Transformer Overhauling
Complete 11kV/33kV Core & Coil Overhaul to BUET Laboratory Standards
Comprehensive turnkey overhauling of distribution and power transformers up to 33kV / 10 MVA. Includes full coil rewinding, high-vacuum dehydration, de-sludging, gasket renewal, and factory acceptance testing.
Key Deliverables & Specifications
99.99% Electrolytic Copper Windings
Double paper-covered oxygen-free copper with Class H Nomex insulation.
High-Vacuum Thermal Dehydration
Baking active core in vacuum oven to strip moisture down to < 10 ppm.
Complete Nitrile Cork Gasket Renewal
100% replacement of all tank, bushing, and valve gaskets with oil-resistant nitrile.
BUET Laboratory FAT Testing
Complete FAT inspection certificate compliant with IEC 60076 standards.
Engineering Scope & Capabilities
Turnkey Substation Transformer Overhauling
Trafo Engineering provides complete on-site and workshop overhauling services for oil-immersed and dry-type transformers across Bangladesh. Our ISO-certified facility in Dhaka is equipped with precision coil winding machinery, high-vacuum drying chambers, and comprehensive dielectric test benches.
Why Overhauling is Critical for Industrial Transformers
Over years of continuous operation, transformer oil degrades, moisture penetrates kraft paper insulation, and thermal cycles cause core clamping bolts to loosen. Periodic comprehensive overhauling prevents catastrophic explosive failures, restores original efficiency, and extends asset lifespan by 15 to 20 years.
Our In-House Overhauling Facilities
- 15-Ton Overhead Crane Bay: Safe lifting and de-tanking of active core assemblies up to 10 MVA.
- High-Vacuum Thermal Drying Chamber: Dehydration of active core insulation to < 10 ppm moisture content at 105°C.
- Automated Copper Winding Machines: Precision layer-wound and disc-wound coils using 99.99% pure electrolytic copper.
- BUET Stamped FAT Test Bench: Ratio, polarity, vector group, winding resistance, and 80kV dielectric breakdown testing.
Step-by-Step Engineering Methodology
On-Site Diagnostic & Oil Sampling
Secondary injection, insulation resistance (Megger), and dissolved gas analysis (DGA).
De-Tanking & High-Pressure Core Washing
Lifting active core assembly, chemical neutralisation, and removal of acidic sludge.
Precision Coil Rewinding & Vacuum Baking
Rewinding damaged limbs, insulation layering, and 24-hour vacuum thermal dehydration.
Re-Tanking, Oil Re-Filling & Final FAT
Vacuum oil filling under negative pressure, seal testing, and comprehensive FAT tests.
Diagnostic & Calibration Instruments
| Testing Instrument / Apparatus | Capability & Standard Compliance |
|---|---|
| High-Vacuum Oil Plant | 6,000 LPH Double-Stage Degasser (IEC 60296) |
| 5kV Digital Megger | Megger MIT515 Diagnostic Tester (IEEE C57.12.90) |
| Turns Ratio Meter (TTR) | 3-Phase Precision Transformer Ratio Analyzer |
| Micro-Ohm Contact Meter | 100A Winding Resistance Analyzer |
Frequently Asked Technical Questions
Book Transformer Overhauling
Get an on-site engineer dispatched or receive a formal branded quotation.
Available 24 hours a day for factory power outages and emergency substation repairs.