resin bushing for power transformer equipment
Overview of Resin Bushing
A resin bushing, commonly named epoxy‑resin transformer bushing, belongs to indispensable high‑voltage insulating hardware widely installed on oil‑immersed transformers, distribution switch‑gear, power‑station equipment and electrical cabinets. The core function of the resin bushing is to lead internal high‑voltage and low‑voltage copper conductors out from the grounded transformer oil tank wall. It delivers reliable electrical insulation, fixed support for live conductive rods, sealed protection against oil leakage and stable mechanical bearing capacity under long‑time power‑grid operation.
Solid cast epoxy resin serves as the main insulating medium for mainstream resin bushing products. Modified epoxy material filled with silica filler improves dielectric strength, anti‑aging performance and structural rigidity. A standard resin bushing consists of three core parts: solid copper conductive rod, one‑piece molded epoxy insulation shell, and metal mounting flange and wiring terminals. Every‑piece integrated casting structure cuts internal air gaps, lowers partial‑discharge risk and greatly improves operational stability compared with split‑type porcelain bushings.
Core Working Principle
When transformer winding current flows through the inner copper rod of the resin bushing, the thick epoxy‑resin outer layer isolates charged conductors from the metal transformer shell. Uniform electric‑field distribution inside molded resin prevents flash‑over, electric leakage and short‑circuit accidents. The sealed interface between resin shell and metal flange stops transformer oil from leaking out and blocks moisture, dust and industrial pollutants from invading the oil‑tank interior.
Main‑stream Parameter Specification Table
| Specification Item | Standard Parameter Range | Remarks |
|---|
| Rated Voltage | 1.2kV‑34kV | Cover ANSI and DIN industrial standard types |
| Rated Working Current | 55A‑315A, 630A‑6300A | Decide copper‑rod cross‑section size |
| Operating Ambient Temperature | ‑45℃ ~ +45℃ | Suitable for extreme cold and high‑temperature zones |
| Max Working Altitude | 1000m (standard), 2500m (reinforced anti‑pollution type) | High‑altitude customized resin bushing available |
| Max Inclined Installation Angle | 30 Degree | Vertical and inclined mounting supported |
| Dielectric Strength | ＞20kV/mm | Nanometer modified epoxy for high‑grade insulation |
| Partial Discharge Value | ＜5pC under rated working voltage | Critical index for long‑term service life |
Primary Material‑Based Advantages of Resin Bushing
First, outstanding insulation property. Compact cast epoxy‑resin structure keeps stable insulating performance under damp, rainy and heavily‑polluted outdoor surroundings. Second, strong mechanical performance. Resin bushing features shock‑resistance, anti‑crash capacity and lighter weight. Its weight is nearly sixty percent lower than traditional porcelain bushing with identical voltage grade, which reduces flange load on transformer tank walls. Third, great environmental adaptability. Anti‑fouling resin‑bushing surface resists industrial dust, salt fog and chemical contamination. Fourth, convenient production and customization. Manufacturers adjust copper‑rod diameter, flange size and creepage distance according to different transformer‑model demands.
Common Resin‑Bushing Classification
- Single‑phase resin bushing: Widely applied for 15kV‑34kV single‑phase distribution transformers, common rated‑current parameter 55A.
- DIN‑standard resin bushing: Follow German industrial production criteria, popular for European‑market transformer spare‑part procurement.
- ANSI‑standard resin bushing: Meet American power‑equipment specifications for North‑American distribution grids.
- Indoor‑type and outdoor‑type resin bushing: Outdoor‑grade products add anti‑ultraviolet and anti‑pollution outer coating.
Every type of resin bushing undertakes strict finished‑product inspection including high‑voltage withstand test, partial‑discharge detection, mechanical vibration test and sealing leakage test before factory delivery.
