Epoxy Resin Bushing: Definition, Types, Technical Specifications, Advantages and Application Guide
Introduction
Epoxy resin bushings are solid‑insulation electrical components constructed from high‑performance epoxy resin composite materials, widely deployed for dry‑type and oil‑immersed transformers, switchgear and power distribution equipment. Unlike traditional porcelain‑type transformer bushings, epoxy resin bushings adopt cast epoxy resin as the main dielectric medium, delivering mechanical strength, insulation performance and anti‑pollution capacity in one integrated unit.
Two mainstream epoxy resin bushing families are commonly found across power‑system projects: low‑voltage 1 kV dry‑type epoxy resin bushings with current ratings ranging from 1000 A up to 3150 A, and medium‑voltage 35 kV dry‑type epoxy resin bushings rated at 315 A. These components enable live conductors to pass safely through grounded metal tank walls of transformers, providing reliable electrical isolation and mechanical connection points for external circuit terminals.
Even though epoxy resin bushings are classified as auxiliary power accessories, their operational performance directly impacts transformer uptime. Poor‑quality epoxy bushings may produce partial discharge, surface tracking, mechanical cracking or sealing defects, which can further trigger transformer faults and unplanned power outages. This technical guide explains working features, product classifications, core benefits, application scenarios, selection tips and maintenance best‑practice for epoxy resin bushings, targeting substation engineers, procurement officers and field maintenance specialists.
Working Principle of Epoxy Resin Bushing
An epoxy resin bushing forms a rigid insulated barrier for current‑carrying metal conductors passing through grounded equipment enclosures. The high‑strength cast epoxy resin body separates live metal parts from the earthed transformer tank. The internal metal conductor transmits continuous load current, while the epoxy resin body bears all dielectric stress between live parts and ground potential.
For 1 kV epoxy resin bushings, compact solid‑cast structures are used for low‑voltage heavy‑current working conditions, focusing on thermal performance and mechanical terminal connection strength. For 35 kV epoxy resin bushings, optimized shed profiles are molded directly into the epoxy housing. These external sheds increase creepage distance, improve pollution‑flashover resistance for outdoor and heavily‑polluted substation environments.
Two primary flange mounting configurations exist for 35 kV epoxy resin bushings: pressure‑plate flange (P type) and resin flange (S type). Both designs complete mechanical fixation to transformer tank covers while maintaining structural stability. Conductive rod connection adopts external thread (W) design to facilitate fast assembly with external busbar connectors.
Main Product Classifications
Epoxy resin bushings can be grouped by rated voltage, current rating and mounting structure.
1 kV Dry‑Type Epoxy Resin Bushing (1000A‑3150A)Low‑voltage heavy‑current epoxy resin bushing series, designed for 1 kV class transformer equipment. Current grades cover 1000 A, 1600 A, 2000 A and 3150 A. Two terminal angle options are available: 90° and 0° terminal angle to match different busbar layout requirements on‑site. Square‑shaped mounting flange structure fits tank cover opening dimensions for low‑voltage transformer compartments. Mainly used for low‑voltage side outlet of oil‑immersed and dry‑type distribution transformers.
35 kV Dry‑Type Epoxy Resin Bushing (315A)Medium‑voltage epoxy resin bushing for 35 kV power transformers, rated current 315 A. Multiple overall height variants are available to satisfy different insulation and creepage requirements. Two mounting flange types: pressure‑plate flange (P) and resin integrated flange (S). Shed quantity and creepage distance are optimized for medium‑voltage outdoor substation conditions. Suitable for 35 kV oil‑immersed power transformers, and can be adapted for moderately polluted outdoor environments.
Core Advantages of Epoxy Resin Bushing
Typical Application Scenarios
‑ Low‑voltage side outlets for oil‑immersed distribution transformers (1 kV series, 1000A‑3150A)‑ 35 kV oil‑immersed power transformers for urban and rural substations‑ Dry‑type transformer high‑voltage and low‑voltage through‑wall insulation‑ Industrial plant power‑supply transformer projects‑ Wind and photovoltaic power station step‑up transformers‑ Equipment renovation and spare‑part replacement for existing transformer fleets‑ Indoor and outdoor locations with moderate industrial dust and humidity pollution
Table 1: 1 kV Dry‑Type Epoxy Resin Bushing (1000A‑3150A)
| Code 代号 | Model 型号 | H | h 2
| h3 | d | d1 | d3 | d4 | B1×B2 | t | B3×B4 | t1 | c1×c2 | d0 箱盖开孔 | creep distance 爬距 | terminal angle 端子角度 | weight (kg) 重量 |
|---|
| XD.GSTG.02.A | BFG‑1KV/1000A | 267 | 111 | 78 | 30 | 55 | 55 | 26 | 80×80 | 10 | 22×26 | 10 | 80×80 | 57 | 35 | 90° | 2 |
| XD.GSTG.02.B | BFG‑1KV/1000A | 267 | 111 | 78 | 30 | 55 | 55 | 26 | 80×80 | 10 | 22×26 | 10 | 80×80 | 57 | 35 | 0° | 2 |
| XD.GSTG.03.A | BFG‑1KV/1600A | 267 | 111 | 78 | 36 | 70 | 70 | 26 | 80×80 | 12 | 22×26 | 12 | 80×80 | 57 | 35 | 90° | 2.6 |
| XD.GSTG.03.B | BFG‑1KV/1600A | 267 | 111 | 78 | 36 | 70 | 70 | 26 | 80×80 | 12 | 22×26 | 12 | 80×80 | 57 | 35 | 0° | 2.6 |
| XD.GSTG.04.A | BFG‑1KV/2000A | 287 | 111 | 78 | 42 | 70 | 70 | 31 | 100×100 | 12 | 22×26 | 15 | 80×80 | 72 | 40 | 90° | 3.5 |
| XD.GSTG.04.B | BFG‑1KV/2000A | 287 | 111 | 78 | 42 | 70 | 70 | 31 | 100×100 | 12 | 22×26 | 15 | 80×80 | 72 | 40 | 0° | 3.5 |
| XD.GSTG.05.A | BFG‑1KV/3150A | 287 | 111 | 78 | 48 | 70 | 70 | 31 | 100×100 | 16 | 22×26 | 20 | 80×80 | 72 | 40 | 90° | 4.5 |
| XD.GSTG.05.B | BFG‑1KV/3150A | 287 | 111 | 78 | 48 | 70 | 70 | 31 | 100×100 | 16 | 22×26 | 20 | 80×80 | 72 | 40 | 0° | 4.5 |
Notes: Custom dimensions are available on request; overall H height can be adjusted according to project requirements.
