GB/T 4074.20-1991 "Enameled Wire Test Method Film Continuity Test" is a national standard, which stipulates the test method for enameled wire film continuity (that is, whether there is pinholing or damage). The content includes the test principle (detecting the integrity of film insulation through high voltage), equipment (high voltage test device), sample preparation (enameled wire sample interception), operation steps (applying voltage to detect leakage current) and determination rules (judging film continuity by whether it is broken down). This standard is suitable for mass inspection of various types of enameled wires, providing technical basis for evaluating film insulation performance and production process stability, and helping to ensure the safe and reliable application of enameled wires in electrical equipment.