6kV 10.5MW Generator Neutral Grounding: Why Use 50 Ohm Resistor & Earthing Well?

Hi All!

My project is about a 6 kV, 10.5 MW diesel powered generator, inside a petrol chemistry faciliy. The vendor of the diesel-generator set recommend a switchable grouded neutral point, with 50 ohms resistor. The power plant is in an existing facility, but in a new building, on a clear space. The generator will be connected to the 6/20/120kV substation (power company). The secondary LV energy will be provided from the facility power system, using  NYCWY 4x240/25 cables, so the neutral connection is assured. The MV cables between the generator and the power company substation will be N2XS(F)2Y 3x300/25. Could anybody answer to my questions:

-why the neutral switch is required?

-what are the recommendations for the new grounding system: grounding net around the generator building is enough (the generator's neutral point connected to it), or earthing well is reuired too (the management of the facility wants a well). 

Thank you for your answers!

Hi Zoltan,

neutral point grounding, as I remember this goes to stability of the system and protection to possible faults. There are different types of fault in which as a designer you have to consider those things as much as possible. If you do have image or basic diagram related to this case, it can help us to further discuss this issue.

Hope it helps.

Best,
Neil

Thanks. Wartsila told me that the earthing of the generator starpoint is required only during the synchronisation. After it is not necessary so it can be break with a switcc. If there is an FN fault in the generator, the fault current will flow through the ground to the substation, where there is a resistor too.