Bushing
Product Classification & Technical Specifications
Product Series Overview
This series of bushings comprises oil-SF₆ or oil-air capacitance-graded bushings, utilizing a capacitance core grading structure to connect the transformer internal winding leads through the tank wall or switch enclosure to the external power lines. The product design fully considers transformer operating conditions, offering excellent electrical performance, mechanical strength, and sealing reliability.
|
Voltage Level |
Example Model |
Main Application Scenarios |
|
24kV Bushing |
BRDL-24/□ |
Distribution Transformers, Small Power Transformers |
|
40.5kV Bushing |
BRDL-40.5/□ |
35kV Class Power Transformers, Reactors |
|
72.5kV Bushing |
BRDLQ-72.5/□ |
66kV Class Power Transformers, High-Voltage Reactors |
|
126kV Bushing |
BRDLQ-126/□ |
110kV Class Power Transformers, Converter Transformers |
|
252kV Bushing |
BRDLW-252/□ |
220kV Class Power Transformers, Interconnecting Transformers |
24kV Bushing
Product Description:
Suitable for 24kV class distribution transformers and small power transformers. Features epoxy resin impregnated paper (RIP) or oil-impregnated paper (OIP) capacitance cores with porcelain or composite silicone rubber external insulation. Compact structure for easy installation and maintenance.
Technical Parameters:
|
Parameter |
Standard Parameters |
Remarks |
|
Rated Voltage (Um) |
24 kV |
— |
|
Rated Current |
400-2000 A |
Based on design requirements |
|
Rated Insulation Level |
LI/AC: 125/55 kV |
Lightning impulse / Power frequency withstand |
|
Creepage Distance |
Based on pollution level |
Class II/III/IV optional |
|
Medium Type |
Oil-Air, Oil-SF₆, Oil-Oil |
Based on installation environment |
|
Insulation Type |
OIP / RIP |
— |
|
Applicable Standards |
IEC 60137, GB/T 4109 |
— |
Material & Appearance:
● External Insulation: High-strength electrical porcelain (brown/white) or silicone rubber composite housing (grey)
● Capacitance Core: Epoxy Resin Impregnated Paper (RIP) or Oil-Impregnated Paper (OIP)
● Flange: Aluminum alloy or stainless steel, anti-corrosion treated
● Grading Shield: Aluminum alloy, anodized surface
● Installation Method: Vertical or angled mounting on turret
40.5kV Bushing
Product Description:
Suitable for 35kV class power transformers, reactors, and high-voltage switchgear. Available with OIP or RIP capacitance core structure, porcelain or composite housing, meeting various pollution level requirements.
Technical Parameters:
|
Parameter |
Standard Parameters |
Remarks |
|
Rated Voltage (Um) |
40.5 kV |
— |
|
Rated Current |
400-3150 A |
Based on design requirements |
|
Rated Insulation Level |
LI/AC: 200/95 kV |
Lightning impulse / Power frequency withstand |
|
Creepage Distance |
≥900 mm (Class III) |
Higher pollution level available |
|
Medium Type |
Oil-Air, Oil-SF₆ |
— |
|
Insulation Type |
OIP / RIP |
— |
|
Partial Discharge |
≤5 pC (at 1.5Um/√3) |
100% factory tested |
Features & Advantages:
● Mature OIP Technology: Decades of operational experience, high reliability
● RIP Technology Option: Maintenance-free, no oil leakage risk
● Sealing Structure: Double-seal design ensures long-term leak-free operation
● Seismic Performance: Passed 0.5g acceleration seismic test
72.5kV Bushing
Product Description:
Suitable for 66kV class power transformers and high-voltage reactors. Uses OIP capacitance core with optimized grading structure for higher voltage levels, ensuring uniform electric field distribution. Porcelain housing features large and small shed design for superior pollution resistance.
