Buried Stub Angle Inspection System

Stub angles of power transmission line are used to anchor and stabilize the lattice tower. The concern of the lattice tower is that its buried portion could be heavily corroded, and it would not be easily detectable from above ground. When the corrosion of these stub angles progresses to unsafe levels, the tower structure could catastrophically fail.

With collaboration from EDM International Inc. and the Electric Power Research Institute, Southwest Research Institute^® (SwRI^®) scientists successfully applied magnetostrictive sensor (MsS) system to differentiate good, lightly corroded, and highly corroded stub angles in laboratory testing. Using symmetric Lamb guided waves at 32 kHz, the stub angles without having braces or attachments in their middle were successfully inspected in field evaluation test.

The figure shows MsS probes installed to inspect a stub angle of 80-foot-tall transmission tower located at the northeast of San Antonio, Texas. The strong end-reflected signal indicated the "good" stub angle.