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Acrel-3000 low-voltage intelligent power distribution system makes full use of the latest developments in modern electronic technology, computer technology, network technology and field bus technology, and conducts distributed data acquisition and centralized monitoring and management of the power distribution system. The secondary equipment of the distribution system is networked. Through the computer and the communication network, the field devices of the decentralized power distribution station are connected into an organic whole, and the remote monitoring and centralized management of the power grid operation is realized.
1. System Structure Description This monitoring system mainly realizes the monitoring and power management of high voltage and low voltage substations in the Taicang Air Conditioning Plant as well as the outdoor dedicated power distribution transformer in Xiqiao. The monitoring range is high and low voltage, and 49 ARKRAY self-manufactured PZ96-E4/C multi-function power meters, 21 third-party comprehensive protection and two temperature controllers are used for remote real-time monitoring and power management. The system 72 only multi-function power meter, divided into 9 bus, the 9 bus through the shielded twisted pair pulled to the serial port server, after data processing uploaded to the duty room monitoring host, to achieve the bus on the meter and monitoring host data connectivity.
The monitoring system adopts a hierarchical distributed structure, namely station control layer, communication layer and bay layer; as shown in Figure (1): .png)
Interval equipment layer is mainly: Ankerui multi-function network power meter, comprehensive protection, temperature controller and so on. These devices are corresponding to the corresponding primary equipment installed in the electrical cabinet, these devices are used RS485 communication interface, through the on-site MODBUS bus network communication, data acquisition on the spot.
The main network communication layer is: serial port server and protocol conversion isolator. Its main function is to convert RS485 signals into RS232 signals or network signals, and complete the data exchange between the field layer and the station control layer.
Station control management: equipped with high-performance industrial computers, monitors, UPS power supplies, printers and other equipment. The monitoring system is installed on the computer to collect and display the operating status of the field equipment and display it to the user in the form of human-computer interaction.
The above network instruments all adopt RS485 interface and MODBUS-RTU communication protocol. RS485 adopts shielded wire transmission. Generally, two wires are used for connection. The connection is simple and convenient. The communication interface is half-duplex communication, that is, both parties can receive and send data. Only data can be sent or received at the same time. The maximum data transmission rate is 10Mbps. The RS485 interface is a combination of balanced drivers and differential receivers. It has enhanced noise immunity and allows up to 32 devices to be connected on the bus. The maximum transmission distance is 1.2 km.
2. Main functions of the power monitoring system 2.1 Data acquisition and processing Data acquisition is the basis of power distribution monitoring. Data acquisition is mainly accomplished by the underlying multi-function network instrumentation, realizing local real-time display of remote data. The signals that need to be collected include: three-phase voltage U, three-phase current I, frequency Hz, power P, power factor COSφ, power Epi, and remote device operating status.
Data processing is mainly to display the electrical parameters collected according to requirements in real time and accurately to the user, so as to meet the requirements of automation and intelligence of the power distribution monitoring. At the same time, the collected data is stored in the database for user query.
2.2 human-computer interaction system provides a simple, easy to use, good user interface. Using the Chinese interface, the CAD graphic shows the electrical main wiring diagram of the low voltage distribution system, shows the status of the distribution system equipment and the corresponding real-time operating parameters, the screen timing switching tour; dynamic refresh of the screen real-time; analog display; switch display; continuous Record display and so on.
2.3 Diachronic History Event The historical event review interface is mainly for the user to view the fault records, signal records, operation records, and limit record that have ever occurred and provide convenient and friendly human-computer interaction. Through the historical event viewing platform, you can according to your own requirements and inquiries. The conditions are convenient for locating the historical events that you want to view, and provide good software support for you to grasp the operation of the entire system.
2.4 Database establishment and inquiry Mainly complete the remote measurement and remote communication quantity collection, and establish a database to generate reports regularly for users to query and print.
2.5 User Rights Management For different levels of users, different permission groups are set to prevent the loss caused by human misoperation to production and life, and realize the safe and reliable operation of the distribution system. You can use user management to perform user login, user logout, password change, and add/delete operations to facilitate the user's modification of accounts and permissions.
2.6 Operation load curve The load trend curve function is mainly responsible for the timing acquisition of incoming line, important loop current and power load parameters, and automatic generation of the operating load trend curve to facilitate the user to understand the operating load status of the equipment in a timely manner. Click the corresponding button or menu item of the screen to complete the switching of the corresponding function; you can view the real-time trend curve or historical trend line; you can perform translation, zoom, range conversion and other operations on the selected curve to help the user to enter the line trend analysis and fault recall. Analyzing the entire system's operating status provides intuitive and convenient software support.
2.7 Remote Report Query The main function of the report management program is to design the report style according to the user's needs. The data processed in the system is filtered, combined and statistically generated to generate the report data required by the user. This program can also be based on the needs of users of the report file to save, print or summon save, print mode. At the same time, this program also provides users with management functions for generated report files.
3. Case Study The monitoring area of ​​Taicang Trane air-conditioning power management system is 1 low-voltage substation, 2 high-voltage substations and 2 special transformers. This project is for the 10/0.4kV power distribution system of this substation. Electric monitoring and power management; monitoring range for remote real-time monitoring and power management of 0.4KV low-voltage loops, 0.4KV low-voltage loops and 10KV high-voltage power distribution loops, low-voltage line cabinets, contact cabinets and feeder cabinets.
