The causes leading to malfunction concerning rotor’s single point grounding protection for four generators in the second - phase of Shenhua Dongdaliuta Thermal Power Plant have been analysed. It is considered that the main cause is the shaft of generators hasnt actually earthed. The leading wires of carbon brushes installed on the shaft and making contact with the shaft have been connected into the protectiion device after earthing firstly through resistance

the said problem being solved.