I. Project Overview and Technical Specifications of the 110/20/10kV Three-Winding Oil-Immersed Power Transformer Project in Romania

This customized solution is developed by Hengfengshuai Electric for a power grid renovation and power supply project in Romania, delivering a full-process packaged solution for two three-phase three-winding oil-immersed power transformers, including one 25MVA unit and one 16MVA unit. The enterprise has years of experience in exporting power transmission and transformation equipment to Eastern Europe. All products strictly comply with IEC 60076, GB 1094 and Romanian SR EN power standards, and are suitable for outdoor operation under local working conditions: altitude ≤1200m, four distinct seasons with temperatures ranging from -30°C to +42°C, winter frost, rainy and highly humid summers, coastal salt fog corrosion and large diurnal temperature variations. The equipment is compatible with Romania’s 50Hz standard power grid, supports three-level voltage networking of 110kV main grid, 20kV regional grid and 10kV distribution grid, and guarantees stable power supply for residents, industrial and mining loads, as well as grid connection of distributed photovoltaics.
The transformers adopt the standard connection group Yn/Yn/D-0-11 with copper windings, featuring low no-load loss and ultra-high energy efficiency PEI. Fixed short-circuit impedance matches the setting values of short-circuit protection of Romania’s power grid. Equipped with dual cooling structures of outdoor oil natural air cooling / oil forced air cooling, the equipment can resist frost, withstand high humidity and prevent salt fog corrosion, balancing stable voltage regulation and long-term low-energy-consumption operation of the power grid.

Master Table of Full Technical Parameters of Transformers

Parameter Name	25MVA (110/20/10kV) Model	16MVA (110/20/10kV) Model	Remarks
Equipment Type	Three-phase three-winding oil-immersed power transformer	Three-phase three-winding oil-immersed power transformer	Special transformer for three-level voltage connection and power transformation of 110/20/10kV
Rated Capacity	HV / MV / LV: 25000kVA	HV / MV / LV: 16000kVA	For graded load power supply of substations
Rated Frequency	50Hz	50Hz	Standard frequency of Romania’s power grid
Maximum Operating Voltage	HV: 126kV; MV: 24kV; LV: 12kV	HV: 126kV; MV: 24kV; LV: 12kV	Meet overvoltage operation requirements for 20kV voltage class
Rated Line Voltage	HV: 110kV; MV: 20kV; LV: 10kV	HV: 110kV; MV: 20kV; LV: 10kV	Strictly match model specification 110/20/10kV and standard voltage classes of Romania
Winding Connection Group	Yn/Yn/D-0-11	Yn/Yn/D-0-11	Neutral points of high and medium voltage star windings are connectable to ground; low voltage delta winding suppresses triple harmonics
Energy Efficiency Index (PEI)	≥99.7%	≥99.663%	Exceed national energy-saving standards, in line with Romania’s power grid low-carbon consumption reduction policies
Short-Circuit Impedance	HV-MV: 10.5%; MV-LV: 6.5%	HV-MV: 10.5%; MV-LV: 6.5%	Unified impedance facilitates unified setting and calibration of relay protection values for Romania’s power grid
No-Load Current	≤0.7%	≤0.66%	Ultra-low no-load loss, higher energy efficiency under light load conditions
Winding Material	High-purity electrolytic copper wire	High-purity electrolytic copper wire	Excellent electrical conductivity, strong resistance to short-circuit impact and aging under wide temperature fluctuations
Cooling Mode	ONAN (Oil Natural Air Natural) / ONAF (Oil Natural Air Forced)	ONAN / ONAF	Natural cooling in low-temperature winter; fans automatically activated for heat dissipation in high-temperature summer
Operating Environment	Altitude ≤1200m, ambient temperature -30°C ~ +42°C, winter frost, rainy & humid summers, coastal salt fog, large diurnal temperature difference	Altitude ≤1200m, ambient temperature -30°C ~ +42°C, winter frost, rainy & humid summers, coastal salt fog, large diurnal temperature difference	Specially optimized for dual working conditions of inland plains and coastal salt fog in Romania (unified conflicting altitude parameters mentioned earlier)
Applicable Standards	IEC 60076, GB 1094, Romanian SR EN power standards	IEC 60076, Romanian SR EN power standards	Meet access certification requirements of Romania’s national power grid ANRE

II. Reasons for Adopting the Customized 110/20/10kV Three-Winding Power Transformer Solution for Romania

Tailored to the three-level voltage networking demand of Romania’s power grid, Hengfengshuai Electric provides a matched set of 25MVA and 16MVA three-winding transformers. The solution features five core strengths: three-level integrated power supply, ultra-high energy efficiency, frost and salt fog resistance, easy operation & maintenance, and full compliance with Romania’s SR EN power grid specifications, perfectly suiting the needs of urban and rural substations, industrial & mining parks and photovoltaic booster stations in Romania.

