What is frequency sensitivity?

Frequency monitoring relays usually detect imbalance between load and power generation and can indicate abnormal operation of the system due to overload or short-circuit. It may indicate overall distress in the system rather than a direct failure of a particular device and can be due to failure of a power device. Protection relays used in systems with high ambient temperatures, high switching frequencies, etc. are sensitive to changes in frequency as per the specified load and power. Under-frequency can result in thermal heating and over-frequency can result in reduced insulation and lead to short-circuit. Frequency sensitive relays can be protection or monitoring relays and are sensitive to under-frequency, over-frequency and differential frequencies.