1. High Reliability
Because the cable insulation maintains a constant pressure, external moisture and air cannot enter the insulation through the cable itself or accessories. Therefore, as long as the oil pressure is normal, the long-term operational reliability of oil-filled cables is not a problem, with a service life of up to 40 to 50 years.
2. Low Maintenance
Because the insulation of oil-filled cables is contained within a sealed system, once the cable line is installed and passed the acceptance test and put into operation, no maintenance or preventive testing is required. Only regular oil sampling and testing during power outages is required.
3. Low Spare Parts Required
Oil-filled cables, both the cable itself and accessories, have a high degree of universality, significantly reducing the number of spare parts.
4. Suitable for Higher Voltage Levels
In recent years, a new type of oil-filled cable with a new insulation structure, the PPLP structure, has emerged abroad. This composite insulation paper is made of two layers of low-loss wood fiber paper sandwiched between a layer of polypropylene film. Compared to ordinary cable insulation paper, it has higher dielectric strength and lower dielectric loss (=2.8*0.001, compared to 3.4-3.7x0.0025-0.004 for ordinary oil-filled cables). This structure is very promising for use in 500-800kV oil-filled cables. Japan has successfully developed this product, and its pilot section is undergoing long-term reliability verification testing.
