Keywords: electric energy management system, electric energy meter, guide rail installation, RS485 communication
1 Foreword In response to a series of policies and measures formulated by the State Council to promote energy conservation and emission reduction, various industries across the country have actively taken measures to save energy and save energy, and have made positive progress. However, whether the implementation of the power-saving program and the widespread use of power-saving equipment have really played a role in saving energy, we must use a reasonable assessment management mechanism to make a scientific judgment.
A company's factory building has one power distribution room in the first phase and two power distribution rooms in the second phase, providing production, lighting, air conditioning power and other power for the whole plant. The original power distribution system was only equipped with the power department's electricity meter on the total incoming circuit of the whole plant. The manager can only know from the total amount of electricity provided by the power department each month that the power consumption of this month is used. Where is it, is there any waste of electrical energy, and whether energy-saving measures have received the expected results, enterprise managers are not very clear. A reasonable electric energy assessment mechanism is urgently needed to realize the scientific management of electric energy.
In response to the above problems, and according to customer requirements, the original power distribution system has been transformed. The modified Acrel-3000 power management system can not only realize remote monitoring and centralized management of each distribution circuit, but also achieve The monitoring equipment performs classified energy statistics, double-rate energy statistics, 8-hour team energy consumption statistics, daily energy consumption statistics, and monthly energy consumption statistics, and automatically calculates the energy consumption per unit output, which provides a basis for scientific energy-saving management.
2 Project analysis The electric energy management system is to add an electric energy meter with a communication interface on the basis of the original substation and distribution cabinet, and transmit the electric energy parameters to the monitoring center, so as to realize a centralized remote monitoring and management of a low-voltage distribution transformation project.
To realize the statistics of power consumption of each machine and the collection of energy data of each outlet circuit, an energy meter must be installed in each outlet circuit, but the current electricity meter on the market generally uses the traditional wall-mounted type The installation method is bulky and inconvenient to install. The power distribution cabinets of the company's original power distribution system are all drawer cabinets. Ammeters and signal indicators have been installed on the original drawer cabinet panels. The installation space is very narrow. It is impossible to add any traditional energy meters to the drawer panels. The components installed inside the drawer are very close, and it is impossible to install traditional electric energy meters or digital power network instruments.
What if the measurement circuit is led out from each loop transformer, a new meter box is rebuilt and placed next to the power distribution cabinet, and the energy meter is installed in the meter box? This method will cause a lot of cables from the meter box to the distribution cabinet. In view of the large number of distribution circuits in the company's plant, the installation and wiring are more troublesome, and later maintenance and repair will be more difficult. Adding so many cable lines and The newly added meter box will also increase the economic cost of users, so this method is not desirable.
Considering various factors such as instrument installation, commissioning and post-maintenance, the ADL series rail-mounted energy meter was finally selected. This series of instruments can be easily installed on the guide rails on the back of the power distribution cabinet, without the need to re-open the power distribution cabinet, and there is no need to lead a large number of cables into the new meter box, which is convenient to install and saves a lot of cables and meters The cost of the box, and this one-to-one measurement, is also very clear and convenient for future system maintenance.
ADL series rail type electric energy meters all have standard RS485 communication interface, adopt Modbus RTU international standard communication protocol, network the meters through the communication interface of the meters, and finally realize centralized monitoring and management in the monitoring center.
3 ADL rail mounted energy meter
ADL series rail-mounted energy meters include single-phase double-rate electric energy meters and three-phase double-rate electric energy meters. This series of electric energy meters are small in size, beautiful in appearance, modular in structure, and can be installed on 35mm standard rails. Figure 1 shows the appearance and installation of ADL series instruments.
Figure 1 ADL series appearance and installation method
ADL series rail-mounted electric energy meter supports two connection modes: one access and two access. It can be used not only in low-voltage distribution cabinets, but also in terminal distribution boxes. The maximum specification of the ammeter is 20 (80) A.
