electricity meters.
1. Introduction to DDSF1352/DTSF1352 Electricity Meters
1.1 Product Features
The DDSF1352/DTSF1352 single-phase and three-phase electronic multi-rate electricity meters are mounted on a DIN 35mm rail. They feature a modular design with widths matching miniature circuit breakers, offering 4 and 7 modules respectively, allowing for easy installation in lighting boxes (see Figure 1). The maximum single-connection current is 20 (80) A; currents above 80 A require an external current transformer (CT). The maximum transformation ratio can be expanded to 6000/5A. The meter has an RS485 communication interface and supports the MODBUS-RTU protocol or DL/T645 standard. The transparent flip-top on the terminals and the outer casing can be sealed with lead to prevent electricity theft. Besides being used for internal energy metering and assessment management within enterprises and institutions, this meter can also be used as a trade settlement meter after passing testing and verification by the power supply department. This product complies with GB/T 17215-2002 "Class 1 and Class 2 Static AC Active Energy Meters" and GB/T 15284-2002 "Special Requirements for Multi-Rate Electricity Meters," among other standards.
Figure 1. Electricity meter appearance and installation method
1.2 Design Principles
1.2.1 Design Principle of Single-Phase DDSF1352 Electricity Meter
The DDSF1352 single-phase multi-tariff energy meter is designed using Analog Devices' latest ADE7169F16 system-on-a-chip (SoC). The ADE7169 integrates a high-precision metering unit module, an 8052 MCU, and its peripheral modules. The metering module offers high accuracy, measuring phase current, RMS voltage, active power and reactive power of each phase and the total, grid frequency, and other operating parameters, with a large overload capacity. The on-chip 8052 MCU includes 16K FLASH and 512B RAM, along with various peripheral modules, supporting low-power temperature-compensated on-chip RTC, LCD driver, power management, SPI/I2C interface, and UART communication modules. A single ADE7169 chip is sufficient to design a single-phase multi-tariff multi-function energy meter. The specific design block diagram is shown in Figure 2.
Figure 2. Block diagram of single-phase DDSF1352 meter
1.2.2 Design Principle of Three-Phase DTSF1352 Electricity Meter
The DTSF1352 three-phase electronic multi-rate energy meter is implemented using the ATT7030A metering chip and Freescale's 8-bit microcontroller M68HC908LJ12. Its principle is as follows: real-time voltage and current on the line are coupled through a high-precision current transformer, sampled by the sampling circuit, and sent to the dedicated energy metering chip ATT7030A (which converts the signals into digital signals via an A/D converter, processes them through an on-chip dedicated DSP, and outputs energy pulses). These pulses are then sent to the MCU, which performs time-of-use active and reactive energy metering and maximum demand calculation according to pre-set time periods, processes the data accordingly, and stores it in the EEPROM. Simultaneously, it realizes display and output, and RS485 serial data transmission. The specific design block diagram is shown in Figure 3.
Figure 3. Block diagram of the three-phase DTSF1352 meter.
2 Application Cases
2.1 One-time plan
Taking a student dormitory building at a university of science and technology as an example. The building has four floors, with 24 dorm rooms on each floor, equipped with public restrooms, laundry rooms, and public bathrooms. The primary electrical scheme is shown in Figure 4. The main distribution box's incoming circuit is equipped with a panel-mounted ACR230ELH multi-functional power meter to measure the total electricity consumption of the dormitories. This includes 34 electrical parameters, such as three-phase active power, reactive power, power, power factor, current, voltage, frequency, and phase-specific power consumption. It also measures and analyzes the 2nd to 31st harmonic components of current and voltage, current and voltage imbalance, and positive and negative zero-sequence components of current and voltage. Each floor, emergency lighting, fan, and reserved electrical trunk line are each measured by seven DTSF1352 meters for three-phase active power. These meters can be installed in parallel with CM1 circuit breakers via DIN rail mounting, or centrally mounted above the box. The electricity consumption of each dormitory room, public restroom, laundry room, and corridor on each floor is measured by 27 single-phase DDSF1352 meters, while the public bathroom is measured by one three-phase DTSF1352 meter.
Figure 4. Primary electrical system plan for the dormitory building
2.2 System Networking
The primary distribution system diagram shows the number of branches in the main distribution box and the lighting distribution box on the first floor of the dormitory, as well as the model of the electricity meter for each branch. To meet the needs of intelligent monitoring and remote automatic meter reading, the power management system adopts an RS485 bus to centrally network one ACR230ELH multi-function power meter installed on the main distribution box AL1 main incoming line, 11 DTSF1352 three-phase DIN rail meters installed on WL1~WL7 and in the public bathrooms on each floor, and 108 DDSF1352 single-phase DIN rail meters installed on each floor of the dormitory building (27×4 floors). The monitoring center is equipped with a monitoring computer, printer, communication server, and necessary auxiliary equipment, and the power management system EMS software is installed to complete the remote acquisition and centralized processing of data from each electricity meter. The power management system diagram is shown in Figure 5.
