Today’s water resource managers must protect the resource and also prevent water leakage and contamination during delivery. This task is complicated by the fact that most water distribution infrastructures, which include pipelines and pumps, are located in isolated areas where wired communication devices are not available; consequently they must rely on radio communications.
Using radio communications is cost effective, but a major disadvantage is the limit imposed on data transmission speed. For this reason, operators generally use remote terminal units (RTUs) to log data in local storage devices and then collect the data site by site. However, since in this case data is not transmitted in real-time, implementing video surveillance applications can be difficult.
As a result managers are turning to cellular communications, which is a better solution that features easy deployment, requires no site visits and is suitable for video. With wireless and IP-based cellular communications, operators can easily install cellular modems, data-loggers, I/O controllers and surveillance cameras at remote sites and then manage the data from a central location. Because of these advantages, cellular communications is quickly replacing radio communications.
The first step is to choose the most appropriate cellular RTU solution, with selection criteria including price, hardware specifications and software functionality. However, easy deployment and maintenance, which are often overlooked, should also be considered since such challenges may require a lot of effort after installation.
Challenges of deploying cellular communications
Static public IPs
For most cellular solutions, both the cellular modems at the remote sites and the scada server at the central site should be assigned static public IPs in order to establish bi-directional communications. However, cellular network carriers charge higher monthly fees for static public IPs than dynamic private IPs. Since cellular fees are charged monthly, budget could be an issue. For this reason, managers may decide to shut down some remote sites.
Data consistency
Cellular communications helps users collect data logs from remote sites without needing to make site visits. During data transmission, it is challenging to ensure data consistency through cellular communications given that signal quality and downtime may vary by location. An ideal data-logger should be able to re-transmit data-logs after cellular reconnection, while avoiding transmitting duplicated data so as to reduce transmission cost.
Hodgepodge device management
Some cellular solutions on the market use a hodgepodge of devices, including DTUs (data transfer units), data-loggers, I/O controllers, and video servers. Whether the devices are from the same vendor or not, system integrators must make sure the devices are compatible and properly configured.
Moxa’s ioLogik W5300 cellular RTU controllers
With benefits such as cost efficiency, easy deployment and trouble-free maintenance, Moxa’s ioLogik W5300 cellular RTU controllers have been used in many water and wastewater applications such as pipeline monitoring and automated operations at lift or pump stations.
Dynamic private IPs with active OPC
Most cellular solutions require static public IPs to allow the central site to query the data-loggers at any time. Moxa’s ioLogik W5300 series and Active OPC software allow users to subscribe to a dynamic private IP data plan for the RTUs. The ioLogik W5300 can automatically establish communications with the OPC server using a fixed IP and the server will receive and register the ioLogik W5300’s IP address and receive or record tag updates accordingly. The RTUs are very easy and cost effective to deploy and manage in a dynamic private IP environment.
Data consistency with DA-Center
Collecting data-logs over the air from a central site is one of the benefits of using cellular RTUs. In an ideal operation, the cellular RTUs should be able to retransmit data-logs after cellular reconnection. With Moxa’s DA-Center, this task is much easier as the DA-Center provides a standard OPC interface that interacts with Active OPC Server for real-time data collection. After each cellular connection, the DA-Center will compare the historical and the real-time data and then ask the ioLogik W5300 RTUs to re-transmit any necessary data-logs.
All-in-one solution: cellular modem, data-logger, and I/O controller
In order to reduce the amount of effort required to integrate devices from multiple vendors, the ioLogik W5300 RTU combines a cellular modem, data-logger and an I/O controller in one compact box. If more I/O devices are required, the RTU’s I/O channels can be expanded by connecting it to the ioLogik E1200. If a video server is required, it can be integrated using Moxa’s VPort 461 products. In addition, all products from the ioLogik W5300 series, ioLogik E1200 series and the VPort 461 support a wide operating temperature range for use in harsh environments.
Since many water resource managers are now looking for cellular RTU solutions to replace radio communications, knowing how to select the best cellular RTU is extremely important. The major concerns that managers must consider are deployment effort and maintenance costs. A well-designed cellular RTU delivers reliability, compatibility and integration solutions for a wide range of water and wastewater applications. Using dynamic private IPs and achieving data consistency reduces the cost and effort for both deployment and maintenance.
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