Huanghua Group Co., Ltd. 
Transformer Winding Workshop
Company transformer winding workshop shown in About Us.
Large Three Phase Oil Immersed Power Transformer
CNHK large three phase oil immersed transformer for project supply. The published range is above 2000kVA and up to 31500kVA, with voltage up to 38.5kV. Review the conservator, winding, cooling and tap-changer arrangement against the electrical specification.
- Published capacity
- Above 2000 kVA / Up to 31500 kVA
- Published voltage
- Up to 38.5 kV
- Construction
- Conservator type
Select the configuration against your project specification and model-specific data.
PRODUCT OVERVIEW
Large Oil Immersed Transformer for Project Supply
This large three phase oil immersed transformer is described for power-network connections between different voltage levels. Its construction uses an oil conservator, with off-load or on-load tap-changing options. Winding material, terminals, tank and accessories are selected around the project specification and approved drawings.
- Published capacity
- Above 2000 kVA / Up to 31500 kVA
- Published voltage
- Up to 38.5 kV
- Construction
- Conservator type
- Tap-changing options
- Off-load / On-load
The source provides construction details and a broad rating range but no numerical performance table. Losses, impedance, dimensions, mass and the final voltage ratio require selected-design documents. Options described in the text are not universal inclusions.
Product Overview
Large Three Phase Oil immersed power transformers arecustom-built pieces of equipment that are crucial links tothe bulk transmission grid. Usually, they link a generator-transmission line and/or linking lines of different voltages.
CNHK’s Large Three Phase Oil immersed power transformer aremanufactured and tested in accordance the IEC60076
Type Designation
Construction features
The transformers are of the breathing, conventional type provided with an oil conservator.
Two types of transformers are manufactured:
Transformers with off-load tap changer
Transformers with on-load tap changer
Core
The three legged bolt-less core is constructed of grain oriented steel laminations. The joints between the leg and yokeare mitred at 45° and interleaved. The cross section of the leg is circular.
Windings
The material of the windings is either copper or aluminum. The windings are made of paper insulated rectangular wire inthe form of multilayer, disc or helical windings. Transformers provided with on-load tap-changer usually have a separate tap winding.
Off-load tap-changer
The transformers are normally equipped with a 5-position off load tap-changer on the High Voltage side, with its handle located on the cover. When changing the tap position the transformer has to be un-energized. Position 1 of the tap-changer (+ position) corresponds with the highest ratio, which gives the lowest voltage on the Low Voltage side. Position5 of the tap-changer (- position) corresponds with the lowest ratio which consequently gives the highest voltage on the Low Voltage side.
On-load tap-changer
The on-load tap-changer is mounted on the cover of the main transformer tank. The tap changer works as a selectorswitch combining the features of a diverter switch and a tap selector. The selector switch is located in a separate oilcompartment which is connected to its own conservator. The selector switch is of the high-speed spring operated typewith resistive transition impedances. The tap-changer is equipped with a protective relay. The selector switch can belifted for inspection and the oil in the compartment can be changed separately. The on-load tap -changer is providedwith a motor drive mechanism for remote and local control. Normally the motor drive is three-phase and the controland the heating circuits are for single phase AC supply. When re-quested, DC circuits can be supplied.
Insulating oil
The mineral oil used in the transformers complies with IEC 296 and several national standards. The oil slows down the ageing process.
Tank
The transformer tank is usually of the rigid type provided with removable radiators connected to the tank by means of ashut-off valve. On request, the tank can be made vacuum proof.
Transformers up to 5 MVA can be supplied with a compact tank with corrugated cooling fins.
Painting and surface treatment Prior to the painting of the tank, the cover and oil conservator are sandblasted. External surfaces are painted immediately after pre-treatment with a two-pack epoxy primer coat.
Corrugated tanks are flow painted with alkyd primer and acryic finish to a total thickness of 80 um. The conservator and the bottom part of the tank are painted internally.
Options and accessories
The transformers are fitted with the following
standard accessories:
-Bushings
– Oil conservator with oil level indicator
-Filling and drain valves
-Oil sampling device
-Earthing terminals
– Lifting lugs
-Jacking pads (radiator tanks)
-Rating plate
-Silica-gel breather
-Buchholz relay
-Top oil thermometer
Additional accessories can be fitted in accordance with the customer’s specifications.
Vacuum treatment
Drying and vacuum treatment takes place in a special oven, where the windings are heated electrically while simultaneously the air is evacuated from the oven, reaching an absolute pressure of 1 mbar. The transformer is filled with oil while it is still under vacuum. In this way moisture and gases are effectively remo ved from the windings and oil.
