Industrial Ethernet has very rapidly become the reliable technology for Automation Communication within production plants, Utility Substations and ITS environments. Some of the reasons for this rapid change is based on flexibility, expandability, reliability, resilience, open world standard protocols, ability to adopt legacy protocols, ease of troubleshooting and maintenance and minimized cabling requirements.
Most Programmable Logic Controllers (PLC) and Remote Terminal Units (RTU) vendors are now making their equipment with Ethernet interfaces forcing the migration to Ethernet based systems. It is now possible to activate a PLC/RTU in the field and have visual confirmation (for safety purposes) over existing infrastructure such as : fiber, Satellite, GSM , Wifi or WiMAX options- remotely!
Ethernet typically uses a standard Unshielded Twisted Pair Cable (UTP) with a category rating based on the performance required. The cable is fairly inexpensive but has a distance limitation to 100m (This is without any interfering factors). When a connection is required further than 100m then you would look at the following options to extend the connection required:
- Switch to repeat the signal and propagate it a further 100m (This is a limited option)
- Convert the UTP Cable to a Fiber Cable through the use of a media converter
- Fiber to be used is Multimode or Singlemode
- The selection of fiber is based on the distance and the speeds you require from your system
- Wireless
- This is typically used in applications that don’t have a high data throughput and is prone to be less reliable than UTP or Fiber
- Wireless can be used from a few meters to a few Km’s, this is based on if you are using un/licensed frequencies which in turn will dictate if you should have line of site communication or not.
When most plants started with Ethernet, correct planning for future vision was not always kept in mind with regards to considerations of expansions of the plant/site, future implementation of additional PLC’s, RTU’s, IP Camera’s, VoIP, Fire Detection and many more peripherals. Such expansion would have an impact on the original design for IP Structures and design layouts. Thus your initial design and choice of equipment will be a large factor in how the expansions would be dealt with.
The equipment to use for the communication backbone in Automation Systems is critical since majority of the automation process is reliant on reliable communication. It is critical since failure of equipment or design will impact production and potentially be a safety hazard!
The reality is if you have an existing plant it is not a financially feasible option to replace all older PLC’s/RTU’s to the new age style with Ethernet Ports embedded.
In such a case, use of a Serial Device Server would be required in order to convert existing RS232/422/485 Serial communication to Ethernet.
There are two methods for making use of these converters:
The second method minimizes the requirement for additional converter hardware.
How to manage your Ethernet Network:
In order to manage an Ethernet Network effectively, you would require to have all your Ethernet Switches/Routers enabled for Simple Network Management Protocol (SNMP) and if possible to have the end devices also configured with this standard protocol.
A network management station is an intelligent piece of software that communicates via SNMP to all managed devices on the network to gain information regarding their state of operation and their health status thus assisting to be proactive rather than reactive to any potential maintenance required on the network.
If a problem occurs, the system will automatically notify the relevant person on shift with an email or sms regarding the state of the network and condition of the notification.
Training on such a system is an essential part to a successful deployment and reliable communication with maximizing safety!