Electrical Resistance
Electricity and Magnetism

Counting the discs

Stories from Physics for 11-14 14-16 IOP RESOURCES

High voltage power lines typically use disc insulators to prevent current entering the metal pylon. Counting the number of discs can give an indication of the line voltage:

Line Voltage (kV)Number of discs
34.53
454
695
927
1158
1389
16111
19613
23015
28719
34522
36023

When winds blow, high voltage power lines respond in three modes of oscillation: Gallop (0.1-0.5 Hz), Aeolian (8-60 Hz) and Wake-induced vibrations (0.5-2.5 Hz). Stockbridge dampers are dumbbell-shaped dampers consisting of two concrete or metal masses attached to a piece of cable or other flexible material. They reduce Aeolian vibration that can cause dangerous stresses in power lines.

References

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