0 Introduction
Grid dispatch automation is based on the early power system remote control system, the introduction of computer technology and functional expansion to form a set of automated systems to assist dispatchers to work, the remote control system is an important part of the grid dispatch automation system, in The development process of the power grid dispatching automation system plays a fundamental role. The telecontrol system refers to a system that monitors and controls the production process in a wide area. It includes all functions and equipment for collecting, processing, transmitting, displaying, and executing necessary process information. Real-time transmission of dispatching information of telecontrol system is very important to ensure the orderly completion of dispatching tasks of power system.
This paper mainly researches and discusses the power system dispatching information transmission system based on embedded Ethernet, and hopes to find an effective design method for the power system dispatching and communication real-time transmission system that can be used as a guide or for reference. share it.
1 Overview of the application of Ethernet technology in power dispatching systems
The development of electric power information transmission system must meet the development requirements of power grid dispatch automation and the requirements of telecontrol system to network development. The future development trend of electric power information transmission system must be networked. This thesis focuses on the application of embedded Ethernet communication technology in power information transmission.
With the application of computer network technology in power systems, dispatch centers generally use local area networks, and more often use local area networks configured on Ethernet. In the SCADA system based on LAN, it is generally necessary to configure front-end workstations, dispatching workstations, and remote control workstations. In addition, some microcomputer workstations can also be added to the LAN, such as the office of the director and the chief engineer, mainly used to monitor the power grid. Real-time running status, displaying real-time pictures, providing alarm information, etc.
The application of Ethernet technology in the plant station is mainly in the substation integrated automation system. The substation integrated automation system has developed into a typical hierarchical distributed structure driven by communication technology. The structure is generally divided into 3 layers: substation layer, partition layer and process layer. Among them, the process layer contains the production process facilities in the substation, such as transformers, circuit breakers and their auxiliary contacts, current and voltage transformers, etc., which is mainly responsible for on-site data collection, providing I / O interfaces, etc .; the bay layer contains measurement and control units, Responsible for the parameter measurement and monitoring of the unit line or transformer and the control of the circuit breaker. The substation layer contains a full-station monitoring host, communication and control host, and an engineering station that implements management and other functions. With the development of computer technology and communication technology, especially the application of network technology, Ethernet technology is being introduced into the process layer acquisition, measurement unit and bay layer protection and control unit of the substation automation system, thereby forming a distributed network-based control Substation automation system.
2 Application research of embedded Ethernet in power dispatch communication system
2.1 Basic requirements of power dispatch communication system
Compared with other information transmission, the transmission of electric power information has its particularity, mainly expressed in the following points:
(1) Compared with general Ethernet applications, the amount of data transmitted by power information is not large, and there is usually no large data file transmission.
(2) High reliability requirements. Power information requires accurate and reliable transmission.
(3) High real-time requirements. The substation automation system requires timely transmission of real-time operation information and operation control information on site. The network must be able to ensure the real-time performance of data communication.
(4) High anti-jamming capability requirements. The communication environment in the substation is bad, and the mechanical and electromagnetic interference are serious. The network must have good anti-interference ability.
2.2 Application mode selection of Ethernet
The application of embedded Ethernet technology to the substation automation system can realize the transmission of the RTU information of the plant station to each master station through the network. There are two specific ways: First, the network interface communication mode. This mode requires that the RTU of the factory station has an Ethernet interface, supports TCP / IP protocol, and supports the IEC 60870-5-10 or IEC 61850 protocol, directly accessing the LAN port of the edge switch of the data network at the factory station. This mode is suitable for the distributed automation system of new plant stations. Second, the protocol converter mode. For most of the factory stations that have been put into operation, a TCP / IP protocol converter can be installed on the RTU and then connected to the SPDnet, so that the original communication protocol and the structure of the RTU remain unchanged. TCPP / IP protocol network communication front-end system and corresponding application layer protocol.
There are two typical application modes for embedded Ethernet in the substation internal communication network:
Application mode a: Each bay device is equipped with an embedded Ethernet interface, which is directly connected to the Ethernet as a node.
Application mode b: Several intelligent electronic devices (IED) without an Ethernet interface are connected together by means of RS-232 / 485 or field bus, etc., and then connected to a communication management unit with an Ethernet interface, which is managed by the communication The unit is connected to the Ethernet.