The PZ96-E4/C multi-function instrument is used for the in-out line circuit. It is a network power meter designed for the power monitoring needs of power systems, industrial and mining enterprises, public facilities, and intelligent buildings. It can measure all conventional power parameters such as: Three-phase voltage, current, active power, reactive power, power factor, frequency, active power, reactive power and other electrical parameters. And this instrument has 4 photoelectric isolation digital input contacts and 2 relay control output contacts. These contacts can be used with intelligent circuit breakers to achieve remote signaling and remote operation of the circuit breaker. The series of network power meters are mainly used in substation automation, distribution network automation, residential power monitoring, industrial automation, energy management systems and intelligent buildings.
The secondary diagram of low-voltage power distribution is shown in figure (2). The main function of the power telemetry is to monitor the electrical parameters of the operating equipment, including: three-phase voltage, current, power, power factor, electrical energy, frequency and other electrical parameters and distribution loops. Three-phase current; remote signal function to display the operating status of field devices, mainly including: switching of the switch, closing operation status and communication failure alarm; when the circuit breaker is dislocated, it will send an alarm signal to remind the user to deal with the fault in time. 
The remote signaling and telemetry alarm function mainly completes the monitoring of the switching operation status and load incoming line of the low-voltage outlet circuits, and indicates the specific alarm position and audible alarm to the switch displacement and load over-limit pop-up alarm interface, prompting the on-duty personnel to deal with it in time. See Figure (3) and Figure (4). 
The parameter reading function mainly inquires into the electrical parameters of the low-voltage outlet circuit. Supports electrical parameter query at any time, with functions such as data export and report printing. The report queries the electrical parameters for the three substations and the two special variable outlets for each high-low voltage circuit, including: three-phase current, active power and active power, and transformer temperature. The names of the loops in this report are associated with the database to facilitate the user to modify the loop name. See Figure (5). .png)
The electricity consumption report function can select the time period to inquire, supports the accumulated electricity inquiry at any time, and has the functions of data export and report printing. Provide accurate and reliable power report for duty personnel. The names of the loops in this report are associated with the database to facilitate the user to modify the loop name. As shown in the figure below, the precise power consumption of each distribution circuit in a certain period of time, the user can directly print the report, and can be saved to other locations in EXCEL format. See Figure (6). 
The schematic diagram of the system communication structure mainly shows the networking structure of the system. The system adopts a hierarchical distributed structure and simultaneously monitors the communication status of the equipment at the bay level. Green indicates normal communication and red indicates communication failure. See Figure (7). 
The load trend curve interface allows you to visually check the load operation of the loop. View real-time and historical trend curves, click the corresponding button or menu item to complete the switching of corresponding functions; help the user to enter the trend analysis and fault recall, with curve printing function. Provides intuitive and convenient software support for analyzing the health of the entire system. See Figure (8). 
4. Concluding remarks With the development of society and the wide application of electricity, the power monitoring system has become an inevitable choice for large-scale multi-substation users, such as key construction projects, landmark buildings, and large-scale public facilities throughout the country. This article describes the Acrel-3000. The application of the energy management system in Taicang Trane Air Conditioning can realize the real-time monitoring and power management of substation low-voltage power distribution circuits. It not only can display the power status of the circuit, but also has network communication functions, and can be used with serial server and computer. Such as the composition of the power monitoring system, to facilitate the remote management of on-duty personnel in the substation, which will help save energy meter reading time, the information into the distribution monitoring. The system analyzes and processes the collected data, displays the operating status of each distribution circuit in the substation in real time, has a pop-up alarm dialog box and voice prompts for the closing and closing of the load, and generates various energy reports and analysis curves. Graphics, etc., to facilitate remote meter reading and analysis, research. The system is safe, reliable and stable, providing real and reliable basis for users of substations to solve electricity problems and achieving better social benefits. [2]
references:
[1]. Ren Zhicheng, Zhou Zhong, Principles and Application Guide for Digital Power Meters[M]. Beijing. China Electric Power Press. 2007.4
[2]. Zhou Zhongzhong. Smart grid customer end power monitoring and power management system product selection and solution [M]. Beijing. Machinery Industry Press. 2011.10
Design and Application of Taicang Trane Air Conditioning Energy Management System
Overview Taicang Trane air-conditioning project is located at No. 64, Dongting North Road, Taicang City, Suzhou City, Jiangsu Province. This project is Taicang Trane air-conditioning power management system. According to the requirements of power distribution system management, two 10KV high-voltage substations, one 0.4KV low-voltage substation and three special-purpose low-voltage distribution lines are required for power monitoring and power management in Taicang Trane air-conditioning plant. To ensure the safety, reliability and efficiency of electricity use.
Figure (1) Low-voltage network topology
Figure (2) Secondary diagram of low voltage distribution
Figure (3) real-time remote alarm information
Figure (4) Historical telemetry alarm information query
Figure (5) parameter meter reading
Figure (6) Energy Report
Figure (7) System Communication Structure
Graph (8) Trend Graph