Table 2: 35 kV Dry‑Type Epoxy Resin Bushing (315A)
| Sequence Number 序号 | Code 代号 | Model 型号 | H | h2 | h3 | Md | d1 | d2 | d3 | d0 箱盖开孔 | h1 干弧距离 arcing distance | creep distance 爬距 | shield 伞形 | conductive rod mode 导电杆方式 | flange mode 法兰安装方式 | view 视图 | weight (kg) 重 量 |
|---|
| 1 | XD.GSTG.35.001 | BFGM‑35KV/315A | 580 | 122 | 40 | M12*1.75 | 145 | 180 | 90 | 105 | 365 | 1256 | 8 大 9 小 | W | P | 图 1 | 9.5 |
| 2 | XD.GSTG.35.002 | BFGM‑35KV/315A | 660 | 122 | 40 | M12*1.75 | 145 | 180 | 90 | 105 | 445 | 1530 | 10 大 11 小 | W | P | 图 1 | 10.9 |
| 3 | XD.GSTG.35.003 | BFGM‑35KV/315A | 610 | 140 | 40 | M12*1.75 | 142.5 | 210 | 100 | 105 | 400 | 1440 | 9 大 9 小 | W | S | 图 2 | 11.5 |
| 4 | XD.GSTG.35.004 | BFGM‑35KV/315A | 610 | 130 | 40 | M12*1.75 | 146 | 240 | 100 | 105 | 410 | 1400 | 8 大 8 小 | W | S | 图 3 | 13 |
- Mounting mode P = Pressure‑plate flange; S = Resin flange; Conductive rod mode W = External thread.
- All data represents standard industry reference specifications.
Selection Criteria for Epoxy Resin Bushing
- Rated Voltage and Rated Current: Match bushing voltage class and current rating to transformer nominal parameters. For low‑voltage transformer outlets, select 1 kV epoxy resin bushing from 1000 A‑3150 A; for 35 kV transformer terminals, adopt 35 kV / 315 A epoxy resin bushing.
- Terminal Angle (1 kV models): Choose 0° or 90° terminal angle according to physical busbar layout on‑site to avoid installation interference.
- Mounting Flange Type: For 35 kV applications, decide between pressure‑plate flange (P) or resin‑integrated flange (S), verify tank‑cover opening dimension d0 before ordering.
- Creepage and Dry‑arc Distance: Evaluate site pollution grade; pick suitable shed profile and creepage distance for industrial or coastal polluted locations.
- Overall Dimension Constraints: Confirm total height H and surrounding clearance space inside transformer compartment. Custom height modification is supported for special‑purpose units.
- Standard Compliance: Verify products conform to relevant IEC and national power‑equipment standards for transformer bushings.
Installation & Maintenance Guidance
Pre‑installation Inspection
- Visually examine epoxy resin surface. Reject units with cracks, chipping, scratches or tracking damage on casting body and sheds.
- Check all dimensional parameters against drawing requirements: flange hole positions, thread size, terminal dimensions and tank‑cover opening compatibility.
- Confirm factory test reports including power‑frequency withstand voltage, impulse voltage and partial‑discharge test records.
Installation Notes
‑ Apply uniform torque for flange fastening bolts. Excessive torque will crack epoxy resin housing; insufficient torque causes sealing gaps.‑ Keep sufficient phase‑to‑phase and phase‑to‑ground electrical clearances. Prevent hard mechanical impact against epoxy sheds during lifting and assembly.‑ For 1 kV bushing terminals, properly fasten busbar connection bolts to avoid over‑heating points caused by loose contact.
Routine Maintenance
‑ Carry out visual inspection every 6‑12 months. Check epoxy surface for dirt accumulation, tracking, micro‑cracks. Clean shed surfaces for heavily polluted operating sites.‑ Inspect flange joints for air leakage signs, verify terminal connection torque.‑ Implement preventive electrical tests periodically: insulation resistance and partial‑discharge measurement.
‑ All maintenance tasks must be completed with transformer fully de‑energized. Do not disassemble epoxy resin bushing internal components in field conditions.
Conclusion
Epoxy resin bushings serve as robust dry‑type insulating through‑wall components for modern power transformers. The 1 kV heavy‑current series (1000A‑3150A) solves low‑voltage outlet requirements for distribution transformers, while the 35 kV / 315A series provides medium‑voltage insulation with two alternative flange mounting structures. Thanks to high mechanical strength, anti‑pollution shed design, oil‑free dry‑type construction and flexible dimensional options, epoxy resin bushings are widely adopted across utility substations, industrial power systems and renewable‑energy transformer projects. Reasonable model selection, standardized installation and periodic inspection help to minimize bushing‑related failures and safeguard long‑term transformer system reliability.
