THE PLT & OBSERVER WERE ON A POWER LINE PATROL FLT. WHILE PROCEEDING SOUTHBOUND, THEY APCHD AN AREA WERE THE LINES WERE ABOUT 23 FT AGL & WERE CROSSED BY ANOTHER SET OF POWER LINES, ORIENTED IN AN EAST-WEST DIRECTION. THE OTHER POWER LINES WERE ABOUT 45 FT AGL WITH 2 STATIC LINES APRX 15 FT HIGHER (60 FT AGL). BEFORE REACHING THE PERPENDICULAR LINES, THERE WAS A PROMINENT MARKER ON THE 4TH POLE NORTH OF THE HIGHER LINES THAT WARNED OF THE CROSSING POWER LINES, 1000 FT AHEAD. AS THE HELICOPTER WAS CROSSING THE PERPENDICULAR LINES, THE RGT SKID BECAME ENTANGLED WITH THE NORTH STATIC LINE. THE HELICOPTER THEN NOSED DOWN & COLLIDED WITH THE LOWER SET OF LINES THAT WERE BEING INSPECTED. IT THEN CRASHED TO THE GND & BURNED. THE HELICOPTER WAS EXTENSIVELY DMGD BY GND FIRE. NO PREIMPACT MECHANICAL PART FAILURE OR MALFUNCTION WAS EVIDENT.