The pilot was spraying a paddock which required the aircraft to fly over a main power line near the southern boundary. At the completion of a spray run, the aircraft collided with and severed the top three cables of the main power line. The pilot decided to return to Quirindi to land and inspect the aircraft for damage. Before landing, all checks were completed including a functional test of the brakes. The landing was normal until the latter part of the landing roll when the aircraft commenced to veer to the left. The right brake failed as the pilot attempted to correct the swing. The aircraft ground looped, during which the right main gear leg and right flap were damaged. During the wire strike, electrical arcing had burnt a small hole in the right brake line. Although the right brake tested normally prior to landing, brake fluid escaped from the hole during heavy brake application on the landing roll. This report is based on information provided by the pilot.