1. Integrated three-winding design cuts civil engineering and equipment investment by realizing three-level grid connection with one unit

Conventional schemes require separate configuration of two double-winding transformers (110/20kV and 20/10kV). Our single unit integrates high-voltage 110kV, medium-voltage 20kV and low-voltage 10kV windings, completing electric energy conversion for three voltage levels via one single device.

• Substation floor space is reduced by over 35%, with significant cuts in investment on civil foundations, cables and supporting switchgears;

• The combination of 25MVA and 16MVA units enables flexible power supply schemes such as one unit for operation and one for standby, or zoned power supply for loads of varying magnitudes, supporting flexible load regulation and matching the expansion & renovation projects of new urban districts in Romania.

2. Ultra-high PEI energy efficiency index drastically reduces full-lifecycle loss costs

The PEI indicators of both models surpass conventional national and IEC standards, with no-load current controlled below 0.7%:

• Copper windings paired with high-permeability silicon steel sheets deliver low no-load loss and load loss, maintaining high efficiency under both light and full load conditions;

• Romania’s power grid runs non-stop all year round. Each transformer can save tens of thousands of kWh of power loss annually, bringing remarkable long-term savings on electricity bills and complying with ANRE energy efficiency control and clean energy development policies of the country.

3. Unified standard short-circuit impedance compatible with Romania’s national power grid relay protection system

Unified short-circuit impedance parameters (10.5% for HV-MV and 6.5% for MV-LV) fully conform to Romania’s ANRE power grid design specifications:

• Controllable short-circuit current prevents winding damage caused by system short-circuit faults;

• Owners are exempt from recalculating protection setting values, greatly improving the efficiency of calibration and commissioning for differential protection, backup protection and ground protection of substations, lowering technical difficulties for local Romanian power technicians during on-site commissioning.

4. Special weather-resistant design against salt fog and frost for inland frigid and coastal humid working conditions in Romania

Special upgrades are made to cope with Romania’s winter frost, rainy & humid summers, Black Sea coastal salt fog corrosion and extreme diurnal temperature fluctuations:

• Low-pour-point special insulating oil and weather-resistant EPDM sealing components retain stable fluidity and sealing performance at -30°C without leakage or insulation failure;

• Multi-layer composite coating of epoxy zinc-rich primer and salt-fog-resistant topcoat on the outer tank wall resists sea salt fog, ultraviolet radiation and freeze-thaw cycles, allowing long-term open-air installation for both inland and coastal substations;

• Dual-mode cooling system automatically shuts down fans in cold winter to cut energy consumption and activates forced air cooling in hot & humid summers, keeping oil temperature stable all year round.

5. Standard Yn/Yn/D-0-11 connection suppresses harmonics and improves power quality of distribution grids

The delta winding on the low-voltage side effectively counteracts triple harmonics in the system, addressing harmonic pollution induced by non-linear loads such as industrial & mining equipment and distributed photovoltaics in Romania:

• Reduces harmonic voltage distortion on the 10kV side to protect downstream motors, photovoltaic inverters and residential electrical appliances;

• Flexible grounding of high and medium voltage neutral points adapts to mainstream neutral grounding grid architectures of Romania’s 110kV and 20kV power grids, enhancing operational stability during grid faults.

6. Copper windings with strong short-circuit resistance lower maintenance failure frequency

All electrolytic copper windings feature optimized conductor cross-section and rigid reinforcement of winding ends, passing all short-circuit withstand type tests per SR EN standards:

• Windings are less prone to deformation and insulation damage under sudden short-circuits, drastically cutting on-site maintenance and replacement costs;

• Ultra-low no-load current eliminates hidden heat risks during long-term light-load operation, suitable for unattended substations in remote Romanian towns and villages.

