Learn how to plan, select, configure, and test a PLC network for a large-scale plant using different network topologies, architectures, and protocols.

While designing PLC network of a large network following things to be considered :- 1) Topology - Star or Ring , In case of Rockwell PLC having remote nodes , ring is mostly preferred by using multi mode fibre using ETAP . 2) In case there are multiple standalone PLC’s assigned to substations , make sure to keep the same ip series and sub net mask , this will help in future when you will create data pipeline for analytics otherwise you will have to do NAT in future. 3) In case multiple PLC vendors are involved as standalone systems, use same ip series but dont conflict the ip address . Try to bring a fiber core from all substations to a L3 device (vlan) for future integration in case you want to make data pipelines .

How can you design a PLC network for a large-scale plant?

A PLC network is a system of interconnected PLCs that communicate and exchange data to control and monitor a large-scale plant. PLCs are programmable logic controllers that can execute logic, sequencing, timing, counting, and arithmetic operations for industrial automation. Designing a PLC network for a large-scale plant requires careful planning, selection, configuration, and testing of the network components and protocols. In this article, you will learn how to design a PLC network for a large-scale plant in six steps.

1 Define the network requirements

The first step is to define the network requirements based on the plant layout, processes, functions, and performance. You need to identify the number, location, and type of PLCs and other devices that will be connected to the network, such as sensors, actuators, human-machine interfaces, and servers. You also need to determine the data flow, bandwidth, latency, reliability, and security needs of the network. The network requirements will help you choose the most suitable network topology, architecture, and protocol for your PLC network.

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Alex Cherpakov, Ph.D.

Sr. System Architect at Rockwell Automation
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Unfortunately, there is not enough information in the question to even start to provide recommendations. 1. Large scale as how many nodes? 2. Shop type or distributed location? 3. Discrete, process, hybrid? 4. PLC2PLC network? PLC2IO? PLC2HMI? PLC2Cloud? Typical system/shop has at least 2 networks (usually 3) 5. Performance expectation in tags/sec? 6. "greenfield" or "brownfield"? 7. Noise level (can use wireless)? Etc., etc., etc.

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2 Choose the network topology

The network topology is the physical arrangement of the network components and the connections between them. There are different types of network topologies, such as star, ring, bus, tree, and mesh. Each topology has its own advantages and disadvantages in terms of cost, scalability, redundancy, and maintenance. You need to choose the network topology that best meets your network requirements and plant layout. For example, a star topology is simple and easy to expand, but it requires more cables and a central hub that can be a single point of failure. A ring topology is reliable and fault-tolerant, but it has lower bandwidth and higher latency than a star topology.

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3 Choose the network architecture

The network architecture is the logical organization of the network components and the communication rules between them. There are different types of network architectures, such as master-slave, peer-to-peer, client-server, and distributed. Each architecture has its own advantages and disadvantages in terms of data exchange, control, and flexibility. You need to choose the network architecture that best meets your network requirements and functions. For example, a master-slave architecture is simple and centralized, but it relies on a master device that can be a bottleneck or a single point of failure. A peer-to-peer architecture is decentralized and cooperative, but it requires more coordination and synchronization between the devices.

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Ashutosh Mantry

Assistant General Manager- Automation & Digitization | Industry 4.0 and Digital Transformation Enthusiast | PTC certified kepware associate
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While designing PLC network of a large network following things to be considered :- 1) Topology - Star or Ring , In case of Rockwell PLC having remote nodes , ring is mostly preferred by using multi mode fibre using ETAP . 2) In case there are multiple standalone PLC’s assigned to substations , make sure to keep the same ip series and sub net mask , this will help in future when you will create data pipeline for analytics otherwise you will have to do NAT in future. 3) In case multiple PLC vendors are involved as standalone systems, use same ip series but dont conflict the ip address . Try to bring a fiber core from all substations to a L3 device (vlan) for future integration in case you want to make data pipelines .

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4 Choose the network protocol

The network protocol is the set of rules and standards that govern the communication and data exchange between the network components. There are different types of network protocols, such as Ethernet, Modbus, Profibus, Profinet, and EtherCAT. Each protocol has its own advantages and disadvantages in terms of speed, compatibility, and functionality. You need to choose the network protocol that best meets your network requirements and performance. For example, Ethernet is a common and widely supported protocol that offers high speed and flexibility, but it requires more hardware and software components and configuration than other protocols. Modbus is a simple and robust protocol that offers easy integration and compatibility, but it has lower speed and functionality than Ethernet.

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5 Configure the network components

The next step is to configure the network components according to the chosen network topology, architecture, and protocol. You need to assign the network addresses, parameters, and settings for each PLC and other device that will be connected to the network. You also need to program the logic and functions for each PLC and device that will be involved in the control and monitoring of the plant. You can use various software tools and methods to configure the network components, such as graphical user interfaces, ladder logic, function block diagrams, and structured text.

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6 Test the network performance

The final step is to test the network performance to ensure that the network components communicate and exchange data correctly and reliably. You need to verify that the network meets the network requirements and functions that you defined in the first step. You also need to check that the network is secure and resilient to faults, errors, and disturbances. You can use various tools and methods to test the network performance, such as simulation, debugging, monitoring, and troubleshooting.

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7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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Krishna Ragothaman

Manager/Projects/ UTKAL Alumina International ltd/HIL/ABG
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My view, For a large Scale industry, mostly continuous process operation DCS is preferred. 1 Integrated Solution. If Batch Process is there, we can consider PLC, for its optimised and fast process operation. Before selecting any control system, Process Application is mandatory.

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Krishna Ragothaman

Manager/Projects/ UTKAL Alumina International ltd/HIL/ABG
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My view, For a large Scale industry, mostly continuous process operation DCS is preferred. 1 Integrated Solution. If Batch Process is there, we can consider PLC, for its optimised and fast process operation. Before selecting any control system, Process Application is mandatory.

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Himansu kar

10+ year Experienced Energy Professional with Expertise in Project Planning, Execution, and Management
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Design a PLC (Programmable Logic Controller) network for a large-scale plant by first identifying all control points and their communication requirements. Utilize a hierarchical architecture, employing industrial Ethernet or fieldbus protocols for communication between PLCs and I/O modules. Implement redundant communication paths for reliability. Employ managed switches for network segmentation and prioritization. Regularly update and maintain the network for optimal performance and security.

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How can you design a PLC network for a large-scale plant?

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1 Define the network requirements

2 Choose the network topology

3 Choose the network architecture

4 Choose the network protocol

5 Configure the network components

6 Test the network performance

7 Here’s what else to consider

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