Dw. Auckland et al., APPLICATION OF ULTRASOUND TO THE INSPECTION OF INSULATION, IEE proceedings. Science, measurement and technology, 143(3), 1996, pp. 177-181
Ultrasonic methods have been employed for the inspection of electrical
insulation, using both the NDT approach (pulse-echo techniques) and b
y acoustic emission. The NDT approach used a commercial ultrasonic fla
w detector to produce A-scans of the insulation system under investiga
tion. A PC scanner system has been developed so that the insulation co
uld be mapped according to the signal depth or amplitude. The acoustic
emission equipment was also a standard commercial system with a 1 MHz
probe. A fiber-optic link was built to isolate the probe and its pre-
amp from the rest of the equipment. Fast Fourier transformation of the
signals into the frequency domain allowed the use of neural networks
for signal recognition. The systems have been utilised to inspect bush
ings, transformers, switchgear and cables for internal flaws, dimensio
nal integrity, partial discharges and water trees.