Power network user-side power quality online monitoring system scheme
0. Overview
The power grid is composed of five links: "send, transmit, change, match, and use." The user's "combination and use" power link consumes 80% of the total power. With social and economic development, the impact of the electrified railways, electric arc furnaces, frequency converters, and nonlinear, unbalanced loads is increasing in power applications. Power quality problems such as harmonics, negative sequence, flicker, and voltage transients are directly Affects the power supply system security. Electric energy is a commodity, and its quality problem is a common concern of suppliers and customers. Electricity companies need to establish a power quality monitoring system to realize real-time monitoring of the power quality of the entire distribution network.
System composition
The power quality on-line monitoring system mainly includes the on-site monitoring layer, the communication transmission layer and the data management layer. The system topology is shown in Figure 1. There are three modes of networking: network cable, optical fiber, and wireless.
1.1 On-site monitoring layer
Field installation of various types of electrical energy and power quality monitoring equipment requires communication. The main products are ACR330ELH, ACR320ELH, ACR230ELH, ACR220ELH and other power meters. The main functions are shown in Table 1.1.
1.2 Communication Transport Layer
In order to transmit the data collected by the monitoring layer equipment to the server and the data communication transmission equipment, there are mainly communication management machines, serial port servers, and network switches. The data acquisition terminal communicates with the monitoring layer device through the serial port, reads the data therein, performs preliminary analysis, collates, saves the data in a local SD card, and then transmits the data to the wireless communication module. The wireless communication module adopts radio frequency technology to form a wireless local area network on site, collects and transmits data collected by various data collection terminals to a background server, and may also use network cables or optical fibers to transmit data.
1.3 Data Management
The process of storing, analyzing, and applying the collected data includes the installation of servers and the application of various software.
2. System function
2.1 The standard monitoring system has a CAD one-line diagram to show the connection status of the low and middle voltage distribution network; the huge system has the function of multi-screen switching and screen navigation; the distributed power distribution system has the system main screen of the spatial geographic plane. The main screen can directly display the running status of each loop, and has the function of loop charged, uncharged and fault coloring. The main electrical parameters are directly displayed on the human-machine interface and refreshed in real time. A diagram of the monitoring system power distribution is shown in Figure 2.
2.2 User Management
Different levels of users can be given different permissions to ensure the security and reliability of the system during operation. For example, the operator-level user needs to enter the operation password for the opening/closing operation of an important circuit, and the engineer-level user must input the confirmation password to complete the operation.
2.3 Data Acquisition and Processing
Acrel-2000 power monitoring system can be used to collect real-time and time-sequenced parameters and switch status of field devices (including three-phase voltage, current, power, power factor, frequency, harmonics, unbalance, current K factor, and telephone Waveform factor, voltage crest factor, energy, temperature, switch position, equipment operating status, etc.), the collected data can be directly displayed, or a new intuitive data message can be generated by statistical calculation and then displayed (total system power, load maximum , power factor upper and lower limit, etc.), and database storage of important information. See Figure 3.
2.4 Trend Curve Analysis
The system provides two kinds of curve analysis interfaces: real-time curve and historical trend. The current load status of the circuit is analyzed by calling the relevant loop real-time curve interface. For example, by invoking the real-time curve of a given loop, the signal fluctuation caused by the electrical equipment of the loop can be analyzed. The historical trend of the system is that the system can view its historical trend for all stored data, facilitating the quality analysis of the monitored distribution network by the engineering personnel.
2.5 Report Management
The system has a standard power report format and can be designed according to the needs of the user to meet the needs of the report format, the system can automatically design. It can automatically generate various types of real-time running reports, historical reports, event failure and alarm record reports, operation record reports, etc. It can query and print all data values ​​recorded by the system and automatically generate daily, monthly, quarterly and annual reports of electricity. According to the time period of the multi-rate and the set value of the rate, the rate report of energy generation can be generated. The parameters such as the starting point and interval of the query printing can be set by itself. The system design can also be tailored to meet the requirements of different reports.
1. Conclusion
With the development of society and economy and the wide application of power, the management of power quality analysis has become an inevitable choice for the construction of power distribution systems on the user side of the power grid. The power quality analyzer introduced in this paper can realize on-line monitoring of electrical energy and realize the collection of data. Analyze, process, and generate a variety of power and power quality reports, analysis curves, graphics, etc., to facilitate the analysis and research of electrical energy. The product and system are operated in the Olympics temporary power distribution center, Suzhou Jinshu International Apartment and other projects, and have achieved good social and economic benefits.