Nondestructive testing method for internal surface cracks in underground section of concrete transmission pole

Based on the reinforced concrete pole used in 110kV transmission lines, the paper proposed a new nondestructive testing (NDT) method. The method takes the drainage hole designed originally in the pole as the testing hole. Through the hole, an industry endoscope probe can be inserted to the pole to detect internal surface condition in underground section. To verify the NDT method, a testing pole with simulating internal surface cracks was established. The industry endoscope system transmitted the video images of the internal surface to the monitor outside the pole. Therefore, the operator can assess the pole by observing the images on the monitor screen. The result demonstrates that the method solves the problem of crack detection in underground section of concrete pole and provides an effective nondestructive detecting tool in the routine safety inspection for transmission poles.