Technical Parameters:
|
Parameter |
Standard Parameters |
Remarks |
|
Rated Voltage (Um) |
72.5 kV |
— |
|
Rated Current |
630-4000 A |
Based on design requirements |
|
Rated Insulation Level |
LI/AC: 350/160 kV |
Lightning impulse / Power frequency withstand |
|
Creepage Distance |
≥1800 mm (Class III) |
Class IV optional |
|
Medium Type |
Oil-Air, Oil-SF₆ |
— |
|
Capacitance Core |
OIP |
High vacuum impregnation process |
|
Capacitance Value |
Matched per design |
For voltage tapping |
|
Applicable Standards |
IEC 60137, GB/T 4109 |
— |
Material & Appearance:
● Porcelain Housing: High-strength electrical porcelain, bending strength ≥120MPa
● Center Conductor: High-conductivity copper rod or tube
● Oil Conservator: Stainless steel with oil level sight glass
● Tap: Optional voltage tapping device or bushing CT
126kV Bushing
Product Description:
Suitable for 110kV class power transformers, converter transformers, and shunt reactors. Uses OIP capacitance core with optimized capacitive screen design ensuring uniform radial and axial electric field distribution. Can be configured for SF₆ duct or air-side installation.
Technical Parameters:
|
Parameter |
Standard Parameters |
Remarks |
|
Rated Voltage (Um) |
126 kV |
— |
|
Rated Current |
630-5000 A |
Based on design requirements |
|
Rated Insulation Level |
LI/AC: 550/230 kV |
Lightning impulse / Power frequency withstand |
|
Creepage Distance |
≥3150 mm (Class III) |
Class IV ≥4000mm optional |
|
Medium Type |
Oil-Air, Oil-SF₆ |
— |
|
Capacitance Core |
OIP |
Number of capacitive screens ≥12 |
|
Partial Discharge |
≤5 pC (at 1.5Um/√3) |
100% factory tested |
|
tanδ |
≤0.005 (at 20°C) |
— |
|
Bending Load |
≥2000 N |
Safety factor ≥2.5 |
|
Applicable Standards |
IEC 60137, GB/T 4109 |
— |
Features & Advantages:
● High Vacuum Impregnation Process: Ensures void-free core, excellent PD performance
● Sealing Reliability: Double seal + explosion-proof membrane structure for safe operation
● Grading Ball Design: Optimizes oil-side electric field, prevents partial discharge
● Seismic Performance: Verified by 0.5g acceleration seismic test
Design Customization:
● Installation Angle: 0°-60° adjustable
● Tap Configuration: Optional voltage tapping device, bushing CT mounting seat
● Oil Conservator Type: Conventional / Corrugated expansion type
● External Insulation: Porcelain / Composite housing optional
252kV Bushing
Product Description:
Suitable for 220kV class large power transformers, interconnecting transformers, and converter transformers. Uses OIP capacitance core with multiple capacitive screens and precise grading design, meeting stringent requirements for partial discharge and dielectric loss in ultra-high voltage grids.
Technical Parameters:
|
Parameter |
Standard Parameters |
Remarks |
|
Rated Voltage (Um) |
252 kV |
— |
|
Rated Current |
800-6300 A |
Based on design requirements |
|
Rated Insulation Level |
LI/AC: 1050/460 kV |
Lightning impulse / Power frequency withstand |
|
Creepage Distance |
≥6300 mm (Class III) |
Class IV ≥8000mm optional |
|
Medium Type |
Oil-Air, Oil-SF₆ |
— |
|
Capacitance Core |
OIP |
Number of capacitive screens ≥24 |
|
Partial Discharge |
≤5 pC (at 1.5Um/√3) |
100% factory tested |
|
tanδ |
≤0.005 (at 20°C) |
— |
|
Bending Load |
≥4000 N |
Safety factor ≥2.5 |
|
SF₆ Interface |
Optional |
For GIS/GIL connection |
|
Applicable Standards |
IEC 60137, GB/T 4109 |
— |
Material & Appearance:
● Capacitance Core: High-quality cable paper + aluminum foil screens, high vacuum impregnated
● Porcelain Housing: High-strength porcelain, single/multi-section structure
● Grading Ring: Aluminum alloy, large diameter design for optimal electric field
● Oil Conservator: Stainless steel corrugated expander, fully sealed structure
● Tap: Optional outer screen grounding / voltage tapping
Features & Advantages:
