OIP or RIP Transformer Bushing: What Should Buyers Check?
Compare oil and dry-core construction, mounting, maintenance and model-specific IEC 60137 test evidence before choosing a transformer bushing.
Selection note: use this guide to compare technical requirements. Confirm catalog ranges, typical values and standard clauses against the model, edition and agreed test conditions; project acceptance follows the approved drawings and technical agreement.
On this page
- 01What is the difference between OIP and RIP bushings?
- 02Which bushing is safer in an internal fault: OIP or RIP?
- 03How do OIP and RIP compare on tan delta and partial discharge?
- 04Can OIP and RIP bushings be installed at any angle?
- 05How should OIP and RIP bushing lifetime costs be compared?
- 06Frequently asked questions
- 07Standards & sources
In short
Compare OIP and RIP by the quoted insulation system, installation angle and sealing needs. A dry RIP core reduces internal oil-related maintenance but still needs condition checks.
- Bushing failures can affect transformer safety; evaluate failure mode, monitoring and fire protection for the project.
- Compare the complete housing and failure mode; RIP removes internal oil from the core, while OIP requires oil and seal monitoring.
- Mounting angle depends on the quoted design; obtain the permitted orientation and installation drawing for either OIP or RIP.
- Compare purchase, outage, fire-protection and maintenance costs for the actual project before selecting OIP or RIP.
- RIP cores must be protected from moisture during storage; specify sealed packaging and a storage period with the supplier.
Choosing between an OIP and an RIP transformer bushing is one of the few component decisions that changes the fire risk, maintenance plan and installation geometry of an entire transformer. For procurement, assess bushing failure modes, condition monitoring and fire-protection requirements using the project risk analysis. This guide compares both condenser technologies against the criteria utilities and EPC contractors actually use: safety, dielectric performance under IEC 60137, mounting flexibility, maintenance and lifecycle cost.
01What is the difference between OIP and RIP bushings?
Both use condenser screens to grade the electric field. OIP uses oil-impregnated paper insulation; RIP uses paper impregnated with resin and cured into a solid core. The complete bushing may still have an oil-side interface with the transformer, so check the assembly drawing rather than treating the core material as the entire fluid boundary.
The insulation system changes oil handling and monitoring needs. OIP uses oil within the paper insulation and requires oil containment and seal checks. RIP uses a cured resin-impregnated core, removing an internal oil reservoir from that core; the complete bushing still needs review of its housing, seals, interfaces and fault behaviour.
A further option is RIS (resin-impregnated synthetics), which uses synthetic insulation in the condenser core. If an RIS design is offered, compare its model-specific ratings, interfaces, test evidence and maintenance requirements alongside OIP and RIP.
02Which bushing is safer in an internal fault: OIP or RIP?
A dry RIP core removes the oil held inside an OIP core and can reduce oil-related fire and leakage hazards. Neither insulation type makes the complete bushing failure-proof: housing material, transformer oil interface, fault energy and protection determine the mechanical and fire consequences.
A porcelain housing can fragment during a severe fault, regardless of whether its core is OIP or RIP. Where personnel exposure or fire spread matters, compare the complete assemblies, housing options, site clearances and protection plan rather than relying on core technology alone.
- OIP risk chain: moisture or ageing, rising tan delta, thermal runaway, arc, oil vapour pressure, housing rupture, oil fire.
- RIP buyer check: no oil reservoir in the dry core; still review housing, oil-side interface, fault protection and model-specific tests.
03How do OIP and RIP compare on tan delta and partial discharge?
Both OIP and RIP complete AC bushings need dielectric testing under the applicable IEC 60137 clauses. Confirm the insulation type, applied voltage, temperature and agreed tan delta and PD limits for the offered model. OIP condition monitoring also considers oil and seal condition; RIP still needs checks of seals and insulation condition.
Compare measured tan delta and PD under the same stated voltage, temperature and test method; record OIP oil and seal condition alongside the electrical results.
