OIP vs RIP Bushing: Which Should You Choose?
2026-09-24
Oil-impregnated paper (OIP) and resin-impregnated paper (RIP) are the two most widely used high-voltage bushing technologies. Each has its own strengths and weaknesses — choosing the wrong one affects both safety and total cost of ownership.
Technology difference
- OIP: the main insulation is paper impregnated with insulating oil, relying on an oil-paper composite. A mature technology used for decades.
- RIP: paper is impregnated with epoxy resin under vacuum and cured into a dry, void-free core.
Key comparison
| Item | OIP | RIP |
|---|---|---|
| Insulation medium | Oil-impregnated paper | Resin-impregnated paper (dry) |
| Contains oil | Yes, oil level must be monitored | No, maintenance-free |
| Partial discharge | Low | Lower, more uniform insulation |
| Moisture resistance | Depends on seals | Core itself does not absorb moisture |
| Aging | Oil-paper ages in service | Slow aging, long life |
| Fire / leakage risk | Oil leak and fire risk | Oil-free, safer |
| Initial cost | Relatively lower | Relatively higher |
When to choose OIP
- Projects sensitive to initial investment.
- Existing oil-maintenance systems already in place.
- Direct replacement of specific legacy models.
When to choose RIP
- New projects focused on total cost of ownership.
- High fire-safety requirements (underground or indoor substations).
- Maintenance-free operation with fewer outages.
- Heavy pollution and high-humidity environments.
Overall, RIP is gradually replacing OIP as the mainstream choice for new installations, especially at 110 kV and above. Ever Power offers porcelain bushings in both technologies and can recommend the best option for your operating environment.