HENGFENGYOU TRANSFORMER|ANSI/IEEE STANDARD TRANSFORMER
HENGFENGYOU TRANSFORMER|ANSI/IEEE STANDARD TRANSFORMER
This Dubai desert photovoltaic park project is equipped with 20 units of 2.5 MVA‑690/11 kV three‑phase oil‑immersed step‑up transformers, custom‑developed for the large‑scale desert PV power plant in Dubai, UAE. It provides an all‑in‑one solution to seven core challenges under the combined desert‑coastal operating conditions in Dubai, UAE: extreme high‑temperature exposure in summer, huge day‑night temperature difference, desert sand and dust covering heat‑dissipation equipment, coastal salt‑fog corrosion, bidirectional power flow of photovoltaic systems, harmonic interference from inverters, and compliance with DEWA grid‑connection specification UAE.S 5010‑1.
Hengfengyou Electric has rich experience in export and delivery of high‑voltage distribution and step‑up transformers for the Middle East and UAE markets. Products strictly comply with the IEC 60076 series standards, satisfy the UAE.S 5010‑1 distributed generation grid‑connection technical requirements of Dubai Electricity and Water Authority (DEWA), and meet local ESMA product access regulations. The low‑voltage side receives electric energy output from photovoltaic inverters and steps up the voltage to 11 kV for medium‑voltage transmission. Serving the large‑scale desert PV power plant in Dubai, it boosts the low‑voltage electric energy converted from photovoltaic DC power for transmission to the 11 kV collection grid within the park and ensures stable power export of the PV station.
a. Extreme high‑temperature solar exposure in desert summer: Ambient temperature ranges from ‑5 ℃ to +45 ℃. Ground surface temperature rises drastically in summer under long‑time intense solar radiation. Ordinary transformers feature insufficient temperature‑rise margin and are prone to over‑temperature alarms and shutdowns. Ultraviolet rays accelerate aging of fuel‑tank paint and sealing rubber parts and greatly shorten insulation service life.
b. Desert sand‑dust clogging heat‑dissipation systems: Frequent desert sandstorms cause sand and dust to adhere to radiator surfaces, block heat‑dissipation passages and reduce heat‑dissipation efficiency. Intrusion of conductive sand‑dust increases risks of insulation flashover and threatens safe equipment operation.
c. Coastal salt‑fog corrosion aggravated by large day‑night temperature difference: Dubai borders the gulf with salt‑laden air. Wide day‑night temperature differences easily trigger condensation inside the tank, resulting in tank corrosion, seal water seepage and deterioration of internal insulation performance.
d. Bidirectional power flow for photovoltaic working conditions: During daytime, the PV station generates power and feeds electricity to the grid; at night with no PV output, transformers operate under bidirectional power flow. Improper selection of ordinary off‑circuit tap‑changers may lead to voltage‑regulation failures.
e. Prominent harmonic interference from inverters: Grid‑connection of a large number of photovoltaic inverters causes harmonic distortion, which may result in mal‑operation of relay protection and metering deviation and impair power‑generation reliability of the power station.
f. Short‑time short‑circuit shock conditions: High short‑circuit current on the low‑voltage inverter side of PV systems and high short‑circuit current of low‑voltage buses require transformers to possess sufficient dynamic and thermal stability withstand capability.
g. DEWA grid‑connection specification access requirements: DEWA imposes strict grid‑access review for PV step‑up equipment. Complete sets of English test reports and technical documents complying with UAE.S 5010‑1 grid‑connection requirements are mandatory for commissioning.
