Bonding between 50Hz and 60Hz systems

[Spazimspaz]

Greetings all,

I've got a UPS with an input of 50Hz and output of 60Hz with a shared grounding connection between the two systems. For the life of me I can't find a reference that prohibits this, but it just seems wrong as the 60Hz side would be separately derived and doesn't share a common neutral with the source... But that frequency miss match is bothering me... Any help would be greatly appreciated.

 

[LarryFine]

There should be no issue with two separate systems with different characteristics to share common equipment grounding and/or grounding electrode systems.

A single connection between two otherwise-separate systems does not provide a pathway for currents to flow between the two systems. The POCO does it all the time.

Even inadvertently interconnected grounded conductors should be okay. It's kind of like a positive-ground car and a negative-ground car touching metal bumpers.

 

[winnie]

For the life of me I can't find a reference that prohibits this, but it just seems wrong as the 60Hz side would be separately derived and doesn't share a common neutral with the source... But that frequency miss match is bothering me... Any help would be greatly appreciated.

The frequency mismatch is irrelevant. A separately derived system needs to be bonded to ground unless you are intentionally creating an ungrounded system.

Trying to read between the lines, are you saying that the supply EGC is being used as the output GEC? A separately derived system requires a grounding electrode conductor. Since the EGC eventually connects to the grounding electrode system, the EGC _might_ serve as the GEC, but only if it follows the rules of a GEC. See this discussion: https://forums.mikeholt.com/threads/using-egc-as-gec-for-transformers.2573678/