Introduction Ethernet originated in 1973 when Bob Metcalfe of Xerox sketched its basic outline on a napkin, a drawing still preserved at Xerox's Palo Alto research center. The initial Ethernet standard had a communication rate of 2.94 Mbps. After Xerox collaborated with Intel and Digital Equipment Corporation to develop the DIX 2.0 standard, Ethernet's transmission rate over thick coaxial cable increased to 10 Mbps. Around the same time, the Institute of Electrical and Electronics Engineers (IEEE) designated the CSMA/CD 802.3 standard for Ethernet. The CSMA/CD 802.3 standard was officially finalized and adopted in 1983. In recent years, with the development of computer and network technologies, profound technological changes have occurred in the control field, and Ethernet has gradually entered the industrial sector. Statistics show that currently, over 100 communication protocols are used in the industrial field for data exchange between various industrial computer platforms, from smart sensors to parameter monitoring systems, all utilizing Ethernet. Ethernet is the most common network protocol currently available. Therefore, the development of control system structure towards networking and openness will be the main trend of control system technology development. As the most widely used local area network technology, Ethernet will be increasingly used in industrial automation and process control. II. Introduction to Ethernet Technology and its Development Trend [1] Generally speaking, control system networks can be divided into three layers: information layer, control layer and device layer (sensing/execution layer). Traditional control systems mostly use Ethernet in the information layer, while different fieldbuses or other dedicated networks are generally used in the control layer and device layer. Currently, Ethernet has penetrated into the control layer and device layer, and many PLC and remote I/O suppliers can provide products with Ethernet interfaces that support TCP/IP. Ethernet has brought a storm-like revolution to the automation market for three main reasons: (1) the stimulation of low cost and the improvement of speed; (2) modern enterprises have more and more requirements for real-time production information; (3) the openness and compatibility of Ethernet. In the early Ethernet, multiple nodes shared the same transmission medium, which was called Shared Ethernet. Communication between nodes was done by broadcasting, which was prone to conflict. Shared Ethernet uses CSMA/CD technology to avoid collisions. When a collision is detected, the sender pauses transmission, delays randomly for a period, and then retransmits until successful. Because the delay is random and cannot be known in advance, the time response of shared Ethernet is uncertain and cannot be used in high real-time applications. Switched Ethernet overcomes this shortcoming. An Ethernet switch is a multi-port bridge at the data link layer (Layer 2 of the ISO/OSI reference model), which can also be considered an intelligent distributor. The switch divides the network it manages into many physically isolated but logically interconnected nodes in a star topology. Each node establishes a physical connection with the switch individually. During communication, the switch establishes a dedicated full-duplex channel between the sending and receiving ports, which has the full bandwidth of the Ethernet and avoids collisions. Switched Ethernet achieves determinism while significantly increasing transmission speed. Gigabit Ethernet is already widespread, and 10Gb/s switched Ethernet is under development. When Ethernet is used for information technology, the application layer includes HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), SMTP (Simple Email Transfer Protocol), and Telnet (remote login). These TCP/IP-based protocol suites have become the de facto network standard in industry, playing a crucial role in interconnecting different network systems from different manufacturers. However, when Ethernet is used for industrial control, its application layer manifests as real-time communication, objects used for system configuration, and application protocols for engineering models. The development of Industrial Ethernet and Internet technologies will completely change the network architecture of traditional industrial enterprises. Industrial Ethernet has extended from the information layer down to the control and device layers. With the adoption of Ethernet architecture, the location of controllers can break through the limitations of traditional network architectures, and can be located in the field or in the central control room. Currently, controllers and even remote I/O support Ethernet functionality more and more strongly. Some controllers and remote I/O modules have integrated web servers, allowing users at the information layer to directly obtain the current status values ​​of controllers and remote I/O modules, just like users at the control layer. Manufacturing enterprises that adopt Ethernet architecture and open software systems are also known as "transparent factories." In