Bushings
The bushings are of a solid porcelain type and located on the cover. Bushing insulators canbushings comply with IEC 137. be changed without opening the transformer. The
The terminals can be provided with an air insulatedenclosure. The enclosure can be on the primary and/or onthe secondary side and may be constructed for cable orbus duct connection. Alternatively the transformers can be provided with plug-in bushings.
SELECTION GUIDE
Specify Large Three Phase for Your Project
Electrical duty and rating
Send the required capacity, primary and secondary voltage, frequency, vector group and impedance. Include the network connection and duty so a project-specific data sheet can be prepared.
Tap-changing arrangement
Specify whether the project needs off-load or on-load tap changing. For an on-load arrangement, include the control supply, local or remote operation and monitoring requirements for technical review.
Tank, cooling and connections
Provide the installation layout, required tank arrangement and cable or bus-duct interface. The source describes radiator tanks, corrugated tank options and alternative terminals; agree the selected construction in the outline drawing.
Accessories and acceptance
Identify protection and monitoring signals, inspection requirements and applicable project standards. Request the agreed losses, dimensions, mass, test records and packing information before technical approval.
MANUFACTURING AND PROJECT EXPERIENCE
Project Support from Huanghua Group
Huanghua Group manufactures power transmission and distribution equipment under the CNHK brand. Its published company resources include transformer winding, coil processing and a transformer drying oven. Project support covers selection, drawings, documentation, inspection arrangements and after-sales coordination.
Coil Processing
Company coil processing equipment shown in About Us.
Transformer Drying Oven
Company transformer drying oven shown in About Us.
Power Distribution Project Experience
Company resources and project references do not establish a test certificate for the selected equipment model.
Huanghua Group’s Greece PV Substation Project describes substation and distribution equipment, coordinated protection and site documentation. Review it as a company project reference; the published case does not identify the selected equipment model.
PROJECT SUPPORT
Service and Technical Documents
Technical Service and Documentation
Share the electrical requirements, selected configuration and destination standard. Huanghua Group coordinates technical questions, drawings, document requirements, inspection arrangements and after-sales follow-up against the confirmed product and order scope.
OEM and Project Integration
CNHK’s published OEM and ODM programme covers distribution transformers and power distribution equipment. Discuss equipment configuration, integration, labels, packing and project documents. Confirm the equipment-specific OEM scope, branding and customization requests before they become part of the order.
Documents to Confirm with Your Enquiry
- Selected-model data sheet and outline drawing
- Electrical interfaces and connection requirements
- Agreed inspection records and available certificates
- Manuals, packing list and shipment documents
The document package follows the selected configuration, destination requirements and confirmed order.
Compare Oil-Immersed Transformer Designs
Review the oil-immersed range, then request the selected design’s electrical data and installation drawing.
Related Products
TECHNICAL FAQ
Large Three Phase Questions and Answers
Large or Medium Oil-Immersed Transformer?
The large range describes conservator construction and off-load or on-load tap-changing options. The separately published medium range includes different tank and rating information. Compare the actual project rating and installation requirements rather than treating these pages as one specification.
Oil-immersed transformer rangeWhat rating range is published for this large transformer?
The original summary states above 2000kVA and up to 31500kVA, with voltage up to 38.5kV. These are range limits, not a complete selected-design rating. Provide the actual electrical duty for the quotation.
Does this page publish loss and dimension tables?
No. It describes construction, windings, tap changers, tank and accessories without a numerical performance table. Request losses, impedance, dimensions and mass for the selected design; another product’s table is not a substitute.
Are both tap-changing arrangements available?
The source describes transformers with off-load tap changers and transformers with on-load tap changers. The selected arrangement, tap range, control supply and accessory scope need to be stated in the technical agreement.
Can winding material and terminals be specified?
The original text describes copper or aluminium windings and several terminal or enclosure options. Send the required winding material, cable or bus-duct interface and drawings so the applicable arrangement can be reviewed.
What should be sent for a large transformer quotation?
Provide capacity, voltage ratio, frequency, vector group, impedance, tap-changing requirements, cooling and site conditions. Add layout, monitoring signals, quantity, destination and the required document and inspection package.
Request a Large Three Phase Quote
Send your electrical configuration, drawings, quantity and destination. Our team will review the requirements and the information needed for a quotation.
Request a Quote
PROJECT ENQUIRY
Send Inquiry
Send your Large Three Phase configuration, quantity and destination.
Huanghua Group will review your requirements for a quotation.
Your Project Requirements
- Rating and construction
- Capacity, voltage ratio, frequency, vector group, impedance, tap changer, tank and terminal requirements.
- Quantity and destination
- Order quantity, destination market and requested delivery date for review.
- Drawings and documents
- Site drawings, electrical interfaces and the required document or inspection list.