1. Advantages and Disadvantages of Hierarchical Structure After extensive analysis, it's clear that the communication networks in DCS systems universally adopt a hierarchical structure. This is due to factors like openness, reliability, and real-time data transmission. Different layers handle process data upload, control commands, and more, using various topologies and protocols based on specific needs. The cooperation between these layers forms the overall communication system. Currently, most DCS systems have three main levels: a fieldbus network at the workshop level, a control network between devices, and an operation management network in the control room. Examples include ABB’s PROCONTROLP, Siemens’ TELEPERMXP, Hitachi’s HLACS5000, and Honeywell’s TDC3000. Some systems simplify this by merging the control and operation networks, such as Westinghouse’s OVATION or Foxboro’s I/A. It's important to note that Figure 1 is just a schematic. Each layer can use different topologies like ring, bus, or star. The fieldbus layer connects smart field devices, while the remote bus links remote I/O cabinets. The control network handles communication between controllers and servers, and the operation network connects operator stations and engineering stations. The plant-level information management system (MIS) supports broader functions like production planning and personnel management. However, since MIS usually lacks redundancy and has complex wiring, some experts suggest adding a real-time monitoring network (SIS) between the operation and MIS networks. This ensures efficient communication across units and real-time optimization. Each automation cabinet also has internal communication networks, often using deterministic master-slave or token-based systems. These are not discussed here, but they play a crucial role in system performance. By structuring the network into layers, traffic is isolated, improving both real-time performance and reliability. Faults in one layer don't affect others, and vendors can choose optimal topologies and protocols. For example, using standard Ethernet with TCP/IP enhances openness and reduces costs. High-quality gateways are essential for connecting different networks effectively. 2. Improving Communication Efficiency Through Segmentation Ethernet can become inefficient under heavy load, especially in control layers. Although the operation layer doesn’t require high real-time performance, reducing communication load is still beneficial. Three methods help achieve this: faster Ethernet (like 100 Mbps), switched Ethernet to avoid collisions, and network segmentation. Switched Ethernet is common in systems like MCS’s MAX1000+. Segmentation, however, is particularly effective. By dividing the operation network into two independent segments connected via a bridge, server and network loads are reduced. In case of failure, both segments can work together, ensuring continuous operation. This approach not only improves response speed but also makes better use of resources. Similar techniques are used in control networks, such as in Hitachi’s HIACS3000/5000 and Foxboro’s I/ASeries. Dividing the network by function—like combustion, water supply, or soda systems—reduces communication load and improves real-time performance. Proper network segmentation is key, and placing frequently communicating control cabinets on the same segment significantly boosts efficiency. For example, Hitachi reports that data exchange within the same network takes 200 ms, while across networks it takes 400 ms. This setup allows flexible physical placement of control cabinets, enhancing system design and scalability.
A Main Distribution Frame (MDF) is a signal distribution frame or cable rack used in telephony to interconnect and manage telecommunication wiring between itself and any number of intermediate distribution frames and cabling from the telephony network it supports.
What's more,we can also offer you the MDF Termination Block with good quality and low price.
Distribution Rack, Power Distribution Rack, Distribution Cabinet
NINGBO YULIANG TELECOM MUNICATIONS EQUIPMENT CO.,LTD. , https://www.yltelecom.com