III. Design & Development Phase of the 110/20/10kV Power Transformer for Romania

Customized Electromagnetic Simulation Design

Combining Romania’s power grid parameters, salt-frost climate and SR EN standards, the technical team of Hengfengshuai Electric conducts electromagnetic simulation calculations:

1. Correct winding temperature rise and insulation withstand parameters based on -30°C low temperature and high-humidity summer environments, and optimize vertical & horizontal oil duct structures to balance oil fluidity at low temperatures and heat dissipation under high temperature & humidity;

2. Adopt ultra-low-loss high-permeability grain-oriented silicon steel sheets, precisely calculate no-load current and loss to guarantee compliance with high PEI energy efficiency indicators and meet ANRE access requirements for energy-saving equipment;

3. Strictly match standard short-circuit impedance of 10.5%/6.5%, optimize winding layout by layers to control magnetic leakage and suppress harmonic output at the source;

4. Increase insulation creepage distance for coastal high-humidity and salt fog ionization environments, strengthen suppression of partial discharge under humid conditions and meet mandatory insulation standards for outdoor high-voltage equipment in Romania.

Specialized Optimization of Complete Structural Drawings

After finalizing the electromagnetic scheme, 3D structural drawings are designed with targeted improvements for Eastern European working conditions in Romania:

• The iron core adopts multi-stage step-lap stacking technology with composite shock-absorbing clamps, avoiding loosening under frost temperature fluctuations and long-distance transportation vibration, and operating noise stays below substation limit values specified locally;

• Multi-layer composite insulation structure for three windings, with refined multi-layer wrapping of high/medium voltage angle rings and electrostatic plates to improve moisture-proof insulation performance under high humidity and salt fog;

• The oil tank is fabricated with thickened low-alloy weather-resistant steel plates and double-layer epoxy zinc-rich anti-salt-fog anti-corrosion coating; flanges and cover plates adopt double sealing structures to block rainwater and sea fog penetration;

• Cooling radiators, conservators, bushings, temperature control systems and all auxiliary parts are special accessories resistant to -30°C low temperature and salt fog, matched with low-pour-point and moisture-resistant transformer oil.

Joint Scheme Review by Multiple Departments

Upon completion of drawings and electromagnetic schemes, a joint review is organized by the electromagnetic design, process, quality inspection and overseas Eastern Europe project teams to verify item by item: power grid voltage matching, insulation & heat dissipation under salt fog and frost, anti-corrosion structures, cross-border transportation dimensions for China-Europe Railway Express, Romanian SR EN certification & ANRE grid access standards, and on-site local installation convenience. Production commences only after full review approval.

IV. Manufacturing Phase of the 110/20/10kV Power Transformer for Romania

1. Full Inspection of Raw Materials upon Warehousing (ISO9001 Full-Process Control)

All core raw materials are purchased to customized standards for the Romanian project and undergo 100% full-item testing upon arrival; unqualified materials are isolated and prohibited from use:

• High-permeability silicon steel sheets: test loss and magnetic permeability to strictly control no-load current indicators and meet PEI energy efficiency requirements;

• Electrolytic copper wires: test resistivity and low-temperature bending strength to guarantee stable mechanical performance under frost conditions;

• Insulating materials: insulating boards, end rings and angle rings are tested for water content and electrical strength under humid conditions to eliminate risks of insulation breakdown in high-humidity salt fog environments;

• Weather-resistant transformer oil: test pour point, breakdown voltage, oxidation resistance and hydrolysis resistance to adapt to wide temperature & humidity variations throughout the year in Romania;

• Sealing parts and tank steel plates: special accelerated aging tests for low-temperature resistance, freeze-thaw resistance and salt-fog aging resistance. Qualified materials are stored in constant temperature & humidity warehouses with independent zones under strict dust-proof, moisture-proof and metal dust control.

2. Precision Machining of Iron Cores

Fully automatic longitudinal and transverse shearing equipment cuts silicon steel sheets, removes burrs and coats with high-temperature moisture-proof insulating paint; multi-stage step-lap stacking reduces joint magnetic resistance to control no-load loss and operating noise; precise clamping force is applied after stacking, with rubber shock-absorbing buffer components installed to prevent loosening caused by transportation and temperature vibration. After iron core fabrication, no-load loss and no-load current are measured on-site and calibrated against design values before flow to the next process.

