Earthing or Grounding of Diesel Generator Plant is important to ensure correct operation of the plant and safety of the people who work over there. Generator neutral (star point) is to be connected by insulated earthing conductor through the neutral earthing link or device to main earthing bar. Neutral earthing conductor is to be suitably sized to carry maximum earth fault current for time it takes the system protection to operate with final conductor temperature not exceeding 160 deg. C, but not less than 30 mm2 per 100 kVA of generator rating, with a minimum of 50 mm2. All emergency power diesel gensets including portable gensets to be connected to grounding conductor.
Also read: Guidelines for installing emergency power diesel genset.
Generator earthing terminal is to be connected to main earthing bar by bare copper conductor of cross section not less than 20 mm2 per 100 kVA of generator size, with a minimum of 35 mm2.
Control Gear: Earthing terminals or bars of control gear are to be connected by separate protective conductors to respective main distribution board earth bars.
Extraneous conductive parts including steel frames, battery racks, day-tank, pumps and piping are to be connected by bare copper earthing conductors to main earth bar in compliance with bonding regulations.
A general query found when portable generators used: "Do all diesel generators need to be grounded? What about "portable" diesel generators? Is it more of a concern when a generator is wired into the electrical panel of the home?"
Yes, by all means! But in real life, Operators of Portable genset particularly less than 100 KVA seldom use ground wires. If your first concern goes to safety, all gensets to be properly connected to earthing.