The integrated protection device to implement all the protection and control of the substation is developed， and the corresponding integrated digital substation automation system is designed according to the features of medium and low voltage substations and the standard IEC 61850. The overall structure of integrated digital substation automation system is introduced and the schemes of sampling through process layer， the trip schemes with generic object oriented substation event（GOOSE） and the integrated protection device design schemes are described. The tests of reliability of sampling through the process layer and the real-time characteristic and reliability of GOOSE network show that the schemes can meet the requirements of actual project operation. The designed integrated digital substation automation system has been applied in a practical project.