addition, real-time remote monitoring of industrial production processes can be achieved through the Internet, combining real-time production data with ERP systems and real-time user needs, making production not just order-oriented but "electronic manufacturing" directly oriented towards opportunities and markets, thus enabling enterprises to adapt to the requirements of economic globalization. Many industrial control systems are committed to developing IP and Ethernet technologies. The rapidly developing information technology has become part of the industrial control network. The current development status of Ethernet technology is shown in Table 1. Table 1 Development status of Ethernet technology III. Serial port Internet access technology [2] In the process of system networking, since many traditional serial port devices do not have networking capabilities, there must be a serial communication to TCP/IP network solution for the transmission of control commands and device information [4]. Serial communication network technology is simple, easy to use, and cost-effective, making it an ideal choice for system networking. MOXA's Nport series serial port Internet access servers have now appeared on the market. Using MOXA's standard serial port driver, MOXA's serial port can be simulated as a remote COM port without changing the original application software or communication components that use serial communication. The advantage is that with the support of Windows and Linux/Unix drivers, the Nport family can immediately enable serial port devices to have networking capabilities. The Nport family device Internet access server contains a complete TCP/IP protocol. It can package serial port data into TCP packets and convert them into frames that can be transmitted over Ethernet, and transmit them to the host's Ethernet card. After the host decapsulates the packet using its own TCP/IP protocol, the application can receive the complete serial port data. Serial port data is accessed via TCP/IP sockets, not drivers, through the Nport family of TCP ports. This solution is suitable for all systems with TCP/IP connectivity. Enabling serial devices with a TCP/IP network interface improves enterprise management and operational efficiency. The remote and mobile management capabilities of TCP/IP networks significantly reduce system failure maintenance and manpower costs, making it a cost-effective serial device management model. IV. Ethernet-based SCADA System Modern automated management of oil pipelines often adopts SCADA systems (Distributed Data Acquisition and Monitoring Systems). In domestic and international oil pipeline design, SCADA systems have become an indispensable choice and a standardized facility for pipeline system management and control. Metering stations, pressure regulating stations, pigging stations, cathodic protection stations, etc., are all remotely measured and controlled by SCADA systems. 1. Basic Configuration of SCADA System 1.1 Central Control Level (Control Center) The dispatch control center is the central hub of the SCADA system, continuously monitoring and managing the pipeline. The system should ensure the integrity, timeliness, accuracy, security, and reliability of data acquisition and storage. Simultaneously, the system should be open, supporting user development, supplementation, and improvement of application functions. The computer system of the dispatch control center is generally configured as a client/server architecture, using a real-time task operating system, with hot standby redundancy for the server and local area network. This control center is equipped with operator workstations, engineer workstations, manager terminal stations, a large-screen projection system, routers (redundant configuration), modems, etc. 1.2 Station Control Level (Station Control System) The station control system is the remote monitoring station of the SCADA system, the foundation for ensuring the normal operation of the SCADA system, and is set up in control rooms in various locations. The station control system mainly consists of process control units, operator workstations, and data communication interfaces. The process control units use high-performance, high-reliability programmable logic controllers (PLCs) and I/O framework connection networks. The operator workstations, serving as human-machine interfaces, use industrial-grade workstation computers. The station control system hardware configuration includes: PLC, operator workstations, laser printers, routers, operator consoles, etc. 1.3 System Synchronization To ensure the consistency of data across all parts of the SCADA system, maintaining system synchronization is crucial. Firstly, a GPS clock is set as the standard time for the entire system at the dispatch control center, and the hardware clock error of each station control system is required to be no more than 1 second. System clock synchronization is performed by sending a clock check to each field station from the front-end unit; a check is mandatory when the RTU restarts; and a check should be performed when interrupted communication is restored. System Grounding and Protection. The automatic control system uses equipotential bonding for grounding. All operating stations, consoles, and cabinets in each station control room should be protected by grounding, connected to the electrical safety grounding network. The grounding terminals of instrument signal circuits and shielding grounding terminals are connected to the signal grounding network. The resistance of both protective grounding and signal grounding is less than 4Ω, and the signal grounding network and the electrical safety grounding network are connected to the potential grounding electrode respectively. 