Explanation to irregularities in the dependence between voltage sag magnitude and the tripping level for line operated synchronous machines

Voltage sags are huge power quality problems for many industries. Voltage sags may cause tripping, production disturbances and equipment damages. Undervoltage tripping is one way of protecting equipment from getting damaged due to overcurrent during voltage sags. However, the undervoltage protection is usually set to break at an absolute voltage magnitude instead of at a relative voltage magnitude change. This may lead to both unnecessary tripping and nontripping when necessary.