ADL series rail-mounted energy meters not only have flexible and convenient features in appearance and wiring, but also have the following advantages in function and performance:
a. Measure the positive and negative active power, the power flow direction is automatically identified and indicated, and it has the function of 4 rates and total energy measurement.
b. The rate-sharing function can be divided into 4 rates and 8 periods in a daily period. The minimum time unit within the period is 1min.
c. Monthly freeze transfer function can count the total power consumption and time-sharing power consumption of the previous month, last month and this month, used for the settlement of monthly electricity charges and monitoring of electricity consumption.
d. Real-time monitoring function, measuring and displaying voltage, current, frequency, power, power factor.
e. Output interface. Power pulse data output interface with photoelectric isolation can be used for meter calibration and remote transmission of DCS (Distributed Control System), RS485 communication interface can realize remote meter reading and load monitoring.
4 System composition The electric energy management transformation system adopts the layered distributed computer network structure, namely the interval layer, communication layer and station control layer, as shown in Figure 2.
Figure 2 Schematic diagram of the power management system
Shielded twisted pair is used for bus-type connection between the instruments, and the monitoring host is entered through the communication expansion card. Figure 3 shows the schematic diagram of ADL instrument communication cable wiring. By networking the secondary devices of the power distribution system and reaching the monitoring host via the communication network, the field devices of the distributed power distribution station are connected as a whole.
Figure 3 ADL instrument communication cable wiring diagram
The monitoring center is equipped with monitoring computers, printers, UPS power supplies and necessary auxiliary equipment. Acrel-3000 energy management software completes the remote collection and centralized processing of each energy meter.
5 Software implementation and system functions
5. 1 software implementation The host computer software uses Acrel-3000 configuration software, through the software for device configuration, database variable configuration, interface design, etc., to complete the functions of the host computer software monitoring and power management.
5. 2 System functions The entire system realizes the collection and statistics of all loop electrical energy in the first-phase distribution room and the second-phase distribution room, remote automatic meter reading, electrical energy statistics and other functions, including:
a. Remote power parameter measurement, including real-time power, distributed power, total power, and statistical power according to each monitoring device.
b. Running state monitoring, alarm notification of abnormal communication.
c. User management, different user rights have different operation functions, and all levels of rights have password modification operation functions and authorization error prevention functions.
d. Electric energy report, which realizes the query of all electric energy reports according to time, which is divided into five types: minutes, hours, shifts, days, and months, including total, sharp, peak, flat, and valley rate electricity and power consumption.
e. Energy histogram, real-time energy histogram display of any loop energy, including total, sharp, peak, flat and valley energy.
f. Summary table, the energy of all monitoring equipment is summarized, inquired according to the time period, and the power consumption at any time is automatically calculated.
g. Unit energy consumption, automatically calculate the energy consumption per unit output, and print and export. The calculation interface of energy consumption per unit output is shown in Figure 4.
h. Print and export, all reports and interfaces can be printed or exported in EXCEL, WORD format.
Figure 4 Single-chip energy consumption report
6 Concluding remarks The system has been debugged and accepted, and has been successfully put into operation. The system software screen refresh time is less than 1s, the accuracy of remote signal processing is greater than 99.9%, and the entire system is safe and stable, which greatly facilitates the use of users.
The application of ADL rail type electric energy meter is of practical significance for accurately measuring electric energy, saving installation space and saving engineering cost. Compared with the traditional wall-mounted electric energy meter, its small size, simple appearance, flexible wiring method, convenient installation, and energy The simplification and centralization of the management system provides convenience.
The system calculates each monitoring device completely according to the customer's requirements, calculates the energy allocation number of the common device and the energy consumption per unit output, and makes four types of reports: minutes, hours, days, and months. The convenient energy database report greatly reduces the user's investment in energy meter reading manpower, provides an intuitive basis for managers to conduct internal measurement assessment, and lays the foundation for further energy-saving management and energy-saving measures.
The article comes from: "Building Electric" 2010, Issue 2.
1 Ren Zhicheng, Zhou Zhong. Principles and Application Guide of Electric Power Measurement Digital Instruments. Beijing. China Electric Power Press, 2007:
About the Author:
Yu Jing, female, undergraduate, engineer of Wuhan Ankerui Electric Co., Ltd., the main research direction is intelligent power monitoring and power management system
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