Low frequency conduction in oil films and oil-impregnated papers

摘要

In dielectric materials, measurements of the low frequency ac conductivity can often reveal certain features of the electrical conduction mechanism which are often not apparent from the data derived through dc or higher frequency ac measurements alone. In the not too distant past, low frequency measurements were difficult and tedious due to the rudimentary measuring techniques available and the associated instrumentation problems. However, the recent development of a low frequency bridge by Harris1 has changed the situation entirely; now low frequency measurements may be carried out with relative ease in the range from 10?3 to 1 Hz, using the Harris technique.