Surface contamination and cracks of GIS insulating spacer can reduce the flashover voltage on its surface and seriously endanger the normal operation of power grid. Therefore

the study on condition detection of insulating spacer is of great significance to ensure safe operation of power grid. Based on the modal analysis method

the live condition detection system of insulating spacer is developed in this paper

and such defects as surface contamination and cracks of insulating spacer are tested and studied. The results show that the contamination defect of insulating spacer can remain the amplitude of modal transfer function changed

and the modal characteristics of the insulating spacer are sensitive to the variation of contamination quality. The crack defect can cause the extreme point of the modal transfer function of the insulating spacer to move backward. Under the joint action of the surface contamination and crack

the amplitude variation of modal transfer function in the high frequency band 2 000-4 000 Hz is more drastic and the modal characteristics difference is more obvious. The field test is performed based on the detection system

and the disassembly inspection results show that the detection system can accurately detect the condition of GIS insulating spacer. The research in this paper provides a new method for live detection of condition of insulating spacer in GIS equipment.