| Parameter Item | 2.5 MVA‑690/11 kV Three‑Phase Oil‑Immersed Step‑up Transformer | Adaptation Notes for Dubai Desert PV Park Project, UAE |
|---|---|---|
| Rated Capacity | 2.5 MVA | 20 units are distributively deployed in PV array zones. Each unit serves step‑up for one PV sub‑array. Failure of a single unit only affects partial sub‑arrays without causing shutdown of the whole power station |
| Rated Frequency | 50 Hz | Compatible with the 50‑Hz public power grid in UAE. Iron cores and all auxiliary motor components are designed for 50 Hz |
| Rated Voltage Ratio | 690 V / 11000 V (step‑up) | Matches 690 V output of PV inverters and steps up voltage to 11 kV for collection distribution‑grid level |
| Equipment Type | Three‑phase oil‑immersed step‑up transformer | Outdoor installation in desert PV stations with mature and reliable operation & maintenance |
| Voltage Regulation Mode | DE‑type off‑circuit tap‑changer on high‑voltage side, regulation range ±2×2.5%, tap step 2.5% | Supports bidirectional power flow. Tap‑gear adjustment is performed under power‑station shutdown status to adapt to voltage offset of PV stations |
| Cooling Mode | ONAN oil‑immersed natural air cooling | Equipped with 4‑6 radiator groups, each with heat‑dissipation capacity of approx. 31 kW. Heat‑dissipation margin is enlarged for desert sand‑dust and high‑temperature working conditions to ensure full‑load operation under high temperature |
| Vector Group | Dyn11 | Suppresses harmonic currents from PV inverters, mitigates three‑phase unbalance and ensures stable performance of relay protection and metering devices |
| Design Ambient Temperature | Single‑day maximum +45 ℃, annual average maximum 35 ℃, annual average 25 ℃ | Windings, insulation and cooling systems are verified via simulation under extreme high temperature of 45 ℃ with sufficient temperature‑rise margin reserved |
| Winding Material | High‑purity electrolytic copper windings with brazed joints; axially adjustable winding clamping structure | Low loss and excellent thermal conductivity. Current density ≤2.5 A/mm² for high‑voltage winding and ≤1.8 A/mm² for low‑voltage winding, adapting to PV harmonic conditions |
| Insulation Level | HV LI75 kV / AC28 kV; LV AC3 kV; creepage distance of porcelain bushing ≥40 mm/kV, anti‑pollution creepage 50% higher than standard | Withstands lightning and switching over‑voltages in thunderstorm seasons in Dubai and adapts to composite pollution conditions of desert‑coastal areas |
| Short‑circuit Impedance | Impedance voltage between HV‑LV windings: 6.1%; zero‑sequence impedance: 5.5% | Matches short‑circuit level of 11 kV PV collection grid in UAE, balancing voltage quality and short‑circuit current limiting. Short‑time dynamic‑thermal stability: LV busbar 50 kA/3 s, HV busbar 25 kA/3 s |
| Loss Performance (IEC 60076 @75 ℃) | No‑load loss P₀ ≤3.2 kW; load loss Pk ≤28 kW; total loss 31.2 kW; excitation current ≤1% | All factory FAT tests are retested per IEC standards to reduce operational losses of PV stations and improve power‑generation revenue |
| Temperature‑rise Limits | Top‑oil temperature‑rise limit 50 K; maximum allowable hot‑spot temperature of winding 98 ℃ | Adapts to high‑summer temperatures in Dubai, slows insulation aging rate and extends equipment service life |
| Anti‑corrosion Protection Grade | C5‑M heavy‑duty anti‑corrosion grade, tank sealing IP54 | Resists coastal salt‑fog, desert sand‑dust and intense ultraviolet radiation in Dubai. Passes 1000‑hour neutral salt‑spray aging test |
| Base Structure | Flat‑plate base with roller skid and shock‑absorbing structure | Facilitates hoisting, displacement and installation on PV sites and mitigates impact of sand‑wind vibration on internal windings |
| Applicable Standards | IEC 60076 series standards, UAE.S 5010‑1 | Complete English type‑test and factory test reports support DEWA grid‑access review and construction‑site safety acceptance in UAE |
Traditional PV projects procure step‑up transformers in separate batches, which brings duplicated work for drawing design, production scheduling, sea‑freight customs clearance and civil foundation construction, as well as diversified spare‑part models. In this project, 20 transformers adopt unified drawings, are manufactured synchronously and shipped in full container loads directly to Jebel Ali Port:
‑ Distributed sub‑array deployment architecture reduces demand for spare‑equipment civil foundations and saves land acquisition and civil‑engineering investment for PV sites;
‑ Universal radiators, DE off‑circuit tap‑changers, bushings, temperature‑control monitoring modules cut spare‑part inventory by 50%;
‑ Mass production lowers unit manufacturing cost. Compared with scattered phased procurement, overall equipment investment of PV stations can be reduced by 13%;
‑ Complete qualification documents complying with IEC 60076 standards and full‑set English‑language technical documents realize one‑time filing for DEWA grid‑access approval.
