Comparing with the turbo-generators， a large hydro-generator generally has many branches in its winding for each phase， and then the number of branch windings which be connected to each neutral point may be different. As result， the internal fault protection performance of large hydro-generators has some difference. By the dynamic simulation experiments， the internal fault protections of a model generator which simulates the internal structure and electrical characters of the large hydro-generators are studied. The protections include the differential protection， partial differential protection， split phase and unit transverse differential protection. Based on the comparing and analyzing results of the protection action situation， sensitivity and reliability on the different generator operating conditions， some useful conclusions about internal fault protection performance of large hydro-generators， protection scheme implement and its application are obtained.