The static force characteristic of GIS basin-type insulator is the key problem in its manufacture

operation and maintenance.Three dimensional models of 252 kV normal or defective insulators are established in this paper

and stress distributions of insulators are calculated based on the finite element method under different chamber pressures

different crack sizes and different bus temperatures.It is shown that maximum stress is 1.3 MPa and maximum stress appears in the interface of outward flange and insulator bulk when the chamber pressures of both surfaces are0.4 MPa.If the chamber pressures of lower surfaces are 0.1 MPa

maximum stresses is 12.3 MPa.If the chamber pressures of upper surfaces are 0.1 MPa

maximum stresses is 10.9 MPa

but maximum stresses mention above are below the yield strength of epoxy.While there are cracks in basin-type insulators

stress concentrations occur.The stresses of the endpoint of crack change more than those of the midpoint.When the depth of crack is a quarter of the thickness

maximum stresses of crack is 1.3 MPa.When the depth of crack is three quarters of the thickness

maximum stresses of crack is 2.3 MPa.And if the chamber pressures of both surfaces are different

stress concentration of crack will increase by a large margin.With the increase in the bus temperature the stresses are increased

and the maximum stress appears in the interface of the bus and insulator bulk.