Is advanced feeder protection only for utilities? So far, yes. Very few industries believe that it’s money well spent to invest in advanced feeder protection relays only to improve power quality. ABB’s new middle-class protection relay REX 521 might change some minds.
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"With the REX 521, you get functions previously available only at a considerably higher price," says Aimo Latvala, ABB Oy, Distribution Automation, in Vaasa, Finland. "These include condition monitoring, disturbance recording and power quality monitoring - and of course motor protection."
But isn’t this overkill for an industry plant? Isn’t this a product exclusively for utilities - at risk of being penalized unless they provide end-customers anything short of 100 percent power quality? No, it’s just as useful to industries that want to maximize plant uptime and minimize maintenance costs. Here’s a few examples of what REX 521 will do to your plant:
Thanks to condition monitoring, fault currents related to the wear of circuit breakers are measured continuously. As the magnitude of fault currents are related to the wear of the circuit breaker, you can schedule your preventive maintenance more exactly. You’ll neither wear out the circuit breaker entirely, nor service it too soon - instead you’ll find the optimum preventive maintenance scheme.
Disturbance recording - parameters such as currents and voltages are measured 2,000 times per second to provide a thorough analysis of a fault condition. What is the magnitude of the fault values? What exactly caused the fault? What are its effects on surrounding equipment and processes? The answer to these questions, again, helps you plan a more cost-effective preventive maintenance.
Power quality monitoring means checking for harmonic overtones. Previously, these disturbances - appearing in multiples of 50 Hz - could only be monitored using specific equipment. Now, you can continuously monitor the harmonic content in your network - and immediately take the appropriate action.
"REX 521 is perfect for any industry equipped with medium-voltage switchgear. Even those who simply look for motor protection should have a closer look at REX 521. Because of the low cost, you can actually consider the feeder protection a bonus to motor protection - and an extremely useful one at that," says Latvala.