Oil-filled cable is characterized by low-viscosity insulating oil filled into the cable insulation. The oil supply maintains a constant pressure to eliminate air gaps within the insulation. It is a representative product of "pressure-type" wire. It is primarily used in high-voltage (110 kV and above) and high-capacity applications, such as trunk lines in urban power grids and incoming and outgoing lines to large hydropower and thermal power plants and hub substations.
Oil-filled cable has a history of approximately 70 years. The first 130 kV oil-filled cable was installed in Italy in 1924; the United States first used 132 kV oil-filled cable in 1927 and completed the first 220 kV cable installation in 1934; France developed 425 kV oil-filled cable in 1955; and Japan has begun developing and trialing 750-800 kV ultra-high voltage oil-filled cables. Therefore, oil-filled cables have a relatively mature set of technologies and experience in both manufacturing and operation, and even in my country, they have been used for over 30 years.