During daytime, the Dubai desert PV park generates large‑scale power and feeds energy into the 11 kV grid; at night inverters stop operation and transformers run in no‑load status under bidirectional power‑flow scenarios. Ordinary tap‑changers that are not compatible with bidirectional power may suffer gear offset and poor contact faults.
a. DE‑type off‑circuit tap‑changer is installed on the 11 kV high‑voltage side with ±2×2.5% regulation range (5 tap positions in total). It supports bidirectional power flow. Tap‑gear adjustment is performed under power‑station shutdown to optimize voltage matching between 690 V and 11 kV sides.
b. Dyn11 vector group effectively suppresses harmonic distortion caused by PV inverters, improves three‑phase unbalance and avoids mal‑operation of relay protection and metering deviation faults.
c. 6.1% standard short‑circuit impedance matches short‑circuit current limits of 11 kV PV collection distribution grid in UAE. Dynamic‑thermal stability capability of 50 kA/3 s for low‑voltage busbar and 25 kA/3 s for high‑voltage busbar complies with IEC 60076 short‑circuit withstand standards.
Ambient temperature reaches 45 ℃ in summer at Dubai PV sites, while ground surface temperature rises further under solar radiation. Sand‑dust in desert areas tends to clog radiators. Conventional ONAN transformers may trigger over‑temperature alarms, resulting in disconnection of PV sub‑arrays and power‑generation loss.
a. ONAN oil‑immersed natural air‑cooling system is fitted with 4‑6 radiator groups (approx. 31 kW heat dissipation per group). Heat‑dissipation margin is enlarged for desert high‑temperature conditions.
b. Both high‑voltage and low‑voltage windings adopt high‑purity electrolytic copper with brazed joints and axially clamped winding structure for excellent thermal conductivity. Current density is controlled ≤2.5 A/mm² for HV windings and ≤1.8 A/mm² for LV windings. No‑load loss ≤3.2 kW and load loss ≤28 kW at 75 ℃ are strictly controlled to cut operational losses of power stations.
c. Insulation system adopts Class‑A oil‑impregnated insulating paper. Tap‑change leads are equipped with paper‑insulated sleeves. Iron‑core fasteners are insulated by epoxy resin, glass‑fiber side plates and anti‑rust varnish for laminations.
d. Antioxidant mineral insulating oil complying with IEC 296:1969 is filled, resisting sludge formation under intense solar exposure. 300‑L conservator accommodates oil‑volume variation caused by huge day‑night temperature difference in desert areas. Continuous rated‑load long‑term operation is guaranteed under extreme 45 ℃ ambient temperature to prevent over‑temperature disconnection during PV peak‑generation periods.
Dubai PV park faces combined desert‑gulf coastal environment: salt‑laden air, frequent desert sand‑storms and large day‑night temperature differences easily trigger internal tank condensation and water seepage, leading to deteriorated internal insulation, tank corrosion and oil leakage.
a. Tank wall thickness ≥6 mm, base‑plate thickness ≥8 mm, radiator steel‑plate thickness ≥1.2 mm. High‑strength steel plates are adopted for tanks and radiators. Multi‑layer anti‑corrosion coating is applied: sand‑blasting treatment, epoxy zinc‑rich primer, epoxy intermediate paint and weather‑resistant polyurethane topcoat. It passes 1000‑hour neutral salt‑spray test to resist ultraviolet radiation, salt‑fog and sand‑dust erosion.
b. IP54 all‑weather sealing protection for complete unit. Multi‑layer aging‑resistant cork‑neoprene rubber sealing gaskets are used for flanges and bushing bases to block sand‑dust, salt‑fog and water vapor from entering the tank.
c. 150‑L oil‑level variation capacity of large‑volume conservator accommodates drastic day‑night temperature swings. High‑voltage porcelain bushings feature reinforced external anti‑pollution insulation with creepage distance 50% higher than standard values for composite desert‑coastal pollution scenarios.
d. Flat‑plate base fitted with roller skid and shock‑absorbing structure mitigates sand‑wind vibration impact, protects internal winding clamping assemblies and reduces component‑loosening faults induced by vibration.
Full‑unit insulation impulse withstand, loss and temperature‑rise tests follow IEC 60076 series standards, satisfy UAE.S 5010‑1 distributed‑generation grid‑connection specifications of DEWA and comply with ESMA product‑access requirements in UAE.
a. Insulation of high‑voltage bushings is customized for local lightning‑overvoltage levels to withstand lightning surges in thunderstorm seasons in desert areas.
b. Dual earth terminals are arranged on the tank. Earthing scheme complies with on‑site electrical‑safety earthing codes in UAE.
c. 50‑Hz electrical components including Buchholz relay, pressure‑release valve and PT100 oil‑temperature sensors are adopted. Temperature‑control panel provides English‑language operation interface.
d. Factory FAT and type‑test certificates are fully provided in English for direct submission to DEWA authorities and supervisors for grid‑connection acceptance in UAE.
