Ethernet in utilities for critical communications networks
by T Craven, H3iSquared
Published in: Transformers and Substations Handbook: 2014
Chapter 3: Substation automation - page 50
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When creating or maintaining a distributed network that services hundreds of devices, it is important to control the traffic. When a shared physical network is being used for everything from corporate accounting to control and automation, the communications network must be correctly planned and configured to ensure communications network control of traffic - that critical traffic is never impeded by non-critical traffic or bottlenecks.
Various mechanisms exist for communications network control of traffic, including VLANs (Virtual Local Area Networks), CoS (Class of Service) and multicast control. The most commonly implemented of these is VLANs, however taking the time and effort to implement all three – Virtual Local Area Networks (VLANs), Class of Service (CoS) and multicast control - will lead to a much more stable and reliable network, especially for critical data exchange.
Virtual Local Area Networks (VLANs) allow us to logically separate devices using the same physical hardware.
The next type of communications control of traffic that can lead to greatly increased stability and decreased latency for critical data is Class of Service (CoS) configurations that tell the switches how to queue the traffic they are sending. There are different Class of Service (CoS) levels available depending on the switch manufacturer (commonly Normal, Medium, High or Critical) and each packet is assigned to one of these levels.
While Ethernet in utilities is able to cater for critical and highly time and latency sensitive data transfers, proper planning and commissioning of the communications network is required. Spending the extra time initially to cater for critical transmissions can lead to a highly stable and reliable communications network in utilities that can be trusted for mission critical control and automation systems.
- When creating or maintaining a distributed network that services hundreds of devices, it is important to control the traffic.
- Virtual Local Area Networks (VLANS), Class of Service (CoS) and multicast control are mechanisms that exist for traffic control.
- Redundancy is an important factor to consider for a critical network.