2 Hardware Composition of the SCADA System The main components of the SCADA system are PLC and DCS [sup][4]. [/sup] The SCADA system is a small-to-medium-scale measurement and control system. It integrates the advantages of the PLC's strong field measurement and control functions and the DCS's strong networking and communication capabilities, offering a high performance-price ratio. 3. New Generation Ethernet SCADA System [sup][5][/sup] With the profound changes in computer and communication technologies, the means of implementing monitoring systems in large-scale oil pipeline projects will inevitably undergo fundamental changes. Traditional SCADA systems based on the CDT/POLLING protocol are insufficient to meet the monitoring requirements of large-scale gas transmission networks. The connections between various systems in oil transmission projects (such as oil transmission dispatch and monitoring systems) are becoming increasingly close, necessitating unified consideration. Therefore, a large-scale system based on Ethernet (LAN, MAN, WAN) for the entire oil transmission system is proposed. SCADA functionality is integrated through computer software platforms (UNIX, Linux, Windows, Java, etc.). First, fiber optic cables need to be laid from local distribution stations to the dispatch center. The basic idea is to construct a high-speed network with gigabit fiber optic Ethernet as the backbone and 100 Mbps fiber optic cables as subnets or branches, using routers, fiber optic network switches, and fiber optic cables. The Inter-Control Center Communication Protocol (ICCP) enables an oil pipeline control center to exchange data with other oil pipeline control centers within the same enterprise, other oil pipeline companies, joint ventures, regional control centers, and independent adopters via a Wide Area Network (WAN). The exchanged information consists of real-time and historical data for monitoring and controlling the oil pipeline system, including measurement data, planning data, oil volume settlement data, and operational information. Data exchange between the control center's SCADA host and other control center hosts typically involves one or more intervening communication processors. The control center model includes several basic host processors: SCADA, load management, distributed applications, and display processors. In a SCADA system, the SCADA host is the primary processor, collecting and processing analog and digital signals to monitor data through Data Acquisition Units (DAUS) and Remote Terminal Units (RTUS). Control centers typically have redundant SCADA hosts in a "hot standby" state. Distributed application hosts perform various complex analysis and scheduling plans. Display processors facilitate the display of data flow and control information for operators. The control center usually connects these hosts through one or more local area networks (LANs) and often accesses various wide area networks through an intermediate communication processor. V. Summary From the above discussion, we can draw the following simple conclusions: the development trend of petrochemical automation should be distributed, open and information-based. The distributed structure is a network that can ensure that each intelligent module in the network can work independently, achieving the concept of system risk dispersion; openness means that the system structure has an interface with the outside world, realizing the connection between the system and the external network; information-based means that the system information can be comprehensively processed, and combined with network technology to realize network automation and integrated management and control. Automation based on Ethernet technology has low cost and openness, can realize remote control, is easy to combine with management, and realize integrated management and control. References: [1] Yao Xilu. Fieldbus Control Technology. [M]. Higher Education Press, 2006. 156～168 [2] Lu Demin, Zhang Zhenji, Huang Buyu. Petrochemical Automation Control Design Manual. [M]. Chemical Industry Press. 2002 [3] Zhang Lechang. Implementation of SCADA System for Natural Gas Pipeline. Natural Gas and Petroleum, 2001, (1): 36-37 [4] Xu Furong. Characteristics and differences of the three major control systems: PLC, DCS and FCS. [R]. China Industrial Control Network. [5] Qi Shouzhi. A new generation of SCADA system based on fiber optic Ethernet. Automation Equipment, 2001, (7): 49-52