● Low Partial Discharge: ≤5 pC at 1.5Um/√3, exceeding standard requirements
● Low Dielectric Loss: tanδ ≤0.005, stable long-term operation
● High Mechanical Strength: Withstands short-circuit electromagnetic forces, wind, and seismic loads
● Sealing Life: Double seal design, expected lifespan ≥30 years
● Maintenance-Free Design: No maintenance required for oil-side and air-side
Manufacturing Process & Quality Assurance
Production Process Flow
|
Process |
Key Control Points |
In-Line Inspection |
|
Capacitance Core Winding |
Constant temperature/humidity environment, automatic tension control, aluminum foil positioning accuracy ±0.5mm |
Capacitance online monitoring |
|
Vacuum Drying |
Temperature 115-125°C, vacuum ≤10Pa, duration ≥72h |
Dew point, vacuum record |
|
Oil Impregnation |
High-purity transformer oil, impregnation temperature 85-95°C, pressure cycling |
Moisture content, gas content detection |
|
Assembly |
Porcelain cleaning/drying, gasket compression control, torque management |
Seal test |
|
Factory Testing |
Full test items, 100% qualified |
Test report archived |
Quality Inspection System
Incoming Quality Control (IQC)
Porcelain Parts: Dimensions, appearance, ultrasonic inspection
Insulating Paper / Aluminum Foil: Thickness, tensile strength, dielectric properties
Transformer Oil: Moisture content, breakdown voltage, dielectric loss, gas content
Seals: Hardness, compression set, oil resistance
In-Process Quality Control (IPQC)
Capacitance Core: Capacitance deviation, inter-screen insulation, appearance
Vacuum Drying: Dew point, vacuum, time curve record
Impregnation: Temperature, pressure, time record
Outgoing Quality Control (OQC): 100% performed on each bushing
Insulation Resistance Measurement
Dielectric Loss Factor (tanδ) and Capacitance Measurement
Power Frequency Withstand Voltage Test
Partial Discharge Measurement (at 1.5Um/√3)
Seal Test (Air pressure / Oil pressure)
Voltage Tapping Device Test (if applicable)
Type Testing: Performed during design finalization or standard updates
Lightning Impulse Voltage Test
Switching Impulse Voltage Test (for 252kV class)
Temperature Rise Test
Short-Time Current Test
Bending Load Test
Seismic Test
Artificial Pollution Test
Radio Interference Voltage Test
Quality Commitment
Standard Compliance
Committed to 100% compliance with applicable IEC 60137, GB/T 4109, and other standards.
01
Traceability
Each bushing has a unique serial number traceable to raw material batch, production machine, and operator.
02
Warranty Period
24 months from commissioning or 30 months from delivery (whichever comes first).
03
Failure Commitment
During warranty, unconditional replacement for failures caused by material or workmanship defects, covering resulting direct losses.
04
Response Mechanism
24-hour rapid response for quality issues, 48-hour on-site support (domestic).
05
Product Certifications
|
Certification |
Standard/Organization |
Scope |
|
Quality Management System |
ISO 9001:2015 |
All Series |
|
Environmental Management System |
ISO 14001:2015 |
All Series |
|
Occupational Health & Safety |
ISO 45001:2018 |
All Series |
|
International Standard |
IEC 60137 |
All Series |
|
National Standard |
GB/T 4109 |
All Series |
|
Laboratory Accreditation |
CNAS |
Type Test Capability |
|
Grid Qualification |
State Grid / China Southern Grid |
All Series |
Customization Capability & Technical Development (OEM/ODM)
Technical Design Support
Electric Field Simulation
Uses finite element analysis to optimize capacitive screen structure, ensuring uniform electric field distribution.
Thermal Analysis
Optimizes conductor cross-section and heat dissipation structure based on rated current and load characteristics.
Seismic Calculation
Verifies mechanical strength based on local seismic intensity.
Interface Matching
Customizes mounting flange based on transformer turret or switchgear interface dimensions.
