An isolated 75 MVA generator feeds its own load and operates initially at no load at 3,000 rpm i.e. 50 HZ. A 20 MW load is suddenly applied and the steam valves of the turbine commence to open after 0.5 second due to the time lag in the governor system. Calculate the frequency to which the generated voltage drops before steam flow meets the new load. The stored energy for the machine is 4 kW-sec per kVA of generator capacity.