3. Winding of Three Windings in Dust-Free Workshop

High-voltage windings, 20kV medium-voltage windings and 10kV low-voltage delta windings are all manufactured in a Class 10,000 clean constant temperature & humidity workshop: winding turns, wire transposition and coil compactness are strictly controlled to match electrical characteristics of the Yn/Yn/D-0-11 connection group; widened low-temperature oil ducts are reserved inside to guarantee oil circulation and heat dissipation under low temperatures. Each coil undergoes testing of DC resistance, winding turns and appearance upon completion to rule out wire damage and turn deviation. Revision Note: Remove the incorrect text "35kV medium voltage winding" in the original document.

4. Salt-Fog Resistant Processing & Deep Drying of Insulating Components

CNC equipment precisely cuts insulating components; multi-layer manual fine wrapping is applied to high/medium voltage end insulation and angle rings to extend creepage paths and suppress partial discharge triggered by moisture and salt fog. All insulating components are sent to high-temperature vacuum drying tanks for deep dehydration to eliminate free internal moisture and prevent insulation aging caused by rainy summers and coastal high humidity in Romania.

5. Forming & Anti-Salt-Fog Anti-Corrosion Processing of Oil Tanks

Steel plates are blanked by CNC cutting and fully sealed via automatic submerged arc welding; each tank undergoes kerosene leakage inspection and long-duration air tightness test to eliminate hidden welding seam leakage risks. After welding, sand blasting and passivation are performed, followed by layered spraying of multi-layer epoxy zinc-rich primer and salt-fog-resistant topcoat; double sealing structures are optimized for tank flanges and cover plates. Finished oil tanks pass positive and negative pressure mechanical strength tests to resist tank deformation and leakage during long-distance transportation and alternating freeze-thaw cycles.

6. Standard Assembly of Active Part

Qualified iron cores and three groups of coils are precisely fitted, followed by sequential installation of customized insulating components, high/medium/low voltage leads, tap changers and temperature control sensors. The whole assembly process is dust-controlled to avoid insulation faults induced by residual metal dust. High-temperature silver brazing of leads improves mechanical strength under low temperature and high humidity. Three-side wiring terminals are reserved strictly in accordance with Romania’s 110/20/10kV power grid standards to match local cable laying specifications. Full inspection of structure, wiring and insulation gaps is completed after assembly.

7. Three-Stage Vacuum Deep Drying (Adapted to High Humidity & Frost Climate in Romania)

To address easy moisture absorption caused by Romania’s winter frost, rainy summers and coastal high humidity, a three-stage vacuum drying process is implemented: a. Pre-drying of single coils: remove moisture adsorbed during winding; b. Intermediate drying after core-coil fitting: eliminate moisture introduced during assembly; c. Ultimate high-temperature vacuum drying of the entire active part: thoroughly remove deep water vapor inside insulation to guarantee stable insulation resistance under high humidity and low temperature conditions.

8. Final Assembly & Weather-Resistant Vacuum Oil Filling

Qualified dried active parts are lifted into oil tanks, followed by sequential installation of bushings, conservators, plate radiators, cooling fans, gas relays, temperature control protection instruments and other accessories. Secondary application of low-temperature sealant reinforces all pipelines and flanges. After long-duration high-vacuum pressure maintenance of the complete unit, special low-temperature salt-fog-resistant insulating oil is slowly injected at low speed to fully exhaust bubbles, ensuring long-term stable insulation performance under high humidity and frost conditions.

V. Factory Acceptance Test (FAT) Verification of the Romania 110/20/10kV Power Transformer

Prior to delivery, both transformers complete a full set of routine tests in strict accordance with IEC 60076, GB 1094, Romanian SR EN power standards and ANRE grid access testing requirements. The first prototype additionally undergoes a full set of type tests. Delivery is permitted only after all indicators meet standards and bilingual factory test reports (Romanian + Chinese & English) are issued.