Product Customization Options
|
Customization Dimension |
Options |
|
Voltage Level |
24kV – 252kV full series, extendable to 363kV/550kV |
|
Rated Current |
400A – 6300A, higher currents negotiable |
|
External Insulation Material |
Electrical porcelain (brown/white), silicone rubber composite housing |
|
Pollution Level |
Class II (light), Class III (heavy), Class IV (very heavy) |
|
Creepage Distance |
Calculated per pollution level, can exceed standard requirements |
|
Installation Angle |
0°, 15°, 30°, 45°, 60° vertical/angled |
|
Medium Type |
Oil-Air, Oil-SF₆, Oil-Oil |
|
Tap Configuration |
Outer screen grounding, voltage tapping, bushing CT mounting seat |
|
Oil Conservator Type |
Conventional conservator, metal corrugated expander |
|
Grading Ring |
Single ring / double ring, diameter designed per voltage level |
|
Color |
Porcelain natural, silicone rubber grey/red/custom |
Sample Support
Sample Policy
Supports prototype manufacturing for new products/voltage levels for type test validation.
Sample Lead Time
30-45 days for 24-72.5kV class; 60-90 days for 126-252kV class.
Sample Cost
Negotiable based on development complexity; partial or full mold fee refundable upon bulk order.
Project Execution & Full Lifecycle Services
Packaging Solutions
|
Packaging Type |
Application |
Technical Description |
|
Standard Packaging |
Domestic transport, general warehousing |
Wooden/steel crate + vibration support + moisture cover, horizontal/vertical fixation |
|
Export Packaging |
Sea freight, long-distance transport |
Fumigated wooden crate + vacuum moisture-proof packaging + shock recorder |
|
Bulk Packaging |
Multiple units same shipment |
Separate compartments, collision protection |
|
On-Site Packaging |
Special dimensions |
Engineer on-site measurement, custom packaging plan |
Labeling Information: Each crate includes label with: product model, serial number, voltage level, current, net/gross weight, center of gravity, lifting points, anti-tilt marking.
Logistics & Transport
Transport Requirements
Bushings must remain upright (or specified angle), avoid severe vibration.
Partners
Professional heavy transport companies with transformer bushing transport experience.
Transport Modes
Flatbed truck (road), open-top/flat rack container (sea), air freight (urgent).
Insurance
Full value all-risk insurance (including vibration and tilt damage).
Tracking
Shock recorder installed; data read upon arrival to verify transport status.
Site Acceptance
Guidance provided for unpacking inspection; sign off after confirming appearance integrity.
Installation & Commissioning
For transformer bushing installation, the following technical support is provided:
Pre-Installation Preparation
Installation environment check (cleanliness, temperature, humidity)
Unpacking acceptance guidance (visual inspection, accessory verification)
Installation tool recommendations (special lifting tools, torque wrench)
Installation Process Guidance
Lifting Guidance: Lifting point selection, lifting angle, collision prevention measures
Assembly Guidance: Seal installation, thread tightening torque, grading ring installation
Tap Connection: Outer screen grounding or voltage tapping device wiring
Oil / SF₆ Filling: Oil level adjustment, SF₆ pressure setting
Post-Installation Checks
Visual inspection
Insulation resistance test
Seal check
Partial discharge re-measurement (if necessary)
Training
Training Modules:
|
Training Topic |
Key Content |
Format |
|
Product Structure & Principles |
Capacitance core structure, grading principle, seal design |
On-site/Video/Manual |
|
Installation Process Specifications |
Lifting, assembly, wiring, oil/SF₆ filling |
On-site demo + Manual |
|
Operation & Maintenance |
Inspection points, oil level observation, PD monitoring, infrared thermography |
On-site/Manual |
|
Fault Identification & Handling |
Common fault symptoms, cause analysis, emergency measures |
Case study + Manual |
|
Spare Parts Management |
Seal storage, tap protection, conservator maintenance |
On-site/Manual |
Training Materials: Provided with "Bushing Installation, Operation & Maintenance Manual," "Product Certificate," and "Factory Test Report."
After-Sales Service
Service Channels
400 technical hotline + WeChat service group + email support.
Response Time
Consultation response within 2 hours; quality issue handling process initiated within 24 hours.
Service Records
Written report provided for each service, signed by customer.
Quality Follow-Up
Regular follow-up visits to monitor operational status.
Maintenance Guidance
In-Service Maintenance:
- Inspection Cycle: Visual inspection monthly, infrared thermography semi-annually recommended.
- Inspection Content: Porcelain/composite housing appearance, oil level indication, tap grounding wire, grading ring.
