... this standard GB/T18813-2002 standards, and provides the requirements for transformer copper, testing methods, inspection rules, marking, packaging, transportation, ... than 0.20 mm of the strip, the test results for reference only. Table 3, the electrical properties of stripTrademarkConductivity /% ... test conductivity.Conductivity = 100% × 0.017241 / resistivity measured. copper foil for transformers