Remote sensing system for faulty suspension insulator units

In Japan, electric power utilities periodically inspect the suspension insulator units on transmission lines. Line workers check the allotted voltage or the insulation resistance of insulator units using a hot stick, an automated faulty insulator detector, or other detectors. For safety and efficiency a remote sensing system is desirable. This type of system is indispensable for UHV transmission lines, since higher electric fields prohibit workers from being outside the tower frame under energized conditions. Most of the faulty suspension insulator units removed from transmission lines have cracks in the porcelain. The vibration characteristics of a cracked insulator unit differ from those of a sound unit. We have developed a prototype system, which can detect a cracked insulator unit at a distance up to 50 m apart from the insulator. The system consists of an acoustic radiator, a laser Doppler vibrometer, and a control unit.