- PD Monitoring: Energized PD detection recommended annually (for 126kV and above).
Anomaly Handling:
- Abnormal Oil Level: Determine cause, top up with same type oil, or replace conservator.
- Oil Leakage: Tighten bolts or replace seals (requires outage).
- Excessive PD: Analyze cause, schedule outage inspection or replacement.
- Porcelain Damage: Assess damage level, arrange replacement.
Spare Parts Support
The following spare parts are available:
|
Part Category |
Specification |
Recommended Stock |
|
Seals/Gaskets |
OEM material (Nitrile/Fluororubber) |
2-3 sets per model |
|
Tap Protection Device |
Outer screen grounding tab, moisture cap |
1-2 sets per model |
|
Grading Ring |
Matching specification |
Can be shared |
|
Oil Level Gauge |
Matching model |
1-2 units |
|
Drain Valve/Plug |
Matching specification |
2-3 units |
|
Connection Bolts/Nuts |
Stainless steel |
Quantity as needed |
|
Desiccant |
For conservator |
Periodic replacement |
|
Special Tools |
Tap wrench, seal installation tool |
Optional |
|
Identical Spare Bushing |
Full voltage range |
Recommended for critical substations |
Power Systems
● Power Transformers: Generator step-up transformers, substation main transformers, distribution transformers
● Converter Transformers: HVDC converter stations
● Interconnecting Transformers: Grid interconnection between different voltage levels
● Shunt Reactors: Reactive power compensation for EHV/UHV lines
Industrial Electrical
● Rectifier Transformers: Metallurgical, chemical industries
● Furnace Transformers: Smelting industry
● Mining Transformers: Underground / surface mine substations
New Energy
● Wind Farm Step-Up Transformers: Wind power collection station main transformers
● PV Step-Up Transformers: Solar power station main transformers
● Energy Storage Substations: Energy storage station main transformers
Rail Transit
● Traction Transformers: Railway traction substations
● Power Transformers: Subway / light rail power supply systems
High-Voltage Switchgear
● GIS/GIL: Connection to SF₆ ducts
● High-Voltage Wall Bushings: Substation wall penetrations
Business Cooperation Models
1. Pricing Mechanism
Pricing Model
Quoted based on voltage level, rated current, insulation level, and pollution level.
Quotation Composition
Raw material cost + processing fee + testing fee + packaging & transport fee.
Volume Discount
Tiered pricing for multiple units in same batch.
Quotation Validity
30 days (re-confirmed during significant raw material price fluctuations).
2. Payment Terms
|
Transaction Type |
Terms |
Applicable Scope |
|
T/T |
30% advance + 70% before shipment |
Regular orders |
|
L/C |
Irrevocable L/C at sight / usance |
Export orders, high-value orders |
|
Installment |
Advance + delivery + warranty retention |
Large engineering projects |
|
Western Union |
100% prepayment |
Small spare parts orders |
3. Distribution & Partnership Policy
Partners:
Transformer manufacturer supply channels
Power engineering EPC contractors
Power equipment importers/exporters
Grid system operation & maintenance units
Support for Partners:
|
Support Type |
Description |
Support Type |
|
Territory Protection |
Exclusive/core agent authorization, strict regional division |
Territory Protection |
|
Project Registration |
Key project registration system to avoid channel conflict |
Project Registration |
|
Technical Support |
Free technical training, assistance with bid document preparation |
Technical Support |
|
Pricing Support |
Exclusive agent pricing, special bid support |
Pricing Support |
|
Marketing Support |
Samples, catalogs, demo materials, joint exhibition participation |
Marketing Support |
|
After-Sales Support |
Partner service team training, joint after-sales response |
After-Sales Support |
FAQ – Common Technical Questions
Q: How to select creepage distance based on pollution level?
A: According to IEC 60137, the relationship between pollution level and minimum creepage distance is:
Class I (Light): 16 mm/kV
Class II (Medium): 20 mm/kV
Class III (Heavy): 25 mm/kV
Class IV (Very Heavy): 31 mm/kV
Where kV refers to the highest voltage Um. For example, a 126kV bushing for Class III pollution requires minimum creepage distance = 126 × 25 = 3150mm. Our company can provide designs with higher creepage distance upon request.
