Earthing of 250kva Diesel Generator

Blummin' 'eck. The answer is so simple, mate, I'll spell it out for you.

F O L L O W T H E E L E C T R I C A L S A F E T Y C O D E

A P P L I C A B L E I N T H E C O U N T R Y O F I N S T A L L A T I O N

If you can't find a copy, Dodgy Dave has got three in his lock-up. Just send cash. <Splutter, wheeze>

that was not helpful. can i please get some genuine help from anyone?

Are you using a transfer switch with your generator? If so, are you transferring the neutral?

no we are not using transfer switch.the operation of all DG's are isolated and whenever we need ulility supply for any outgoing feeder we make use of 4-way changeover switch(manual).

i) Run two properly sized Copper or GI Earthing Conductors from the Neutral Bushing/Terminal of the DG Set's Alternator and connect one each to the two neutral earth pits. Similarly, the alternator will have two earthing terminal on its body (at diagonally opposite ends); Run two properly sized Copper or GI Earthing Conductors from these body earthing terminals of the DG Set's Alternator and connect one each to the two body earth pits. But, you MUST inter-connect all these four (two neutral and the two body) earth pits by properly sized Copper or GI Earthing Conductor.

ii) The neutral to earth tapping may be taken at the alternator terminal box or in the Control Panel or in the PCC - as it conveniences you BUT it must be tapped before the neutral is taken for load distribution.

iii) You MUST make an Earthing Grid by connecting all existing and new earth pits. Even though connecting the DG Set's Neutral and the Body Earthing to this grid is logically correct, as per IE Rules, the DG Set (Neutral as well as body) should have two seperate and distinct connections to earth with individual earth electrodes

(Vide IE Rule No. 61 Sub-Rule 1 (a): "Connection with earth: (1) the following provisions shall apply to the connection with earth of systems at low voltage in cases where the voltage normally exceeds 125 Volts and of systems at medium voltage: -

[(a) Neutral conductor of a 3-phase, 4-wire system and the middle conductor of a 2-phase, 3-wire system shall be earthed by not less than two separate and distinct connections with a minimum of two different earth electrodes or such large number as may be necessary to bring the earth resistance to a satisfactory value both at the generating station and at the sub-station. The earth electrodes so provided, may be inter-connected to reduce earth resistance. It may also be earthed at one or more points along the distribution system or service line in addition to any connection with earth which may be at the consumer's premises.]

IE Rule No. 61 Sub-Rule 2: "The frame of every generator, stationary motor, portable motor, and the metallic parts (not intended as conductors) of all transformers and any other apparatus used for regulating or controlling energy at all medium voltage energy consuming apparatus shall be earthed by the owner by two separate and distinct connections with earth.").

iv) Yes! They must be kept isolated to avoid circulating currents when operated in parallel. Only the larger source's neutral is earthed.

thanks a lot.

As i am using copper strips for earthing,can i use aluminium cables(with aluminium thimbles) to connect the neutral in the generator bushing and the earth pit?

And also what's more practical going with the IE code in keeping the neutral and earthing pits separate or connecting all the pits and form a earthing grid and do bonding of neutral and earth?

Start here.