Evaluation of Impulse Parameters for
Standard Lightning Impulses

1. Raw Data

The raw data are available in the respective measuring channel and subject to store in the database or in an ASCII-file for later availability.

2. Smoothed Raw Data

The raw data are smoothed by 200MS/s with a smoothing interval of 20 samples and temporary stored in the virtual evaluating channel.

3. Zero Line

is calculated as the mean value of 50 samples before the virtual origin T0.

4. Peak Value

The peak value is calculated as the highest sample of the smoothed raw data.

5. Time instant T30

is calculated by linear interpolation as the 30% value of the peak value from the smoothed raw data.

6. Time instant T90

is calculated by linear interpolation as the 90% value of the peak value from the smoothed raw data.

7. Virtual Origin T0

is calculated with T0 = T30 - (T90 - T30)/2.

8. Front Time T1

is calculated with T1 = (T90 - T30)/0.6. 

9. Time-to-chopping Tc

1.   Tc is pre-determined as the first value smaller than the peak value for front chopped impulses or as the first value smaller than the voltage at chopping for impulses chopped in the tail.

2.  Tc is calculated as the cross section of the peak value respectively of the voltage at chopping instant for impulses chopped at the tail with a straight line determined by the 90% value and the 50% value of the breakdown lapse. 

10. Time to half value T50

T50 is calculated as the 50% value of the peak value by linear interpolation of the raw data smoothed with a smoothing interval of 10 samples.