Health diagnosis scheme for in-service low voltage Aerial Bundled Cables using super-heterodyned airborne Ultrasonic testing

Insulated Aerial Bundled Cables (ABCs) are preferred over conventional bare conductors in power distribution networks. ABCs offer higher safety and reliability, reduced operation costs and lower power losses. These cables are also lesser prone to electricity pilferage. However, ABCs are susceptible to multiple failures once installed in coastal areas. The damage to the conductors is usually hidden under the insulation; thereby making visual inspection impossible. The responsible maintenance agency hence requires sophisticated solutions for degradation trend assessment of such electrical infrastructure. This paper proposes a novel framework to discriminate between healthy and degraded ABCs of varying degrees, installed in coastal regions. Super-heterodyned ultrasonic listening is used to capture the cumulative damage (insulation weakening and corrosion of concealed metal conductors) in Low Voltage (LV) ABCs, using partial discharge principles. Hilbert Huang Transform (HHT) is applied to the acquired ultrasonic signals to extract time-frequency-energy features. The proposed framework is also used to assess the progressive degradation rate of ABCs installed at multiple locations in the coastal region, with varying exposure to coastal weather. The proposed scheme is effective in identifying the degree of damage and classifying the operational state of the installed ABCs, also making prediction of remaining useful life possible.