This slide depicts the standard 8/20 micro-second and 2m-second current surge wave forms used to test ZNRs®. A 8/20 micro-second wave form simulates a lightning surge. Panasonic uses this wave form to measure the “maximum peak current” and the reference current in order to obtain the “clamping voltage”. The 2m-second wave form simulates a switching surge and is used to measure the “maximum energy” dissipation of the device. When choosing a ZNR, the “impulse derating” plot data should be consulted in order to choose the correct device for the expected peak current, width of the surge current, and of surge impulses. This graph can aid in the selection of a ZNR® by estimating incoming surge values, which are important for surge protection design. To protect against large surges or multiple surges, a ZNR device with a large diameter should have a surge handling capability proportional to the ZNR diameter.