This paper summarises the activities undertaken when using antennas (ultrasound and radiofrequency) for identifying insulators in pre-failure state by detecting the noise emitted by the distribution line and correlating this with these insulators (porcelain pin type) dielectric breakdown. This has led to developing low-cost maintenance procedures and providing support and criteria for engineering decisions regarding replacing these insulators. The technique used two detectors; a radio frequency detector was used in a first investigation of a particular distribution line, set to 40 MHz and installed on the roof of a moving vehicle. The ultrasound detector was used for inspecting (phases A, B, C) each structure (pole) selected. Atmospheric conditions had no influence on defining pre-failure insulators (pin type) based on the noise detection technique. Pin type insulators emitting noise should be replaced since measurement was made from the ground and near the base of the post.