It is a short-lived burst of energy caused by a temporary event or sudden change of state in the system.
The word transient is a derivative of the English word transit and means temporary or short term. In electricity, temporary but very rapid changes on the basis of voltage are defined as transient. In the transient state, it is possible to reach multiple multiples of the instantaneous amplitude in the order of micro or pico seconds in the millisecond sinusoidal waveform. These situations cause the equipment to age or malfunction depending on the amplitude.
It is almost impossible to detect transient events with RMS measuring devices. Special measurement instruments are required that can capture the sinusoidal waveform much faster. At this point, we use devices capable of detecting transient values that reach multiple multiples of the nominal waveform. We can measure transients up to 500 times with direct connection in LV systems, and indirect connection * in MV and HV networks, depending on the case situation.
* Measurements in MV and HV facilities are taken over the voltage measurement transformer. Measurement capability may vary according to the characteristics of the voltage measurement transformer.