1. Mandatory Routine Tests for Each Unit

• DC resistance testing of windings across all tap positions, with three-phase unbalance rate controlled within SR EN standard limits;

• Verification of transformation ratio and connection group across all tap positions to confirm accurate Yn/Yn/D-0-11 phase sequence;

• Testing of insulation resistance, absorption ratio and polarization index to simulate insulation performance under high humidity and low temperature in Romania;

• Detection of dielectric loss factor, with insulation system indicators superior to IEC and local Romanian standards;

• Power frequency withstand voltage test of windings together with bushings, with no breakdown or flashover throughout the test;

• Full inspection of insulating oil: breakdown voltage, micro-water content, chromatography, low-temperature fluidity and salt-fog hydrolysis resistance;

• Measurement of no-load loss and no-load current to meet PEI energy efficiency design values and ANRE energy-saving indicators;

• Short-circuit impedance test at rated tap to strictly guarantee HV-MV=10.5% and MV-LV=6.5%;

• Linked test of dual cooling systems to verify automatic fan start/stop under high and low temperature conditions;

• Temperature & humidity composite simulated temperature rise test to confirm stable heat dissipation across the full temperature range of -30°C ~ +42°C.

2. Full Set of Type Tests for the First Prototype

Rigorous type tests are carried out on the 25MVA prototype to verify adaptability to composite extreme working conditions of inland and coastal areas in Romania:

• Lightning impulse insulation test to verify tolerance against lightning overvoltage under outdoor thunderstorm weather;

• High-voltage high-humidity partial discharge test to eliminate hidden partial discharge risks in coastal salt fog and humid environments;

• Dynamic and thermal stability tests under sudden short-circuit to verify short-circuit deformation resistance of copper windings;

• Accelerated salt-fog aging simulation test: 720 consecutive hours of salt fog spraying with no corrosion and no attenuation of insulation performance;

• High-low temperature cycle durability test: 72 consecutive hours of cyclic operation from -30°C frost to +42°C high temperature with no abnormalities.

VI. Cross-Border Packaging & Transportation Phase of the Romania 110/20/10kV Transformer

Split Protective Packaging Design

After passing all tests, precision accessories including bushings, radiators, temperature control instruments and protection devices are individually sealed in shockproof, moisture-proof and rust-proof wooden boxes. Sealing cover plates are installed on all body interfaces of the transformer, and the tank is filled with dry nitrogen for moisture and salt fog prevention. The complete unit is mounted on a heavy-duty steel transport frame and wrapped with thickened waterproof, frost-proof and salt-fog-proof tarpaulins on the exterior. International large-piece warning signs for China-Europe Railway Express and sea freight are marked on the tank. Attached with the unit are Romanian-English bilingual operation manuals, full test reports, SR EN certification documents and spare parts lists.

Cross-Border Logistics Scheme via China-Europe Intermodal Transport

An intermodal transport model of "domestic highway + China-Europe Railway Express rail transport + local Romanian transshipment" is adopted for large-piece inland transportation in Eastern Europe. Customs clearance documents and large-piece road transport permits for both countries are processed in advance. Temperature, humidity and 3D impact recorders are installed throughout transportation to monitor real-time data of low temperature, vibration and humidity. Reinforced protection against frost, collision and salt fog is added during rail transport to avoid risks of low-temperature frost damage and vibration deformation during long-distance transit, with direct delivery to the substation site in Romania.

VII. On-Site Delivery, Installation & Commissioning of the Romania 110/20/10kV Transformer

1. Joint Unboxing Acceptance on Site

Upon arrival of equipment at the Romanian substation, the overseas technical team of Hengfengshuai Electric conducts joint unboxing acceptance together with the owner, local Romanian power supervisors and power grid operation & maintenance units: check the body and accessories for rust, collision damage and leakage; verify accessory model and quantity fully match the packing list; test nitrogen sealing pressure of the tank for no leakage; retrieve full transportation recorder data to confirm no abnormal conditions during transit. Official handover documents are signed only after all inspection items pass, complying with ANRE on-site acceptance procedures.

2. Standardized On-Site Installation Adapted to Salt Fog & Frost Environments

Overseas resident engineers provide full-process installation guidance suitable for open-air working conditions of rainy, frosty and coastal salt fog environments in Romania: a. Precise positioning via professional hoisting equipment, with equipment levelness strictly calibrated to errors complying with SR EN installation specifications; b. Sequential installation of radiators, cooling fans, three-side bushings, conservators, temperature control, gas protection and other accessories; low-temperature salt-fog-resistant sealant is reapplied on all flanges for multi-layer reinforcement against leakage; c. Secondary vacuum pumping of the complete unit, replenishment of identical weather-resistant insulating oil, and full-cycle filtration to remove impurities and water vapor in oil; d. Long-duration static standing for layered gas separation, with repeated venting of residual gas in pipelines and relays to eliminate hidden gas gap discharge faults under high humidity.

