Using precise and secure data handling along with efficient protocols makes SCADA cellular data acquisition from remote sites is a cost-effective option. This mobile technology fills a need to connect users to SCADA data, whether they are located in the field, corporate engineering or C-suites. SCADA software solutions like Indusoft Web Studio are working on ways to offer users a wider variety of connectivity options, including the ability to connect to remote sites over cell networks.
Human Machine Interfaces (HMIs), databases and the cloud are well-developed methods to encapsulate and connect users to KPIs, production data, process variable trends and fault histories. A hardwired Ethernet and related protocol, or a local and secure Wi-Fi connection, are often used. More remote machines and processes often use public communication methods such as radio, satellite or phone lines.
Another over-the-air communication option is cellular. Perhaps too expensive in the past, today, proper hardware selection, an efficient protocol, a secure network configuration and a data filter in the controller or HMI can be used to create a cost-effective cellular SCADA data collection and distribution system.
Cellular provides a high-speed connection over a large area. It typically costs less than satellite, and the required hardware is reasonable priced and easy to configure and deploy.
A data provider and a cellular modem, gateway or router are needed to implement a cellular SCADA data collection system. A cellular gateway is a good option as they have been around for about 20 years and can incorporate a firewall and virtual private network (VPN), along with router and modem functionality, into a single device.
Cellular gateways often come with many cybersecurity features as they are commonly used in retail and enterprise applications. These gateways connect to local Ethernet ports via popular industrial protocols like EtherNet/IP and Modbus TCP, and some will even connect to Wi-Fi devices. Typical IP network cybersecurity including encryption, VPNs, port filtering and trusted IP addresses are available and should be used.
Efficient use of cellular data is required to keep monthly charges low. The data cannot bang away on the communication port every second as is common in many hardwired Ethernet systems. User Datagram Protocol (UDP) and Distributed Network Protocol Version 3 (DNP3) can both be employed to limit bandwidth usage.
Instead of using Transmission Control Protocol (TCP), which adds data overhead due to retransmission of data, use UDP. It’s a less common protocol used by Ethernet to send data packets over the Internet. Although it is less reliable, it’s faster and uses much less data to get the job done.
Add DNP3 protocol to UDP/IP, and it guarantees data packet delivery. DNP3 is often used by water, electric and gas companies, so it works well in SCADA applications. It verifies the local machine received and understood the data.
This DNP3 protocol is available with InduSoft Web Studio and inherently reduces communication channel bandwidth while combining some of the best features of other protocols. With DNP3, only the data that changes is reported to and from the SCADA system.
Along the same lines, a cellular SCADA data collection system should filter the data so only the necessary data is sent via the cellular connection. Just the minimum and maximum data is usually required—and all the bits, integers and floating point variables.
Analytics can also reduce a significant amount of data into a smaller amount of actionable information. While many remote tank farms and large pumping stations collect vast quantities of data from the controllers and instruments, a local HMI/SCADA data acquisition system can automatically analyze the data. After analysis, only the relevant, actionable data is transmitted over the cellular network.
For more information, please see the article Using cellular data for SCADA data in the Jan-Feb 2017 issue of InTech Magazine, authored by Marcia Gadbois, formally General Manager and VP for the Wonderware InduSoft Web Studio group of Schneider Electric.