本指南推荐了天然酯基（如植物油）绝缘液体的测试和评估程序，以及维护标准和方法。还描述了天然酯基绝缘液体的修复、现场应用和诊断方法。

This guide recommends tests and evaluation procedures, as well as criteria and methods of maintenance, for natural ester-based (e.g., vegetable oil) insulating liquids. Methods of reconditioning, field applications, and diagnostics of natural ester-based insulating liquids are also described.