IEC 60077-1 is the "base" standard, while subsequent parts provide rules for specific components: IEC 60077-1:2017
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Do you need to know the between the older 1999 and the 2017 editions? iec 600771 pdf repack
The 2017 revision updated the 1999 version by updating references to other standards (e.g., IEC 62497-1 IEC 60077-1 is the "base" standard, while subsequent