3. Full Set of On-Site Acceptance Test (SAT) for Handover

After installation and static standing, a full set of on-site tests is carried out in accordance with Romanian SR EN and ANRE power grid operation & maintenance specifications, with item-by-item comparison against factory FAT reports: insulating oil testing, winding DC resistance, transformation ratio & connection group, insulation resistance, winding deformation, cooling system linkage, full relay protection circuit calibration, partial discharge re-test and power frequency withstand voltage re-test. Official locally recognized test records are issued only after all test data qualify and protection devices act sensitively and reliably.

4. No-Load Impact Switching and On-Load Commissioning

After all handover tests pass, the operation site is cleaned and safety protection & electrical wiring restored. Multiple no-load impact closing operations are performed in compliance with Romania’s national power grid commissioning specifications to monitor excitation inrush current, equipment sound and oil temperature variations. Continuous stable no-load operation is maintained for 24 hours with full monitoring of temperature rise, vibration and leakage under frost and high-temperature conditions with no abnormalities. Load is gradually applied in stages before the transformer is officially put into commercial operation connected to Romania’s 110/20/10kV three-level power grid.

VIII. Full-Process Quality Control & Localized Operation & Maintenance Support

Six Core Quality Control Points (Adapted to Romanian Eastern Europe Export Projects)

a. Design Control: Multi-review of salt-fog anti-corrosion, low-temperature insulation, three-winding impedance and energy efficiency indicators to comply with Romanian SR EN and ANRE power grid standards; b. Material Control: 100% incoming inspection of all raw materials, with independent quality control channels for special low-temperature and salt-fog-resistant accessories; c. Process Control: Item-by-item inspection of iron core, coil, insulation and assembly processes, with image retention of key processes for full traceability of quality; d. Test Control: Two-way comparison of factory FAT and on-site SAT test data; unqualified equipment is prohibited from factory delivery and grid commissioning; e. Transportation Control: Frost and salt-fog resistant reinforcement for China-Europe Railway Express transit, with real-time monitoring via recorders to avoid equipment damage during long-distance cross-border transportation; f. On-Site Control: Full-process supervision of on-site installation, testing and commissioning by overseas engineers in strict compliance with local Romanian substation construction standards.

Romanian-English Bilingual Technical Documents & Local Operation & Maintenance Training

After project commissioning, a full set of bilingual technical archives (Romanian & English) is delivered to the client: complete structural drawings, factory test reports, special operation & maintenance manuals for salt fog and frost environments, spare parts lists, SR EN certification documents and ANRE grid access filing records. Special practical training is provided for local Romanian operation & maintenance personnel, focusing on regular inspection for coastal salt-fog anti-corrosion, winter frost protection maintenance, fault troubleshooting under high humidity and all-season operation & maintenance key points of dual cooling systems, lowering later operation & maintenance costs and technical barriers for owners.

IX. Scheme Summary

This complete packaged solution for 2 units (25MVA + 16MVA) of 110/20/10kV three-winding oil-immersed power transformers for Romania serves as a benchmark export project of Hengfengshuai Electric customized for the temperate continental climate, 110/20/10kV three-level voltage power grid and Black Sea coastal salt fog working conditions of Romania. Equipped with customized anti-salt-fog & anti-frost insulation and anti-corrosion design, ultra-high energy efficiency copper windings, unified SR EN standard short-circuit impedance and integrated three-winding structure, the product fully addresses core local demands including multi-level voltage connection of substations, stable operation under extreme annual temperature & humidity fluctuations, coastal salt fog corrosion, power grid harmonic control and long-term energy consumption reduction.
Hengfengshuai Electric has deep experience in exporting power equipment to Eastern European power markets and is fully familiar with Romanian SR EN standards, ANRE grid access certification, IEC and GB standards. We can customize integrated solutions for 10kV~220kV full-capacity oil-immersed three-winding and double-winding power transformers according to power grid voltage, climate and load demands of various Eastern European countries, supporting Romania’s power grid upgrading, stable urban and rural power supply, supporting photovoltaic new energy and industrial & mining energy construction. General contractors, power owners and foreign trade clients are welcome for consultation and cooperation. Contact Email: hfs@hengfengshuai.com