Abstract: In view of the lack of protection scheme for longitudinal fault in existing protection device,firstly,the characteristics of single-phase and two-phase line broken faults of the line are analyzed under the neutral point grounding and ungrounded modes of the transformer in 110kV load station. Secondly,according to the characteristics of line breaking faults,line break protection based on the compensation of zero sequence voltage differential principle of double terminal zero sequence electrical quantity is proposed to realize the fast and reliable action of line disconnecttion fault. Finally,the disconnection protection logic is added to 110 kV longitudinal differential protection device,and the transmission system of 110 kV load station is established on digital simulation system,which verifies the effectiveness of disconnection protection.