Q: What are the main differences between OIP and RIP bushings? How to choose?
A: OIP (Oil-Impregnated Paper) Bushing: Traditional technology with oil-impregnated paper core; requires oil conservator; oil level needs monitoring during operation. Advantages: Extensive operational experience, relatively lower cost.
RIP (Resin-Impregnated Paper) Bushing: Dry-type technology with epoxy resin-impregnated paper core; no oil conservator; maintenance-free. Advantages: No oil leakage risk, flexible installation angles.
Recommendation: Conventional transformers may choose OIP (cost advantage); maintenance-free, angled installation, or harsh environments may favor RIP.
Q: What should be considered during bushing transport and storage?
A: 1. Keep Upright: Bushings must be stored vertically (or at specified angle); never lay flat or invert.
2. Moisture & Dust Protection: Packaged bushings should be stored in clean, dry environments, protected from sun and rain.
3. Prevent Vibration: Avoid severe vibration and shock during transport.
4. Oil Level Check: Regularly check oil level of OIP bushings during storage.
5. Storage Duration: Recommended ≤1 year; beyond this, electrical tests should be repeated.
Q: What is the required compression for seals during bushing installation?
A: Seal compression should be controlled between 15% and 25%. Insufficient compression leads to poor sealing; excessive compression causes permanent deformation and seal failure. Our company provides special installation tools and torque requirements. Torque wrenches should be used to tighten flange bolts in sequence to ensure uniform compression.
Q: Causes and handling of excessive partial discharge in bushings?
A: Possible causes:
1. Core moisture ingress during installation
2. Gas discharge between capacitive screens
3. Poor tap contact
4. Improper grading ball installation
Handling: First determine the PD source. If core-related, return to factory for processing. If installation-related (tap, grading ball), can be handled on-site. Our company provides on-site PD detection and diagnostic services.
Q: What is the function of the bushing outer screen tap? What should be noted during operation?
A: Outer screen tap functions:
1. Measure bushing dielectric loss and capacitance (preventive testing)
2. Extract voltage signal (voltage tapping device)
3. Ground the outer screen of the capacitance core
Operational notes: Outer screen must be reliably grounded (directly or via protector). Must never be open-circuited during operation, as this could generate high voltage and damage insulation. When disconnecting for maintenance, short-circuit the tap after removing the ground.
Q: Have your bushings passed seismic testing?
A: Yes, our 126kV and above bushings have passed seismic tests at 0.5g acceleration (equivalent to seismic intensity IX). For high seismic intensity areas (e.g., above 0.4g), we can perform specialized seismic calculations and testing to provide reinforced designs meeting requirements.
Q: Do you provide on-site installation guidance services?
A: Yes, for 126kV and above bushings or critical projects, we provide on-site installation guidance by engineers. This includes: unpacking acceptance, lifting guidance, installation process supervision, sealing handling, oil/SF₆ filling guidance, and post-installation test witnessing. This ensures installation quality meets technical requirements.
Q: What is the service life of a bushing? What maintenance is required during operation?
A: Under normal operating conditions, bushing design life is ≥30 years.
In-service maintenance:
Routine Inspection: Appearance, oil level, abnormal noise, discharge
Periodic Testing: Preventive tests (insulation resistance, tanδ, capacitance) recommended every 3-5 years
Infrared Thermography: Annual check for contact heating
Tap Inspection: Verify reliable outer screen grounding
Seal Inspection: Check for oil leaks
Q: Can bushings of different brands be replaced for aging transformers? How to match installation interfaces?
A: Yes, we provide retrofit replacement solutions:
1. Provide original bushing installation dimensions or on-site measurement
2. Customize adapter flanges or connection bars based on original interface dimensions (flange bolt circle, center conductor specification)
3. Maintain same electrical interfaces (tap location, voltage level) as original bushing
4. Provide full installation accessories and guidance
We have successful replacement experience for aging bushings from multiple brands.
Document Version: V1.0 (High-Voltage Electrical Equipment Technical Documentation)
Basis: IEC 60137, GB/T 4109, IEEE C57.19.00
Date: May 2024
Note: The content on this page is technical description. Specific product parameters are subject to the finalized technical agreement.
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