In order to verify whether inherent transient recovery voltage generated by test circuit meets the require ments of IEC or GB standards

it is necessary to calculate the parameters which can present the characteristics of TRV

and compare with standards. Four parameters

for example

can be described by a two groups of four data envelope consisted of three straight lines. Zero-crossing line L1 can be got by dichotomy. Straight line L2 has two cut points with TRV and can be got by analyzing the characteristics of curve fitting’s first-order and second-order derivative. Straight line L3 contains TRV peak and parallels to the time axis. The two points

the intersection of L1 and L2and the intersection of L2 and L3

are the needed four parameters. Through the examples

this method can meet the test requirements.