Enhanced circuit protection for SCADA/RTU systems

Process automation projects are most often driven by bottom line results, return on investment and an appropriate value position or justification. More and more, systems are expected to:

• Provide access to quantitative measurement points of important processes
• Detect and correct problems immediately
• Measure trends
• Pinpoint and eliminate bottlenecks
• Control larger and more complex processes within a large geographic area
• Maintain constant communications and an uninterrupted power source

All of this can be accomplished with the use of a SCADA system within the automation process. However, none of these functions are available if the system is not designed with a reliable power source for the remote panel portion of the SCADA system.

The focus of this article is to address the need to use the latest circuit protection technology available to increase the efficiency of a battery powered remote panel deployed with a SCADA system. Before we can go into the details of the newest circuit breaker technology for SCADA systems, we need to review what a SCADA system is and its function within the automation process.

Introduction to SCADA

Supervisory control and data acquisition, better known as SCADA, is not considered a technology, but rather a type of automation application. SCADA is used in systems where real time data is mandated and is gathered from multiple areas or locations of the automation process located anywhere from a few hundred feet to miles away from a central control panel.

SCADA systems provide sensing and monitoring capabilities, as well as the computational power to track everything relevant to the process and manufacturing operations. This is accomplished with the use four basic component groups:

1. Sensors and instruments: Devices measuring the variables of the process connected to a dedicated controller.

2. Remote telemetry unit (RTU): Small computerized units deployed in the field at specific sites and locations. RTUs serve as local collection points for gathering data from sensors and delivering data & commands to the master unit (See Fig. 1)

3. SCADA master units: Typically an industrial grade PC which displays detailed graphics of all the field devices and has the ability to process multiple communication interfaces and protocols. The graphics represent the actual field devices in the form of a gauges or some type of device status, such as pumps, flow meters, tank levels, temperature gauges, and switch position.

4. Communication networks connect the SCADA master units to the RTUs in the field: There are many communication interfaces and protocols available from very simple to very sophisticated with extremely high speed and large volumes of data. Early SCADA systems used basic serial communication, running at a very slow speed of 1,200 baud (number of times the signal changes in a second) over a radio-based transmitter/receiver. This approach worked fairly well for the amount of data required over radios with relatively short distances. Today, typical systems are operating at 100 Mbits/s over similar radio technology or wireless Ethernet technology, allowing communication now to reach distances of 10 to 20 miles consistently.

Fig. 1: RTUs serve as local collection points for gathering data from sensors and delivering data & commands to the master unit

SCADA in automation processes today

SCADA is currently used across multiple industries to gather real-time data and communicate back to system engineers. Table 1 outlines some examples of how SCADA systems are currently being used today. This table barely scratches the surface of the potential uses of SCADA systems. SCADA is incorporated in nearly every industry and public infrastructure project anywhere automation is used to increases efficiency.

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