Insulation Tests for the Design and Uprating of Wood-Pole Transmission Lines

Since the demonstration that the switching-surge strength of suspension insulators is markedly influenced by the tower from which it is suspended, considerable test work has been done to evaluate this effect on steel and aluminum structures. An extension of this test work to wood-pole structures shows unexpected advantages in switching-surge strength due principally to the smaller electrical mass of the wood, but in part to its insulating properties. New evidence is also obtained on the reseal property of wood insulation, though causal relationships are not yet understood. Impulse strength tests of wood-porcelain systems corroborate and expand on prior findings.