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Optical ground wires (OPGW) must be able to fulfil the regular functions of a ground wire, such as lightning protection and fault current path, as well as provide secure communications by way of the optical fibres embedded inside. Fault current tests were performed on a loose-tube design OPGW to evaluate the temperature and optical performance during and after fault current pulses or 'hits'. Optical performance was found to be affected as early as the fist rated fault current hit. Temperature Gradient tests revealed much higher than expected optical core temperatures, with resultant buffer tube damage. A temperature gradient prediction computer program was developed and independently verified the measured temperatures. A redesign of the cable will be necessary to ensure adequate optical performance for rated fault current hits.

Three different designs of fibre optic ground wire were tested in the laboratory under aeolian vibrations and galloping motions. The purpose of the tests was to evaluate the ability of the cable to withstand specified vibration levels. The optical fibres were continuously monitored for attenuation due to the effects of vibration. The results showed that all three cable designs met Ontario Hydro's requirements.