The JB/T 1544-1999 standard provides a test method for electrical insulating impregnating materials and lacquered cloths under rapid heat aging, using the hot focus oblique method. This method evaluates the durability and Stability of the sample in practical applications by accelerating the aging under high temperature conditions. The test results help determine the performance changes of the material over long-term use to ensure that it meets the design requirements. This standard is important for quality control and durability testing of electrical insulating materials.