Residential standby generators: Clause 551 ensures that a backfeed prevention interlock is installed – a simple mechanical or electrical interlock between the main switch and the generator input.
Commercial buildings with CHP: Combined heat and power units often operate in parallel with the grid. Clause 551 demands anti-islanding protection (detecting loss of mains and disconnecting within 0.5 seconds).
Construction sites: Portable generators used as sole supply must have appropriate RCD protection and correct earthing (often TT system with local earth electrode).
IEC 60364 is the international standard for electrical installations in buildings. Part 5-551 specifically addresses "Selection and erection of electrical equipment – Low-voltage generating sets." iec 60364 part 551 pdf
While earlier parts of the standard deal with general protection against electric shock, Part 551 focuses on the specific hazards and operational requirements introduced when a building has its own power source. It covers generating sets that are:
A frequent point of confusion in generator installations is the handling of the neutral conductor. IEC 60364-5-551 provides guidance based on the earthing arrangement:
IEC 60364 is a comprehensive international standard series for low-voltage electrical installations. Specifically, Part 5-55 (Clause 551) addresses "Other equipment" – with Clause 551 dedicated to Low-voltage generating sets. Residential standby generators : Clause 551 ensures that
The official title is:
"IEC 60364-5-55: Electrical installations of buildings – Part 5-55: Selection and erection of electrical equipment – Other equipment – Clause 551: Low-voltage generating sets."
This clause covers:
Note: It does not cover generating sets used solely for firefighting systems (covered by other standards like IEC 60364-5-56) nor generators for vehicles. Note: It does not cover generating sets used
This is where confusion often arises. Clause 551 directs you to:
Every installation complying with IEC 60364 Part 551 must include:
Searching for a free IEC 60364 part 551 pdf is common, but be cautious. Unauthorized copies are often outdated, incomplete, or incorrectly formatted. Here is why you should acquire the official document from the IEC Webstore or national committees (e.g., BSI, DIN, AFNOR):
Pro tip: Many national standards bodies offer "read-only" online access for a lower fee if you do not need to download the IEC 60364 part 551 pdf permanently.