Cross arm and device for on-line monitoring of line

The invention provides a cross arm and a device for on-line monitoring of a line. The cross arm comprises two cross arm supports, a sleeve and a mounting cylinder. The two cross arm supports are fixed to a cross rod at the top end of the electric pole through the support fixing assemblies and are parallel to the cross rod. The two cross arm supports are located on the two sides of the electric pole respectively. The sleeve is arranged between the two cross arm supports, connected to the two cross arm supports in a sliding mode through the sliding assembly and located and fixed through the sleeve locating assembly. The installation cylinder is arranged in the sleeve and used for containing the fault indicator. According to the invention, the cross arm and the fault indicator are combined with each other, so that the cross arm which not only can support the electric wire, but also can monitor the electric wire on line is provided; meanwhile, the distance between the two fault indicators can be conveniently adju