RIP Condenser Cores: Design Inputs and Acceptance Checks
Review field grading, dimensions, impregnation, curing and model-specific dielectric tests when sourcing RIP condenser cores.
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
- 01How do capacitive aluminum foil screens equalize the electric field inside an RIP core?
- 02How do VPI and step-curing help control voids in RIP cores?
- 03What partial discharge and tan delta margins distinguish a premium RIP core?
- 04How can transformer and bushing OEMs customize RIP cores from 52 kV to 800 kV?
- 05Frequently asked questions
- 06Standards & sources
In short
Define the RIP core envelope, conductor interface, capacitance grading, thermal duty and core-level tests before integrating it into a complete bushing.
- The RIP core grades the internal electric field, while the housing and interfaces also contribute to complete-bushing insulation and mechanical performance.
- Foil-edge treatment and axial placement affect field concentration; check the approved grading design and manufacturing inspection record.
- Use the agreed impregnation and cure plan to control voids; inspect the proposed core and its dielectric measurements.
- Controlled step-curing aims to limit heat and residual stress; verify Tg and curing records for the specified core.
- Keep core acceptance separate from complete-bushing acceptance; request both sets of drawings and test records.
Core drawings and core-level test limits must be agreed separately from the complete AC bushing tests under IEC 60137.
01How do capacitive aluminum foil screens equalize the electric field inside an RIP core?
Without internal grading screens, voltage concentrates sharply near the central conductor and the grounded mounting flange. An RIP condenser core inserts dozens of coaxial aluminum foil cylinders at calculated radial thicknesses and stepped axial lengths, forming a series capacitor network that forces both the radial field through the paper-epoxy dielectric and the axial tangential field along the tapered ends to remain uniform.
Review foil position and edge treatment on the grading design, then compare the measured C1/C2 values with the approved core drawing.
02How do VPI and step-curing help control voids in RIP cores?
Vacuum drying reduces paper moisture before resin enters; impregnation and controlled curing aim to avoid unfilled spaces and internal stress in the core.
Ask for the drying, impregnation and cure records plus PD and tan delta results for the actual core.
- Deep vacuum drying: removes bound moisture in crepe paper before resin introduction.
- VPI permeation: specify resin flow and process controls intended to reduce unfilled paper regions, then assess the finished core.
- Exothermic step-cure & CNC finishing: stress-free curing followed by precision 13 m CNC lathe taper turning.
03What partial discharge and tan delta margins distinguish a premium RIP core?
No generic PD or tan delta margin defines a premium standalone core. Agree measurement conditions and core limits, then separately review the assembled bushing test results.
Core PD and tan delta measurements are useful inputs, but they do not establish compliance of the completed bushing. Agree core limits separately and request type and routine test evidence for the assembled model.
| Parameter | Applicable complete-bushing clause | Catalogue example or requested evidence |
|---|---|---|
| Rated Voltage Classes | Above 1 kV AC | 52, 72.5, 126, 145, 170, 252, 363, 550, 800 kV |
| Rated Current & Conductor | Per apparatus rating | 630 A to 5000 A (solid rod or draw-lead tube) |
| Partial Discharge at 1.05 Um/sqrt(3) | Agree by insulation type and test point | Request measured core PD at the agreed voltage and method |
| Dielectric Dissipation Factor (tan delta) | Agree voltage, temperature and limit | Request measured core value and complete-bushing report |
| Glass Transition Temperature (Tg) | Thermal class dependent | Tg >= 120 degrees C (Class E 120 C / Class B 130 C) |
| Lightning Impulse Withstand (BIL) | Per voltage class | Up to 2100 kV (for 800 kV class) |
| Switching Impulse Withstand (SIL) | Per voltage class (>= 300 kV) | Up to 1600 kV (for 550 kV & 800 kV classes) |
| Applicable Standards | Apply to complete AC bushing where relevant | Confirm each standard by assembly and contract |
“Buyer check: request core drawings and measured dielectric results, then test the completed bushing separately.”
04How can transformer and bushing OEMs customize RIP cores from 52 kV to 800 kV?
Send the core envelope, conductor and housing interfaces, voltage/current, capacitance target and thermal duty; approve a core drawing and test plan before production.
Cores can be supplied for oil-to-air, oil-to-SF6, oil-to-oil, GIS lead-out and AC/DC wall bushings, and are shipped in vacuum-sealed moisture-barrier foil with desiccant and humidity indicators, or inside sealed transport canisters, accompanied by complete C1/C2 capacitance, tan delta and PD test protocols.
Applicable EONOVA Equipment
Conclusion
Approve foil grading, material and interfaces for the core, then compare core-level measurements with the complete-bushing tests before acceptance.
Talk to an EONOVA engineerFrequently Asked Questions
How are bare RIP condenser cores protected against moisture during international shipping and storage?
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Specify sealed moisture-barrier packaging, humidity indicators where used and storage limits; inspect the seal and recheck dielectric condition before integration after long storage.
Can the quoted supplier design an RIP core to match our existing flange, porcelain/silicone housing and C1 capacitance?
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Potentially, subject to design review. Send the existing flange and housing drawings, conductor interface and C1 target; approve the matched core drawing and acceptance tests.
Why is a glass transition temperature (Tg) of at least 120 degrees C important for an RIP core?
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The resin glass-transition temperature is relevant to the core thermal margin, but one Tg value does not guarantee complete-bushing performance. Specify the operating and overload temperatures, request the measured Tg of the proposed material, and review dielectric and mechanical tests at the agreed conditions.
Standards & Sources
- [1]IEC 60137:2017: Insulated bushings for alternating voltages above 1000 V
International Electrotechnical Commission (TC 36)
Supports: Thermal stability, tan delta, partial discharge and impulse requirements for resin-impregnated paper (RIP) insulation.
- [2]IEEE C57.19.01: Standard Performance Characteristics and Dimensions for Outdoor Apparatus Bushings
IEEE Standards Association
Supports: Capacitance grading, power factor limits and BIL/SIL levels for condenser bushing cores.
- [3]CIGRE TB 755: Transformer Bushing Reliability
CIGRE Working Group A2.43
Supports: Manufacturing quality factors, moisture protection and field diagnostics for RIP condenser cores.
- [4]GB/T 4109: Insulated bushings for alternating voltages above 1000 V
Standardization Administration of China
Supports: National standard routine and type test acceptance criteria for 52 kV to 800 kV RIP cores.
Selection guidance for buyers. Confirm specifications and test evidence for the quoted model and supplying entity.
