The pilot reported he had flown to the property to visit some friends. He overflew the paddock in which he intended to land at a height of 500 feet before deciding to carry out a low inspection run to determine if the surface was suitable for a landing. The pilot advised that he had seen a powerline running parallel to the direction of travel. As the aircraft passed along the paddock it struck an unseen spur line running at right angles to the main line. After severing both conductors, the aircraft was flown for a further kilometre before being landed. During the landing roll the aircraft collided with a contour bank.