how to use surge arrester block of simpower system

I'm right now making a simulation regarding the switching surges in our 23kV distribution network. The first problem i encounter are the parameters of the surge arrester namely Vref, Iref, K1, alpha1...and so on. Can you tell me how to get these values. Is it ok not to change the k and alpha values since the HELP says that these values are derived from commonly used arrester? We are using a normal duty arrester with MCOV of 15.3kV and 18kV operating voltage. I also attached the voltage-current curve of the said arrester.

https://www.box.com/shared/d2hd279uwtskbh741fhr

I tried the compute for the values of the parameters using the curve but i can't determine if I'm doing it right. Hope someone can tell me the right way of determining the parameters. Thank you very much in advance

[Ram Patil]

Please incorporate rated voltage of surge arrester as (Vref)(for this exceptional case) of 22 kV system. here number of columns must be one only. For (Iref) please insert reference current i.e. leakage current of Arrester at MCOV. For 22 kV system Arrester leakage current must be less than 5 mA. Regarding Segment Characteristics, dont change these parameters as this is non linear block & there will not be more change.

Answer 1

[Joel Van Sickel]

Copying Ram's post into the answer section.

Ram Patil on 14 Jan 2016

Please incorporate rated voltage of surge arrester as (Vref)(for this exceptional case) of 22 kV system. here number of columns must be one only. For (Iref) please insert reference current i.e. leakage current of Arrester at MCOV. For 22 kV system Arrester leakage current must be less than 5 mA. Regarding Segment Characteristics, dont change these parameters as this is non linear block & there will not be more change.