Case 1: Riyadh desert PV sub‑array project, Saudi Arabia. 16 units of 2.2 MVA transformers of the same ONAN step‑up series are deployed. Maximum site ambient temperature reaches 46 ℃ under desert sand‑dust conditions with minor salt‑fog impact from coastal areas. After commissioning:
a. Stable oil temperature of equipment during summer peak PV generation without over‑temperature disconnection; power output of PV sub‑arrays is secured.
b. Dyn11 vector group delivers satisfactory harmonic suppression for inverter‑generated harmonics with no mal‑operation of protection devices.
c. C4 anti‑corrosion coating ensures no tank corrosion or oil leakage after long‑term desert sand‑wind operation; on‑site O&M workload drops by 55%.
Case 2: Coastal PV power‑station project in Oman. Prominent salt‑fog corrosion environment. Same‑series models with C5‑M heavy‑duty anti‑corrosion are selected. After three‑year operation, no tank corrosion or oil leakage occurs under salt‑fog conditions; no obvious external‑insulation flashover on bushings. Annual inspection by local power utility is successfully passed.
Case 3: Distributed PV project on suburban sites in Qatar. Multiple distributed step‑up transformers are deployed. Fan‑free ONAN natural‑air‑cooling design reduces fan failures caused by sand‑dust and lowers spare‑part replacement frequency on‑site, gaining recognition from EPC contractors.
Technical team conducts multi‑round simulation calculation on electromagnetic performance, temperature rise, anti‑corrosion and over‑voltage performance targeting working conditions of Dubai PV park: 45 ℃ high‑temperature solar exposure, desert sand‑dust, coastal salt‑fog, bidirectional power flow, IEC 60076 and DEWA‑UAE.S 5010‑1 grid‑connection specifications.
a. 50‑Hz dedicated iron‑core electromagnetic optimization; temperature‑rise margin calculation under 45 ℃ extreme ambient temperature; iron‑core flux density controlled at 1.63 Tesla.
b. C5‑M heavy‑duty anti‑corrosion structural design; enlarged anti‑pollution creepage distance for bushings; UV‑resistant and salt‑fog‑resistant Class‑A insulating materials are selected.
c. 6.1% short‑circuit impedance matched to UAE 11 kV distribution grid; design of DE‑type off‑circuit tap‑changer voltage‑regulation circuit; bidirectional power‑flow capability verification.
d. Production starts after confirmation of IEC energy‑efficiency indexes, container sea‑freight dimensions, C5‑M anti‑corrosion and base shock‑absorbing skid schemes.
Each transformer undergoes routine tests in accordance with IEC standards plus special tests simulating local UAE operating conditions. Products with unqualified loss or temperature‑rise performance are forbidden for shipment.
a. Basic routine tests: DC resistance, ratio‑vector test, no‑load loss, load loss, short‑circuit impedance, power‑frequency withstand voltage, lightning impulse LI, full‑stroke verification of DE tap‑changer.
b. High‑temperature‑condition simulation: temperature‑rise simulation verification under 45 ℃ ambient temperature; 24‑hour full‑load continuous temperature‑rise monitoring.
c. Environmental‑durability special tests: 1000‑hour neutral salt‑spray aging test, IP54 dust‑&‑water‑proof verification, UV‑resistance coating aging test.
d. Short‑circuit withstand verification: dynamic‑thermal stability test at 50 kA/3 s for LV side and 25 kA/3 s for HV side to verify fault‑withstand capability of windings and tanks.
e. Auxiliary‑system linkage test: full‑function test of oil‑temperature monitoring, gas protection and over‑temperature alarm.
Equipment components adopt nitrogen‑sealed anti‑rust packaging. Tanks, high‑voltage bushings and tap‑changers are individually protected against moisture for container sea‑freight export. IEC‑standard technical documents, English drawings and complete test reports are prepared in advance for UAE customs clearance. Large‑cargo port hoisting and inland heavy‑haul transport permits are arranged. Temperature‑humidity recorders are fitted during transportation for moisture‑proof monitoring.
