Investigation and modelling of acoustic guided waves in steel grounding rods

A circuit model is presented for a piezoelectric-based, pulse-echo method for detecting the presence of corrosion in grounding rods for power transmission substations. Our pulse-echo method uses an acoustic guided wave generated from a piezoelectric transducer that is sent down the length of the grounding rod. The wave travels down the rod, reflects off the end and travels back to the piezo transducer. The wave's signature is recorded using a Data Acquisition System. The structural integrity of the rod can then be characterized based on the nature of the reflected wave. A SPICE model of the system based on Leach's model has been developed and tested. The electro-acoustic circuit model of the system can predict the overall behavior of the system. A symmetrically driven pair of steel rods was used to demonstrate that the model reproduces the main features of the signal. Defect detection was demonstrated in steel rods containing simulated defects and also in recovered grounding electrodes.