The primary purpose of Part 551 is to prevent electrical hazards—such as electric shock, thermal fires, and equipment damage—that arise when a facility operates multiple, interacting power sources. 2. Key Installation Architectures
| Edition | Publication Date | Status | Key Notes | | :--- | :--- | :--- | :--- | | 1st Edition (1979) | 1979 | Historic | Chapter 51 of Part 5 | | 2nd Edition (1985) | 1985 | Historic | | | 3rd Edition (1997) | 1997-05-30 | Historic | Sets out general selection rules | | 4th Edition (2001) | 2001-08-17 | Historic | Replaced IEC 60364-3:1993 | | 5th Edition (2005) | 2005-04-14 | | The most widely used version | | 6th Edition | In Development | Draft | CD study/ballot initiated Dec 2025 | iec 60364 part 551 pdf
Generating sets often feature lower short-circuit fault capacities than the utility grid. Protective devices (breakers and fuses) must be rated to clear faults using the limited short-circuit current available from the generator alone. Grounding and Earthing Arrangements The primary purpose of Part 551 is to
Every generating set must be selected based on: Protective devices (breakers and fuses) must be rated