• Product advantages
• Product parameters
• Ordering instructions

Product advantages

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Key Advantages of our 35kV Three-Phase Oil-Immersed Power Distribution Transformer

• Leading-Edge Winding Technology: Engineered with advanced high-voltage copper tape winding and low-voltage copper foil winding, this 35kV three-phase oil-immersed power distribution transformer delivers unmatched lightning impulse resistance and features premium Class-A insulation materials.

• Superior Mechanical Strength: Designed with low magnetic leakage and exceptional short-circuit withstand capability, our 35kV three-phase oil-immersed power distribution transformer ensures ultimate grid stability.

• Advanced Step-Lap Core Structure: Utilizing a 45° full-oblique joint step-laminated core structure, this 35kV three-phase oil-immersed power distribution transformer significantly lowers operational noise and no-load losses.

Precision-Engineered Tank & Enclosure

• State-of-the-Art CNC Fabrication: The tank of the 35kV three-phase oil-immersed power distribution transformer is processed using top-tier Mitsubishi laser cutting machines and advanced CNC punching and bending equipment to guarantee flawless dimensional accuracy.

• Robot Automatic Welding & Zero-Leakage: Featuring ABB robotic automatic welding and high-precision laser detection, the enclosure eliminates any risk of oil leakage, boasting an extraordinary quality qualification rate of 99.99998%.

• 50-Year Ultra-Durable Coating: Treated with premium electrostatic powder spraying, the anti-corrosion coating system offers exceptional hardness ($\ge 0.4$) and salt spray resistance within 100h, promising up to 50 years of paint durability.

• Fully Sealed & Maintenance-Free: The fully sealed structure protects the cooling medium from aging, offering a maintenance-free service life exceeding 30 years for the 35kV three-phase oil-immersed power distribution transformer.

High-Efficiency Iron Core & Coils

• Premium Silicon Steel Core: The iron core of our 35kV three-phase oil-immersed power distribution transformer is built from high-quality, cold-rolled grain-oriented (CRGO) silicon steel sheets with mineral oxide insulation (sourced from industry giants like Baosteel and Wisco). By controlling precision cutting and stacking, we minimize no-load current and acoustic noise.

• Patented Winding Innovation: While the low-voltage coils utilize high-grade copper foil for excellent insulation resistance, the high-voltage windings leverage Hengfengyou Electric’s patented technology using insulated copper wire, providing supreme resistance to radial stresses caused by short circuits.

• Structural Reinforcement: The entire core and coil assembly is specially reinforced to withstand rigorous vibrations during transportation and normal grid operations.

Top-Tier Raw Materials & Components

To ensure the premium quality of each 35kV three-phase oil-immersed power distribution transformer, we only source from world-class suppliers:

• Core Sheets: Baosteel & Wisco high-permeability CRGO silicon steel.

• Conductors: Premium-grade Chinese anaerobic (oxygen-free) copper.

• Insulating Oil: CNPC (PetroChina Kunlun Petroleum) High-Quality 25# Transformer Oil.

Technical Configurations & Safety Standard

• Tinned Copper Connections: Equipped with high-conductivity tinned copper bars for low-voltage outgoing terminals, and robust ring tinned bolts for high-voltage outlet terminals.

• Flexible Tap Changer Options: Standard configuration features a 5-step or 7-step Off-Circuit Tap Changer (NLTC), with On-Load Tap Changer (OLTC) available for customization.

• Advanced Gas Relay Protection: For units rated above 630 kVA, high-sensitivity gas relays are installed as standard to ensure real-time safety monitoring for the 35kV three-phase oil-immersed power distribution transformer.

Why Choose Hengfengshuai 35kV Three-Phase Oil-Immersed Power Distribution Transformer?

As the core power hub for modern green grids and low-carbon industrial projects, choosing Hengfengshuai means choosing a higher grid return on investment (ROI) and significantly reduced operational risks.

Thanks to Hengfengyou Electric's proprietary "Ultra-Low Loss Energy-Saving Power Transformer" patented technology, every Hengfengshuai 35kV three-phase oil-immersed power distribution transformer achieves a 5% saving in raw materials. Compared to standard market alternatives, its comprehensive operational losses are reduced by 10% to 20%.

Whether for urban grid upgrades, large industrial parks, renewable energy plants like wind and solar, or long-distance international transport projects, the Hengfengshuai 35kV three-phase oil-immersed power distribution transformer is your ultimate eco-friendly, energy-saving, and cost-effective turnkey high-voltage power solution.

