Grounding and bonding [/ˈgraʊndɪŋ ənd ˈbɑndɪŋ/] v - Grounding (connecting the system to earth) and bonding (connecting all metal parts together) are the unglamorous foundation upon which everything else in The Engines of the Hall rests. Done well, the work is invisible; done badly, it yields those intermittent, maddening faults that bring down equipment for no evident reason.

The work is of two kinds:

• Safety / equipment grounding [/ˈsæfɛti ˈɛqʌɪpmɛnt ˈgræʊndɪng/] n - gives fault current a low-impedance path back to the source, so that the protective relays in Medium-voltage switchgear truly trip, and so no exposed metal is left energized.
• Bonding [/ˈbɒndɪŋ/] n - ties racks, cable trays, Busway distribution, and the Rack power distribution unit chassis to a common reference, lest any voltage difference arise between two things a technician (or a signal cable) might touch at once.

Every transformer in the chain, at the Where the Grid Comes In and in the Power distribution unit, creates a separately derived system with its own grounding electrode and neutral-to-ground bond. To set these bonds aright (exactly one per derived system) is what permits a Static transfer switch or Automatic transfer switch to pass between sources without ground loops or nuisance trips.

Because grounding underpins The Current That Comes in Threes distribution everywhere, it is cited by nearly every other entry in these pages.

Part of The Engines of the Hall.