The pilot was conducting a charter flight to a property with a student pilot as passenger. The weather in the area of the destination was overcast with local rain showers and thunderstorms. Approaching the property the pilot made a long descent, under the cloud cover, to a low altitude to attract the attention of the property owner so that he would meet the aircraft on its arrival. At the bottom of the descent, as the pilot applied power for the go-around, the aircraft collided with powerlines. Slack in the long powerline span, and its separation from the support poles during the impact, allowed the aircraft to carry forward and land straight ahead on a road. During the landing roll the aircraft collided with heavy farm equipment parked at the side of the road causing severe damage to the tailplane and left hand flap. The pilot and passenger were wearing sunglasses in reduced light conditions which may have contributed to their failure to see the powerlines.