What is voltage sensitivity?

Monitoring relays designed for detection of over-voltage and under-voltage conditions in electrical systems are considered to be voltage sensitive. Single and three phase motors operate at specific voltages. When the motor voltage goes below the specific rated voltage of the device, it draws higher currents to drive the motor resulting in overloading and heating of the motor. The monitoring relay in such a case trips, being sensitive to the voltage drop, to indicate the designed display and also to protect the device, and again picks up after the specified time delay when the voltage is maintained within the specific operating range and the current is also within the operating range. In case of over voltage condition in the system, insulation of the system cannot withstand the exceeded voltage as it damages the devices.