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The use of ultrasound for the detection of water trees in XLPE cable

This paper describes a method whereby the frequency content of ultrasonic signals is used to locate water trees in cross linked polyethylene, thus enabling the tree density in cables to be determined non-destructively. A conventional A-scan technique is used to generate an ultrasonic signal representative of the polyethylene under inspection. The time signal is transferred to a computer and transformed to the frequency domain. This signal is then categorized by a Back Propagation Neural Network.