generator star point contactors are keep burning

dear all 

we have 4 gen-sets Cat 3516 working in parallel and thier is a contactor installed to connect the neutral to earth for every generator , but  these conractors are keep burning one by one , so that every month we have to replace one of them 

keeping in mind that we already measure the earth current during the normall operation and it was normal 

have any one an idia about the reason for that 


Re: generator star point contactors are keep burning

Neutral cables from generator (star) must be directly connected to earth (not on contactor), not to GCB. And neutral on load directly connect to earth.
If you disconnect neutral, then 380 ac will be insted off 220 ac. It's may be reason of burning coil 220 ac of GCB.