20 units are produced and shipped synchronously. Custom factory production cycle: 65 days; sea‑freight duration: 35‑42 days. Total lead‑time to reach construction site of Dubai PV park is approx. 115 days. Production schedule can be flexibly adjusted according to civil‑engineering progress of PV stations; expedited solutions are available.
a. Tri‑party joint unpacking acceptance: Owner, DEWA supervisor and our Middle‑East resident engineers jointly verify integrity of tanks, bushings and sealing components.
b. On‑site positioning and reinforcement of shock‑absorbing base; completion of full‑station earthing system complying with UAE on‑site electrical‑safety specifications.
c. On‑site electrical retests: insulation resistance, transformation ratio, tap‑changer operation verification, protection linkage test. English‑language on‑site SAT test records recognized by DEWA are issued.
d. 48‑hour no‑load trial operation; graded load‑connection to 11 kV collection grid for commissioning and putting‑into‑service of PV sub‑arrays.
a. Deliver complete English drawings, FAT factory‑test reports, IEC type‑test qualifications, PV‑station O&M manuals and operation guidelines for high‑temperature, salt‑fog and sand‑dust operating conditions.
b. Free hands‑on operational training: high‑temperature patrol inspection, DE off‑circuit tap‑changer maintenance, transformer‑oil DGA testing, temperature‑control fault troubleshooting, inspection key points for equipment under sand‑dust and salt‑fog environment.
c. Local spare‑part warehouse in UAE. Conventional spare‑parts including tap‑changers, sealing components and temperature sensors can arrive at sites in Dubai and surrounding PV stations within 10‑18 days to shorten downtime caused by faults.
d. 24‑month full‑unit warranty; lifetime remote technical support. Resident high‑voltage electrical engineers in the Middle East provide on‑site patrol inspection and emergency repair services.
Q1: Under 45 ℃ summer high temperature plus desert sand‑dust in Dubai, will ONAN natural‑air‑cooled transformers overheat and trip off‑grid under full‑load conditions?
A: This model is electromagnetically optimized per IEC 60076, equipped with 4‑6 radiator groups with enlarged heat‑dissipation margin for desert high‑temperature conditions. 45 ℃ high‑temperature temperature‑rise simulation and long‑duration temperature‑rise tests are completed at factory. Multi‑protection of oil‑temperature and winding‑temperature measurement is fitted with over‑temperature alarm function to minimize risks of PV sub‑array over‑temperature disconnection.
Q2: Can the equipment pass DEWA grid‑connection acceptance and on‑site safety acceptance in UAE?
A: Type‑test and factory FAT reports strictly follow IEC 60076 series standards and satisfy UAE.S 5010‑1 distributed‑generation grid‑connection specifications. All technical documents are provided in English. Anti‑corrosion, earthing and insulation structures comply with local safety codes of UAE. Documents can be directly used for tendering, grid‑access filing and on‑site supervisor acceptance.
Q3: What is the overall delivery cycle for the complete set of 20 units?
A: 65 days for custom factory production plus 35‑42 days sea‑freight. Total lead‑time to construction site of Dubai PV park is approx. 115 days. Production schedule can be adjusted according to project milestones and expedited delivery solutions are available.
Q4: Is this step‑up transformer suitable for PV bidirectional‑power‑flow operating conditions?
A: DE‑type off‑circuit tap‑changer is configured to support bidirectional power flow. Dyn11 vector group delivers excellent harmonic‑suppression performance. 6.1% short‑circuit impedance matches 11 kV PV collection grid in UAE. Multiple desert PV projects in the Middle East have been successfully implemented.
This complete‑set solution of 20 units of 2.5 MVA‑690/11 kV oil‑immersed step‑up transformers fully covers sub‑array step‑up and collection scenarios for large‑scale desert PV power plants in Dubai. It delivers an all‑in‑one solution for seven core industry challenges: extreme high‑temperature solar exposure in summer, desert sand‑dust clogging heat‑dissipation, coastal salt‑fog & condensation corrosion, PV bidirectional power flow, inverter harmonic interference, short‑circuit shock and DEWA grid‑access compliance.
Hengfengyou Electric (sales@hfy-transformer.com) is well‑versed in IEC 60076, UAE.S 5010‑1 and full DEWA PV grid‑connection specifications. Custom‑built oil‑immersed step‑up transformers of full capacity for 690 V‑11 kV / 33 kV are available for newly‑built PV stations, solar‑storage projects and commercial‑industrial distributed‑PV EPC projects in UAE. Middle‑East local power groups, international EPC contractors and foreign‑trade suppliers are welcome to obtain detailed technical quotations, complete English qualification documents and type‑test reports.
