Monitoring for Water and Sewage
Challenge
Remotely communicate PLCs spread across several units of the Water and Sewage system of a large Brazilian city.
Solution
Multiplexing of Serial PLCs over the Internet via a virtual Serial channel.
The client's request was to control and telemetry several points in the water supply and sewage system of a large Brazilian city. The high cost of acquiring and maintaining dedicated lines (LPs) made it highly expensive to perform these tasks reliably and continuously. The Operational Control Center, located at the customer's headquarters, needed permanent communication with the PLCs located at these points.
Project requirements:
- Reliable and stable communication with PLCs spread across the city, many in difficult-to-access areas;
- Affordable cost of the solution;
- Possibility of connection via Ethernet or Serial on the same equipment, for standardization and integration with different PLC models.
Several technologies were tested and each demonstrated weaknesses, such as low robustness or communication instability. LPs, for example, often had wires stolen. Communication solutions via wireless networks were unfeasible due to reasons of sight and distance. Satellite communication, in turn, had a very high operating cost.
In addition to these difficulties, there was also a complicating factor: the multiplexing of serial networks for PLCs to communicate via the cellular network. Among several competitors, Above-Net was the only one capable of overcoming this barrier and delivering a reliable, high-availability and excellent cost-benefit solution.
The solution is made up of a 3G Router connected to the PLC, which in turn connects to the various equipment at the stations. The router remains permanently connected to the Bridgemanager cellular connection management system and is capable of informing the supervisor of the access path of each device connected to the PLC. This way, the customer can monitor various equipment safely and reliably through a single cellular connection.
