Manufacturing Process, Quality‑Control Standard and Main Industrial Application of Resin Bushing
Basic Definition
Resin bushing, also known as epoxy‑resin high‑voltage transformer bushing, is a solid‑type penetrating insulator manufactured through high‑temperature epoxy casting, copper‑rod precise machining, flange assembly and multi‑round electrical performance testing. It runs as the essential connecting component linking transformer internal winding conductors and external power cables. Every production procedure decides the final insulation performance and service lifespan of finished resin bushing.
Complete Production Workflow Breakdown
Step 1: Raw‑material screening. Producers select high‑purity oxygen‑free copper rod for conductive core and low‑viscosity modified epoxy resin mixed with silica‑based inorganic filler. Raw‑material inspection checks copper‑rod conductivity, epoxy curing speed, heat‑resistance index and anti‑aging parameter. Unqualified raw materials will be rejected to prevent batch‑product failure.
Step 2: Precision processing for copper conductor rod. Workers cut, polish, thread and shape wiring terminals for copper rods according to rated‑current specifications. Larger‑current resin bushing needs thicker copper cross‑section to avoid over‑heating under long‑time load.
Step3: Mold casting and high‑temperature curing. Staff place the processed copper rod inside sealed metal mould, inject liquid epoxy resin under vacuum environment to exhaust inner air bubbles. Vacuum‑casting technology eliminates tiny air pockets which are the major cause of partial discharge. Then the mould enters constant‑temperature oven for staged heating curing and solid‑forming.
Step4: Post‑processing and surface treatment. Demold finished resin shell, polish outer insulating surface and spray anti‑ultraviolet protective coating for outdoor‑use resin bushing. Metal mounting flange and sealing rubber rings are assembled afterwards.
Step5: Multi‑dimensional factory quality inspection. The testing checklist covers high‑voltage withstand test, partial‑discharge detection, temperature‑rise experiment, mechanical shock test, installation‑angle adaptability inspection and oil‑sealing leakage test. Only products passing all testing projects can leave the factory.
Resin‑Bushing Industry‑Wide Quality‑Standard Table
| Testing Item | Qualified Standard |
|---|
| Power Frequency Withstand Voltage | No breakdown and flash‑over under specified high‑voltage value |
| Partial Discharge Quantity | ＜5pC under 1.2 times rated‑voltage load |
| Temperature‑Rise Limit | Conductor temperature rise less than 65K under rated current |
| Sealing‑Performance Test | Zero oil leakage under transformer‑oil pressure environment |
| High‑Altitude Adaptation | Insulation property remains stable under 2500‑meter altitude simulation |
| Anti‑Pollution Grade | Meet outdoor anti‑fouling standard for heavy‑pollution industrial districts |
Wide‑range Application Fields for Resin Bushing
- Oil‑immersed power and distribution transformer: The most‑common application scenario. DIN‑type and ANSI‑type resin bushing serve as high‑voltage lead‑out fitting for different‑standard transformers. Single‑phase 15‑34kV, 55A resin bushing fits single‑phase household distribution transformers. 35kV, 315A heavy‑current resin bushing applies for large‑scale main transformers.
- High‑voltage switch‑gear and vacuum circuit‑breaker cabinet: Indoor‑type compact resin bushing realizes conductor penetration for switch‑gear panels.
- Substation auxiliary power equipment, mining power‑supply devices, new‑energy wind‑power and solar‑power station transformers.
- Industrial electrical equipment for chemical plants, ports, coastal engineering and heavy‑pollution factories.
Strict quality control throughout the whole manufacturing chain helps qualified resin bushing reach 20‑30‑year service life under normal‑condition power‑grid operation.
