The pilot reported that the glider collided with power lines during an outlanding, cartwheeled and landed inverted. The pilot was trapped for thirty minutes before being able to free himself. The accident occurred at the end of a 500km distance badge attempt. The pilot, who was visiting from England, had assessed his position over the Warby Hills as being satisfactory for a final glide into Benalla. After leaving Warby Hills he encountered sink and diverted to land on a known emergency landing strip on the north shore of Lake Mokoan. The sink was heavier and more persistent than expected and the pilot had to manoeuvre to land in a field short of the emergency strip. The pilot noted power lines on the approach, however the sink was such that he was unable to avoid colliding with them. Significant Factors The following factors were considered relevant to the development of the accident: 1. The pilot was forced to carry out an outlanding. 2. The pilot misjudged the approach. 3. The pilot was unable to avoid power lines on the approach.