For condition monitoring, compare C1 capacitance and tan delta trends with the factory baseline and the maintenance procedure. Investigate sustained changes using the applicable guide and site risk assessment.
| Criterion | OIP (oil-impregnated paper) | RIP (resin-impregnated paper) |
|---|---|---|
| Core insulation | Kraft paper + mineral oil | Crepe paper + cured epoxy resin |
| Tan delta acceptance | Confirm by type and clause | Confirm by type and clause |
| Measured factory tan delta | Request model report | Request model report |
| Fire and mechanical fault review | Review oil and housing failure modes | Dry core; review complete assembly and housing |
| Mounting angle | Confirm by oil system and model | Confirm by model; some allow horizontal |
| Routine maintenance | Oil level, DGA, seal checks | Visual check, periodic C1 / tan delta |
| Storage | Store inclined or vertical as specified | Dry, sealed packaging; limited storage time |
| Purchase price | Request a model-specific quote | Request a model-specific quote |
| Service evidence | Request comparable model references | Request comparable model references |
04Can OIP and RIP bushings be installed at any angle?
Mounting limits are model-specific. Some dry RIP designs permit horizontal or inclined installation, while OIP designs must maintain their specified oil coverage and expansion arrangement. Ask for the permitted angle and installation drawing for either quoted bushing.
For compact substations, wall penetrations and GIS interfaces, compare the actual installation envelope and housing mass. Any load or seismic benefit of a composite housing needs the proposed unit weight and support calculation.
“Buyer check: compare OIP and RIP model drawings, dielectric test results, installation limits and maintenance plan before selecting a bushing.”
05How should OIP and RIP bushing lifetime costs be compared?
That depends on the specified designs and the project maintenance plan. Compare purchase price, installation, inspections, outage costs and any oil-handling work over the planned service period; do not assume a universal saving or a fixed lifetime for either type.
Compare purchase price with actual inspection, outage, oil-handling and replacement costs in the project lifetime model.
- Compare a quoted RIP design where site space, oil handling or mounting orientation is a constraint; verify its complete assembly and test evidence.
- Compare a quoted OIP design for a replacement or cost-sensitive project; confirm matching interfaces and the planned oil-maintenance scope.
- For either design, approve the model and manufacturer interface drawing; apply a dimensional standard such as EN 50180/50181 only when it covers the specified interface.
Applicable EONOVA Equipment
Conclusion
Select OIP or RIP only after comparing the approved interface drawing, insulation duty, model tests, mounting and maintenance plan.
Talk to an EONOVA engineerFrequently Asked Questions
Can an RIP bushing directly replace an OIP bushing on an existing transformer?
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Only after interface review. Compare the existing nameplate and drawing with the RIP option for voltage/current, flange, oil-side length, terminal, CT space and mounting angle.
How long can an RIP bushing be stored before installation?
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RIP cores absorb moisture if exposed, so they are shipped in sealed packaging with desiccant or in an oil- or gas-filled transport container. Storage time depends on the packaging; confirm the permitted period with the supplier and measure tan delta before energisation after long storage.
What is the typical service life of OIP and RIP bushings?
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There is no single verified service life for all OIP or RIP designs. Ask for the quoted model documentation and maintenance plan; monitor OIP oil and seals, and assess RIP housing, seals, capacitance and tan delta against its baseline.
Standards & Sources
- [1]IEC 60137:2017: Insulated bushings for alternating voltages above 1000 V
International Electrotechnical Commission
Supports: Scope and test programme for applicable complete AC bushings; check limits by type and clause.
- [2]CIGRE TB 642: Transformer Reliability Survey
CIGRE Working Group A2.37
Supports: Technical context for transformer bushing failure modes; no universal percentage is asserted.
- [3]CIGRE TB 755: Transformer Bushing Reliability
CIGRE Working Group A2.43
Supports: Failure modes, diagnostics and service experience of OIP and RIP bushings.
- [4]Hitachi Energy GSA-AA: Dry RIP wall-bushing product example
Hitachi Energy
Supports: A named dry RIP design uses an oil-free core and silicone housing; its safety and mounting claims are product-specific.
- [5]IEEE C57.19.100: Guide for Application of Power Apparatus Bushings
IEEE Standards Association
Supports: Field interpretation of capacitance and power factor changes.
Selection guidance for buyers. Confirm specifications and test evidence for the quoted model and supplying entity.
