Temporary Events: :
Temporary event identification has long been used in the analysis of power systems. It is a very short period of time when the frequency reaches up to 3 MHz. The transient event seen in the wave form of the voltage can be examined in two parts as pulse and oscillating.
The pulses are sudden and unidirectional (positive or negative) distortions occurring in the current and / or voltage. The causes of temporary changes in the form of impact are usually lightning events. It can also affect resonant circuits and may cause oscillatory transient disturbances.
Oscillating transients are bipolar polarities that occur in current and / or voltage, ie both positive and negative values. It is the change of polarity of the current or voltage very quickly. It is also important to note whether this type of disturbance is contained in the basic frequency component. Oscillating transient events are divided into three groups: low, medium and high frequency. Disturbances of more than 500kHz with a basic frequency value of 5μs are high frequency oscillation transient events. Although it can be seen mostly after switching events, it can also occur as a result of the response of the system to temporary events in the form of impacts. Oscillating distortions may occur due to power electronics circuits, communication and snubber circuits. The main frequency values ​​are 5-500kHz and the duration is 20 frekanss. Basic frequency value is less than 5kHz and the duration is 0.3-50ms

The distortions in the range are low frequency transient events. Medium and low frequency oscillation disturbances are observed during the transmission and distribution phase of power systems, especially during energization of capacitor groups.