35kV Three-Phase Oil-Immersed Power Distribution Transformer Case

35kV Three-Phase Oil-Immersed Power Distribution Transformer FAQ

1. Standard & Certification

Q1: What international standards do your 35kV transformers comply with? Can they meet local grid connection standards?
A1: Our products are strictly designed and tested per IEC 60076, IEC 60296 and IEC 60085. We also comply with GB, EN, GOST, ANSI/IEEE, AS/NZS, INMETRO, SABS, KEBS, SASO and other regional grid standards. Provide project country and grid specifications, and we will deliver compliance assessment and certification documents.
Q2: Can you provide full type test reports and third-party witnessed tests? Is WTT available?
A2: Full set of CNAS, KEMA and UL accredited type test reports are available, covering temperature rise, loss, impedance, lightning impulse, switching impulse and sudden short-circuit tests. Factory Witnessed Test (WTT) can be arranged for high-end grid and key EPC projects in advance.
Q3: Are English technical documents available? Do you support multilingual customization?
A3: Standard delivery covers full English technical documents: nameplate, dimension & wiring drawings, FAT report, O&M manual, spare parts list and certification. French, Spanish, Portuguese, Arabic, Russian and other language versions are customizable.

2. Technical Performance

Q4: Do you use copper or aluminum windings? Can you guarantee the winding material in writing?
A4: Pure copper or aluminum windings are optional per client requirements. Winding material can be clearly stipulated in contracts and technical agreements with test & traceability reports provided. 35kV units adopt premium HV insulation for stable performance and aging resistance.
Q5: Can loss, impedance, insulation and temperature rise parameters be customized? What if parameters exceed standards?
A5: Key electrical parameters (loss, impedance, tapping voltage, insulation, temperature rise) can be fully customized per client datasheets. All units undergo full factory testing. Non-compliant products are forbidden for shipment and will be reworked or replaced free of charge.
Q6: Can the transformer adapt to high altitude, salt spray, high humidity, seismic and other harsh environments?
A6: Customized environmental adaptation is available for harsh conditions: high altitude insulation & heat dissipation optimization, C5M-grade coastal anti-corrosion, high humidity moisture-proof sealing and seismic reinforcement. We provide targeted design per your site temperature, altitude, salt spray and seismic data.
Q7: Is the transformer suitable for PV and wind power grid connection? What is the anti-harmonic performance?
A7: Anti-harmonic customized transformers are specially designed for PV and wind power grid connection. Optimized core and winding structure suppress harmonic heating and voltage distortion, adapting to intermittent new energy loads for booster stations and distributed PV projects.
Q8: What is the standard noise level? Is low-noise customization available?
A8: Standard unit noise ≤58dB (IEC test). Low-noise design (≤50dB) is available for residential and municipal scenarios via optimized core, damping and fan configuration. Noise test reports are provided for environmental compliance.
Q9: Can the transformer withstand lightning impulse and sudden short circuit per grid requirements?
A9: 35kV units adopt standard lightning impulse insulation design to resist lightning and switching overvoltage. Enhanced anti-short-circuit structure is equipped for main grid projects, with full short-circuit test reports provided to meet global grid access standards.
Q10: What is the design and actual service life? Does it follow the 6℃ aging rule?
A10: Designed service life is 20 years, and can reach 25-30 years under proper maintenance. The oil-paper insulation follows the 6℃ aging rule, and sufficient temperature rise margin effectively delays insulation aging for longer service life.
Q11: Are you a professional 35kV transformer manufacturer?
A11: Founded in 1990, we are a professional transformer manufacturer based in Qingdao with 30 years of R&D, production and export experience. We produce full-range 35kV and below transformers with in-house core processes, serving global EPC and grid clients. Factory audit is welcome.

3. Customization, Dimension & Transportation

Q12: Do you support non-standard customization? Can accessories and dimensions be customized?
A12: Full non-standard customization is available, including electrical parameters (tapping, impedance, loss, new energy adaptation), structure size and installation mode. Key accessories can be customized with specified international brands. All customized items can be recorded in technical agreements.
Q13: What are the weight and dimensions? Is it suitable for cross-border hoisting and transportation?
A13: Exact weight and dimension data are provided with formal quotation. For large-capacity units, we pre-evaluate over-limit risks and provide professional hoisting and cross-border transportation solutions to ensure smooth delivery.
Q14: Do you ship with full oil or nitrogen-filled protection?
A14: Small & medium units adopt full-oil sealed transport for fast on-site installation. Large units for long ocean shipping adopt oil-discharged & nitrogen-filled transport with impact recorder, protecting windings and insulation during transit.

4. Production & FAT Acceptance

Q15: What is the production lead time? How to guarantee on-time delivery?
A15: Standard delivery: 15-25 working days; customized/large-capacity units: 25-40 working days. Exact lead time is contractually confirmed. We update production progress in real time and give early delay warning with contractual liability guaranteed.
Q16: Is on-site supervision and FAT witnessing supported?
A16: On-site supervision and FAT witnessing by clients or third parties (SGS, BV, etc.) are fully supported. We coordinate schedules and provide full production & test records to ensure transparent and compliant inspection.
Q17: Are core components traceable? Are core processes outsourced?
A17: All core components are 100% batch traceable with complete certification. Key production processes are fully in-house without outsourcing, ensuring stable and reliable product quality.

