DG Set

the forth pole is ment for nutral which palys vital role in DG operation

Dear Sir ThanX for yr response. The fourth pole in the DG switchgear is ,as u said, for the neutral.But why should the neutral also get isolated along with the 3 phases ? If not required ,i may as well go in for neutral link.I thought there might be some technical background for the same. Please clarify. regards Ravipra

There are some applications that if generating in stand-alone mode (i.e. the DG is the only source) the neutral must be the DG neutral. But if the DG is playing a part in wholescale generation with other DGs in parallel or feeding onto the grid, then the neutral has to be the grid neutral. Either way, neutral where the DG is connected may not be earth potential depending on any current flowing along the neutral conductor. So if it were not disconnected the DG circuit could still be hazardous.

Dear Sir ThanQ for the response.I am able to gather ,the following from your response: 1)If operating in island mode DG switchgear can be three pole. 2)If operating in a network (in parallel with other DG set or grid) the switchgear shall be 4-pole and the neutral needs to be isolated along with the phases. Further when the neutral of the DG set is effectively grounded ,why should we assume that the neutral is not at zero potential. And how can the current flow in the neutral conductor in violation to the Kirchoff's law? Please respond. regards Ravipra

Lot of activities take place with in the alternator and generate circulation currents due to Hormonics, Low Power factor etc which needs to be conducted to earth through nutral conducter in fact once the single line digram is frozen one has to calculate Fault currents,hormonic currents etc& nutral conducter sized i would sugest you refear Diesel Generator Hand book By LL Mohan you would get all the information you are looking for

Dear sir

ThanQ very much for yr response.I shall also refer to the suggested book.

regards

ravipra