How to Draw Transformer BIL/Surge Arrester Coordination Plot

[user1011]

Hello everyone,

I'm trying to create a transformer insulation - surge arrester protective level coordination plot similar to the one below. My questions are:
a. Where do i find the duration of Surge Arrester Front of Wave (FOW), Lightning Protective Level (LPL) and Switching Surge Protective Level (SPL)? I only see the current impulse waveshapes from the manufacturer's data.
b Where do i find the duration of insulation levels for the transformer.

I already have the calculation for the protective margins but stuck on replicating the plot below. Thank you in advance for your responses.

 

[protoslash]

look at the arrestor data sheet again, the clamping voltage (or residual voltage or discharge voltage) should be given for multiple surge waves. The most common one is 8/20 micro seconds 10 kA. this clamping voltage is the kV that develops across the arrester when the arrester is subjected to a lightning impulse current wave that takes 8 us to rise to 10kA and 20 us to fall. The time you're looking for is the 8 or 20 micro sec depending how you want to graph it.

the data sheet will also provide the FOV clamping voltage, this should be in the range 1 or 2 micro sec.

the lightning one is the 8/20 micro sec, and multiple current should be provided, which correspond to multiple kA lines in your plot at 10 us.

the switching surge is the 45/95 micro sec range.

the temporary overvoltage (TOV) capability makes up the remainder of your plot.

 

[user1011]

Thank you for the reply, protoslash.