Porcelain pole arm is a kind of cone or pillar type insulator used for overhead electric power circuit. Compared with hypothetical circuit of normal insulator, its strong points as following:
      Rotating structure is applied. When circuit is disconnected, tension unbalance of conductor may rotate porcelain pole arm to effectively relieve expanding of disconnection incident.
      High insulation level and lightning resistance of circuit; low rate of failure.
      Porcelain is easily to be cleaned by rain. Good self-cleaning performance. Breakdown is not easy. 
      Easy construction. Saving steel and wood material.