Figure 5 System networking scheme
2.3 Functions of the Power Management System
2.3.1 Remote electrical parameter measurement.
The system successfully acquired real-time electrical parameters from the ACR230ELH multi-functional power meter for the main incoming line, including three-phase current, voltage, power, power factor, active energy, reactive energy, and frequency, which were displayed on the main power management screen. It also enabled remote automatic meter reading for 11 DTSF1352 three-phase meters and 108 DDSF1352 single-phase meters. Furthermore, it automatically calculated daily and monthly electricity consumption for each dormitory and performed energy allocation calculations. The system's integration with field instruments demonstrated hierarchical, categorized, and individual metering management of the main incoming line, branch lines, and end users. (See Figure 4). The ACR230ELH diagnoses power quality issues such as current harmonics and imbalance in the dormitory building, and the system saves historical records, providing a basis for decision-making regarding future power quality improvement plans.
2.3.2 Operational status monitoring.
The administrator can set the system's data collection frequency, such as collecting data every 15 minutes, and set the power load value for each circuit (e.g., 6-10A for dormitory load). The system can process the collected values according to the settings and provide audible and visual alarms for overloaded circuits, alerting the administrator to the abnormal status of that circuit. The system can also perform self-detection of communication anomalies in each circuit, enabling maintenance personnel to troubleshoot and repair in a timely manner.
2.3.3 Trend Analysis.
The system categorizes and identifies collected electrical parameters, storing necessary parameters in a database. Data storage for all electrical parameters can last for up to two years, and for power parameters, it can last for over three years. Storage time can be adjusted according to user needs and hardware configuration. The system provides both real-time curve and historical trend analysis interfaces. The real-time curve interface for relevant circuits can be used to analyze the current operating load status of those circuits. The historical trend view allows users to view the historical trends of all stored data and display various curves, facilitating quality analysis of the monitored power distribution system by engineers. Examples include: current trend, power trend, and harmonic trend analysis of the main incoming line; monthly power consumption trends, bar charts/line charts for branch circuits, etc. It can also compare data with the same period last year/the year before to generate a metering database.
2.3.4 Report printing.
The system can design various types of reports to meet user needs, such as real-time reports, historical reports, event fault and alarm record reports, and operation log reports. It can query and print all data values recorded by the system, and automatically generate daily, monthly, quarterly, and annual electricity reports. It generates electricity rate reports based on the time period and rate settings of the multi-rate system. The starting point, interval, and other parameters for querying and printing can be set manually, and billing reports are automatically generated for internal billing management.
2.4 Project Cost
Based on the initial plan and system structure, the material names, models, quantities, and quotations for the dormitory building's power management system are shown in Table 1. Excluding labor costs, the investment is approximately 114,500 yuan.
Table 1. Unit (Yuan)
serial number | Name | model | quantity | unit price | total |
1 | Multifunctional power meter | ACR230ELH | 1 | 3000.00 | 3000.00 |
2 | Three-phase rail-mounted electricity meter | DTSF1352 | 11 | 1000.00 | 11000.00 |
3 | Single-phase rail-mounted electricity meter | DDSF1352 | 108 | 500.00 | 54000.00 |
4 | Communication cables | RVVP2×1.0 | 1000 | 3.30 | 3300.00 |
5 | Serial port server | ACRNET-PORT8 | 1 | 6500.00 | 6500.00 |
6 | Monitoring computer | DELL brand | 1 | 5000.00 | 5000.00 |
7 | printer | HP A4 printer | 1 | 1200.00 | 1200.00 |
8 | Power system software | Acrel-3000 | 1 | 30000.00 | 30000.00 |
9 | Other attachments | Connecting cables, sockets, etc. | 1 | 500.00 | 500.00 |
Total | 114500.00 | ||||
3. Conclusion
In January 2009, the DDSF1352/DTSF1352 single-phase and three-phase electricity meters passed the inspection commissioned by the National Electricity Meter Quality Supervision and Inspection Center (Jiangsu), and all indicators were qualified. In addition to a certain university of science and technology, the products have also been applied in projects such as a cigarette factory in Changsha, a central hospital in Yuncheng, and the 9156 project of a police district in Shanghai, achieving good social benefits.
References
[1] Decree No. 531 of the State Council of the People's Republic of China, Regulations on Energy Conservation in Public Institutions
[2] Ren Zhicheng, Zhou Zhong. Principles and Application Guide of Digital Instruments for Power Measurement [M]. Beijing: China Electric Power Press, 2007.
[3] Shanghai Municipal Commission of Construction and Transportation Notice No. 828 of 2008 on Further Strengthening the Management of Energy-Saving Design Technology for Civil Building Equipment in Shanghai
[4] Su Jian Ke [2007] No. 217, Provisional Regulations on Energy Metering Design for Public Buildings in Jiangsu Province.
About the author:
Zhou Zhong (1968-), male, Bachelor's degree, research focus: low-voltage intelligent power distribution systems. Email: [email protected] Tel: 021-69158302
Li Yili (1959-), male, senior engineer, whose research focuses on the sub-metering of power supply systems in large public buildings.
Wang Xiaoming (1981-), male, Bachelor's degree, research interests include computer system integration. Email: [email protected]