In terms of technical implementation, both must design an embedded Ethernet interface, which is essentially not much different.
2.3 Ethernet communication module design
The Ethernet communication module designed in this thesis is an embedded Ethernet interface hardware circuit based on a software protocol stack. This circuit uses the STC89CS16RD + single-chip microcomputer of Hongjing Company as the embedded microprocessor, and externally connects to the RTL8019AS Ethernet controller chip to form a basic hardware platform.
The Ethernet controller chip RTL8019AS, its working clock is 20MHz, the AEN pin is grounded, and the address is always in effect.
The IOCS16 pin is pulled down to ground with a resistor, and the reset time is low, and the 8-bit mode is selected (the network card is compatible with 8-bit and 16-bit operation. Because the STC89C516RD + 8-bit data bus requires the 8-bit bus mode of the network card). The IORB and IOWB pins are connected to the RD and WR pins of the single-chip microcomputer, respectively.
The connection of the address line is SA19-SA10 ground, SA9 connects to high level, SA8-SA7 connects to ground, SA6 connects to address line A15, SA5 connects to ground, SA4-SA0 connects to address line A12-A8. The connection of the data line is: SD0-SD7 is connected to the P0 port of the single chip microcomputer. Connect 65 pin JP to high level and set RTL8019AS to jumper mode. The reset pin RSTDRV is connected to the reset pin RST of the microcontroller. When the microcontroller is reset, the network card is also reset. There are two types of reset methods for RTL8019AS: cold and hot. RSTDRV is the reset pin of RTL8019AS. Apply a high level of more than 1μs to this pin to achieve cold reset; read and then write to the reset port to achieve warm reset. Because the reset process will perform some operations, you should wait for 100ms before operating the RTL19AS to ensure that the reset is complete.
2.4 Real-time collection and transmission mechanism of system data
The client communicates with the serial port of the remote control device (RTU) through the bus RS-485 or RS-232 communication adapter, and controls the work of each remote control device (RTU). Therefore, the most important thing is to realize the remote control device (RTU). ) Data collection. This system software uses query to process information. Using DELPHI 7.0 as a development tool and using communication controls to edit communication programs, the key is to accurately understand and set the properties of the communication controls.
In order to realize the sharing of telemetry and telesignal data of the remote control system of the power system and avoid conflicts caused when two threads access the same data, the synchronization technology provided by Windows API can be used to synchronize the simultaneous access of multiple threads to the same data class. Mutex (mutually exclusive object) is a global object that serially accesses resources. You can set the mutex object first, then access the resource, and finally release the mutex object. While setting the mutex, if another thread (or process) tries to set the same mutex, it will stop until the previous thread (or process) releases the mutex.
In the process of remote data transmission, the client should always detect the line connection with the dispatch center server. When the network is abnormal, such as disconnection, the client will give the monitoring system fault information, and automatically restart the data after the fault is restored. Transmission, this is very important in the monitoring system.
3 Conclusion
With the continuous expansion of modern power system scale, the system structure and operation mode are becoming more and more complex, any small mistake may have fatal consequences for the entire power grid, so the development of power dispatching communication system is increasingly urgent, and the use of embedded Ethernet technology It can be applied to the power telecontrol dispatching communication system, which can improve the anti-interference of the power system information transmission while ensuring the real-time information transmission. As the command center of regional power grid operation management, the power grid dispatching center has the reliability, flexibility and intelligence of the dispatch automation system used to ensure the safe, high-quality and economical operation of the entire power grid.
12v din rail power supply have 36W and 60W, output current 3A and 5A.
Features:
Wide input range: 100-240V, 50/60Hz.
Easy for the installation and can move in the rail follow CCTV when working
Cooling by free air convection
LED indicator for power on
Protection: short circuit, over current, overload, over voltage.
Efficiency 85%
100% full load burn-in test
3 years warranty
Product application:
Suitable for home automation, CCTV, security camera and led lighting
Din-Rail Power Supply,Din-Rail Power Supply 12Vdc,Din Rail Power Supply Applications,Din Rail Power Supply 48Vdc
Guangdong Steady Technology Co.LTD , https://www.steadysmps.com