Why do we need insulators?
Towers and masts which act as radiators generally have to be insulated from ground, and in the case of guyed masts also from the guy cables. In addition, guy cables and other masts or towers located close to the radiator(s) must be insulated and broken up into some fraction of the wavelength so as not to re-radiate the signal and cause interference.
Base Insulators
Base insulators are used in the legs of self-supporting towers and at the bottom of guyed masts to insulate the structure from ground or isolate sections of the tower or mast.
For self-supporting towers the assembly can be arranged so the insulator can either transmit tension and compression as well as shear while keeping the porcelain in compression as in the "cage" type insulator. The other type known as the "oil filled" type uses a fibreglass link as the tensile element whilst in compression and shear loads are taken by the porcelain sleeve.
For guyed masts the unit is always in compression. The insulating material is generally porcelain, but other non-conducting materials have been used. These units are of the "compression cone" or "oil-filled" type.
