Just a thought have you put a Clamp meter on the incoming supply to see what the Comp is pulling Amperage wise?
Great minds think alike?
That's exactly what i was trying to imply. You can get a huge inrush between switching contacts.
main breaker. If we extend the timing breaker from substation goes trip.
Not sure what is meant by this? 10secs as previously mentioned is already on the long side.