What is substitute leakage testing?

Alternative or substitute leakage is measured using a technique similar to that used when measuring insulation resistance, although it uses a reduced test voltage, typically 40V AC. A test voltage is applied between both live conductors (Line & Neutral) & the protective conductor (Earth) during a Class I test, or a test probe connected to exposed metal parts during a Class II test. The resultant current is measured & then scaled to indicate the current that would flow at the nominal supply voltage.