What’s the Difference Between Protection Relays vs Control Relays?
19th Apr 2024
Relays are electromagnetic devices that open or close electrical contacts to control circuits. But within this broad category, protection and control relays serve very distinct purposes. Both protection relays and control relays play important roles in electrical systems, but they serve very different purposes. Their differing functions and capabilities drive design tradeoffs to consider. Control relays amplify signals to switch loads Protection relays safeguard equipment Operating speed is critical for protection relays Their differing roles and capabilities drive design tradeoffs that engineers must consider for various applications. What is a Control Relay? Control relays switch electrical loads on and off based on input signals, allowing low power circuits to activate higher powered lights, horns, valves, motors, and more. Their primary functions are signal amplification through contact multiplication and overload protection for delicate switching electronics. Popular examples include starter, timer, latching, and automotive relays. What is a Protection Relay? Protection relays safeguard electrical infrastructure and equipment from excessive currents, voltages, temperatures, frequencies, etc. They continuously monitor system conditions and quickly engage circuit breakers or send shutdown signals when thresholds are exceeded. Common types include overcurrent, differential, distance, transformer, generator, and arc-flash protection relays. Protection Relays vs Control Relays – Key Differences Here are a few key differences between protection relays and control relays: Operating Speed Control relays may switch loads on and off frequently, as fast as multiple times per second. Their electromechanical contacts must withstand this high-duty cycle operation over years of hot switching. But operating speed is less critical – 10 to 50 milliseconds […]
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