5. Quotation, Payment & Customs Clearance

Q18: What is the quotation validity? Will prices be adjusted due to raw material fluctuation?
A18: Standard quotation validity: 15 days (price locked). Validity can be extended up to 180 days upon request. Quotation will be renewed after expiry.
Q19: What payment terms do you accept? Is L/C available?
A19: We support TT and irrevocable sight L/C. Advance ratio and payment terms are flexible per project scale, with all terms specified in formal contracts for trade security.
Q20: Can you provide origin certificates for tariff deduction?
A20: We provide CO, FORM E, FORM A and other customs clearance certificates to help clients enjoy tariff preferences and clear customs smoothly.

6. Packaging, Logistics & Insurance

Q21: What is the export packaging standard? Is it salt-proof and moisture-proof? With IPPC mark?
A21: Export packaging adopts professional anti-rust, moisture-proof and shockproof treatment for ocean shipping. All wooden packages have standard IPPC fumigation marks to meet global port quarantine requirements.
Q22: What shipping methods are available for 35kV transformers?
A22: We offer multiple shipping solutions: sea freight for global delivery, bulk carrier for oversize units, China-Europe railway for European & Central Asian inland areas, and trucking for neighboring cross-border projects.
Q23: What is the claim process for cargo damage during transportation?
A23: All goods are fully insured. Clients shall submit insurance application with on-site evidence within 48 hours after arrival. We provide full document support for claim settlement, with final result subject to insurance policy and third-party assessment.

7. SAT & Commissioning Service

Q24: Can you provide overseas on-site installation, commissioning and SAT service?
A24: We provide global on-site services including installation guidance, commissioning, testing, SAT acceptance and O&M training with separate quotation. Free remote technical support is also available anytime.

8. Warranty & After-sales Service

Q25: What is the warranty period and coverage?
A25: Standard warranty: 1 year, extendable to 2-5 years for grid & EPC projects. Warranty covers manufacturing and original accessory defects, excluding improper operation, overload, external damage and unauthorized modification.
Q26: Can you supply original spare parts long-term after warranty expires?
A26: We provide lifetime original spare parts supply for core wearable components, ensuring long-term stable equipment operation without supply interruption.
Q27: What is your technical response time for equipment faults?
A27: 24/7 online technical support for fault troubleshooting. On-site service is available within 7-15 working days upon negotiation. Emergency response is activated for critical faults to minimize project loss.
Q28: How do you control factory quality for 35kV transformers?
A28: Equipped with complete ISO and SQA quality control system, we implement full-process standardized inspection. All 35kV units are fully tested before delivery. Third-party inspection and factory audit (BV, SGS) are supported to meet high-standard grid and EPC requirements.

Product parameters

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  - Input voltage: 35kV

  - Output voltage: 0.4kV
  - Capacity: 50-5000 kva
  - Frequency: 50HZ/60HZ
  - Voltage regulation mode: NLTC (no Load tap changer)
  - Remark: voltage, capacity, frequency, connection group and loss can be customized according to customer requirements

额定容量Capacity	额定电压及分接范围Rated voltage&Off-load tapping				联结组标号 Vector  GroupSymbol		空载损耗 NO-load loss（W）	负载损耗 Load loss（W）	空载电流 NO-load current	短路阻抗Short  circuit impedance(%)
	高压 H.V(kv)	高压分接范围  High pressure   Tap range（%）		低压 L.V(kv)
50 kva	33kV 35kV 38.5kV	±5% ±2x2.5%		0.4	Dyn11 Yyn0		210	1270/1210	2.0	6.5
100 kva							290	2120/2020	1.8	6.5
125 kva							340	2500/2380	1.7	6.5
160 kva							360	2970/2380	1.6	6.5
200 kva							430	3500/3330	1.5	6.5
250 kva							510	4160/3960	1.4	6.5
315 kva							610	5010/4770	1.4	6.5
400 kva							730	5050/5760	1.3	6.5
500 kva							860	7280/6930	1.2	6.5
630 kva							1040	8280	1.1	6.5
800 kva							1230	9900	1.0	6.5
1000 kva							1440	12150	1.0	6.5
1250 kva							1760	14670	0.9	6.5
1600 kva							2120	17550	0.8	6.5
2000 kva							2490	20740	0.8	6.5
2500 kva							2950	24420	0.8	6.5
3150 kva							3510	29050	0.7	6.5
4000 kva							4200	34940	0.7	6.5
5000 kva							4960	41160	0.7	6.5

Ordering instructions

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 - Main parameters of transformer (voltage, capacity, loss and other main parameters)
- Transformer operating environment (altitude, temperature, humidity, location, etc.)
- Other customization requirements (tap switch, color, oil pillow, etc.)
- The minimum order quantity is 1 sets, worldwide delivery within 7 days
- Normal delivery period of 30 days, worldwide fast delivery