SCADA (Supervisory Control and Data Acquisition) systems are powerful tools. They provide central office technicians, dispatchers, and managers with the ability to see a company's entire physical footprint.
As information flows from the company's widespread locations up the network into the central office, so too can your command flow down from the office to the branches. Why send a technician out to an overheating equipment room 150 miles away when you can just use the SCADA system to turn on the air conditioning?
Simple, powerful, and effective all describe well-designed SCADA systems.
But what SCADA systems are not is: magic. It can be easy to forget, in a world of browsers and software, that technology still runs on hardware. The internet is just modulated electricity.
So are SCADA systems. For them to work, the hardware that powers them - remote terminal units (RTUs) and master stations - must work. If they don't, that overheating equipment room will go unnoticed until the equipment in it is fried and must be replaced. That leaves companies out the cost of this equipment, as well as the cost of having an ineffective SCADA system. Making sure SCADA systems work entails proactive RTU troubleshooting, diagnosis, and preventative maintenance.
Pick a tree, any tree. Oak, elm, maple, hornbeam, birch - you can even pick a shrub, like a rhododendron, or a grass, like maize. Even though it's a single plant, it can have hundreds or thousands of leaves.
Water enters a tree by its roots. Water and nutrients travel upward to the inner bark and into the leaves. These nutrients feed the tree. In the fall and winter, trees detect a decline in temperatures and a loss of daylight. And leaves fall, while trees maintain their core systems.
SCADA systems work the same way. The tree is your company. When your RTUs and their attached sensors along the tree notice a change such as high temperatures, high water levels, or unauthorized entry, it sends a signal.
Upon receiving the signal, your dispatchers or managers, approve an appropriate response, like turning on the air conditioning or the sump pump, or locking the door remotely. Sensory organs transmit information to central processors which take informed action.
The whole system depends on the RTUs. If the RTUs spread throughout your network don't collect accurate alarm data in a timely way, and they aren't reported to an alarm collection manager, you won't know your equipment is in trouble until it's already broken.
The best way to prevent this is to test each RTU regularly, fix the ones that aren't working, and ensure you have an alarm collection manager for effective reporting. Here's more:
RTU checks should be performed regularly, at least once or twice per year. To maximize efficiency, RTU checks can be performed at the same time as technicians test the other equipment on site.
RTUs should be tested in several ways. The most effective way to test an RTU involves using a test fixture specifically designed to work with your equipment. Using a test fixture helps answer these three questions, and then you can move to RTU troubleshooting and diagnosing your problem:
If the RTU doesn't turn on, and the power isn't working, check the fuse. If it's missing or blown, replace it. And, if the fuse is fine but the RTU still won't work, it may have suffered lightning or other serious damage. This RTU will need to be replaced, or brought into the shop for more extensive repairs.
A test fixture is used to test the RTU's inputs. It can simulate the discrete and analog outputs which the RTU monitors. Each input should be tested. The RTU is working correctly if it detects the signal, and then an alert (however you've configured it) is communicated to a master station.
For each input, the RTU must be able to collect the correct data.
If the RTU doesn't detect a signal, the sensor may need replacement or repair. If the sensor is fine, check the wiring. And, if an RTU detects a signal but doesn't communicate the right data immediately, test, repair, or replace the transmitter.
In addition to physical testing, RTU diagnoses can come from the RTU's event logs. Do the logs agree with the log of the relevant central alarm master station? Has the RTU recorded events which were not communicated? Reviewing these logs can provide valuable insights into the condition of the RTU, as well as typical conditions at the equipment site.
Trees need leaves to thrive and grow. Companies need their remote sites to power their operations.
Knowing when these sites are threatened enables companies to respond quickly and effectively before a system goes down.
RTU troubleshooting on a periodic basis ensures that issues at the edge of a SCADA system will be seen and corrected promptly by the central office, delivering a streamlined operation for your company.
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