Voltage sag: It is usually associated with system faults but can also be caused by energization of heavy loads or starting of large motors. Voltage sag is the short reduction in the RMS voltage between 0.1 to 0.9 pu for a duration of 0.5 cycle to 1 minute
A form of AC testing that applies voltage and measures the leakage/loss current of electrical insulation. It is a type of insulation testing used to evaluate the integrity of electrical insulation.
The series electromagnet is energized by a coil known as current coil which is connected in series with the load so that it carry the load current. The flux produced by this magnet is proportional to and in phase with the load current.