The test with normalised pulses is compliant to the CENELEC HD 588.1, IEC 6O-1, CEI 42-4 regulations.

This test simulates what happens on an electrical machine when the windings are subject to quick high value voltage pulses, usually generated by atmospheric discharges (thunderstorms), or by intense noises, generated by other electrical machines or by power devices (ex. welders). The connection principle is the following:


avvolgimenti impulsi normalizzati






G  = Variable D.C. generator    R1 = Protection resistor

C  = Charge capacitor               R2 – R3 = Resistors for pulses duration regulation

I  = Electronic switch                 R4 = Resistor for impedance adapting

L  = Inductor for rising time regulation


The wave generated is the following.


forma onda impulsi normalizzati






The 1,2/50 values indicate:

1,2       Voltage rising time (in microseconds). Time necessary for the voltage to go from 0 to the programmed value (T1)

50        Time (in microseconds) in which the maximum voltage is reduced of 50%.

Old or damaged insulators generate a variation in the curve showing the problems detected, for example, the voltage that does not reach the programmed value or that after reaching it suddenly drops very quickly.

Apart from the visual result, the system can provide the visualisation of the result on the green and red LED (GO – NOGO).


Following is a short extract from the CEI 42-4 regulations:

3.1   The distinction between atmospheric pulses and manoeuvres is determined by the duration of the edge. Pulses with edge lower than 20 microseconds are considered atmospheric. Pulses with edge higher than 20 microseconds are considered manoeuvres.

18.1.1    Full atmospheric pulses. A full atmospheric pulse is a lightning pulse that is not truncated by a disruptive discharge (like in picture)

18.1.2   Truncated atmospheric pulses. A truncated atmospheric pulse is a lightning pulse during which a disruptive discharge causes a breakdown of the voltage (the voltage goes next to 0). The truncation can happen during the rising edge, the peak or the falling edge of the pulse.

19.1    Normalised atmospheric pulses. A normalised atmospheric pulse is a full pulse having an edge duration equal to 1,2 microseconds. It is commonly known as 1,2/50 pulse.