Caption: Supply of two custom-designed 33kV dry-type step-up transformers for a major solar photovoltaic plant in the Abu Dhabi desert, enabling efficient and reliable power transmission from inverter stations to the medium voltage collection grid under extreme environmental conditions.
Client: UAE Utility-Scale Solar PV Developer
Location: Abu Dhabi Desert Region, UAE
Application: LV to MV power conversion for solar photovoltaic generation
Installation: Indoor (Climate-Controlled Transformer Chamber)
Quantity: 2 Units
Core Function: Transform 690V AC output from central inverters to 33kV for grid injection via the plant's MV collection system.
Electrical Parameters:
Rated Power: To be determined per inverter array capacity (Custom Design)
Input Voltage (LV): 690 V
Output Voltage (MV): 33,000 V
Frequency: 50 Hz
Vector Group: Dyn11
Impedance (Ucc): 6% (Optimized for fault level coordination)
Winding Material: Primary & Secondary - Copper (CU)
No-Load Loss (Guaranteed): ≤ 2900 W
Load Loss: Per customer specification, optimized for typical solar load profile.
Design & Construction:
Type: Three-Phase, Air-Insulated (Dry-Type), Cast Resin or VPI (Vacuum Pressure Impregnated) technology.
Cooling: ANAN (Air Natural Air Natural) for indoor installation. Forced air cooling (ANAF) capability can be provided for optional overload capacity.
Insulation System: Class F or H (180°C or 220°C) temperature rating, designed for a maximum ambient temperature of 50°C.
Taps: Off-Circuit Tap Changer (OCTC) on HV winding: ±5% in 2.5% steps (5 positions).
Protection: Integral temperature sensors (PT100/PTC) in all three phases of LV & HV windings for direct input to protection relay.
Mechanical & Safety:
Enclosure: IP20 standard (indoor). IP23 or higher available for dust protection.
Fire Safety: Flame-retardant, self-extinguishing resin system. No flammable liquids, suitable for indoor installation without special fire suppression vaults.
Grounding: Equipped with minimum two robust, easily accessible grounding terminals sized for full fault current.
1. Solar-Generation Optimized Design
Low No-Load Losses: Guaranteed ≤2900W minimizes energy consumption during nighttime and low-irradiance periods, crucial for plant yield (Performance Ratio).
Inrush Current Management: Special design features (e.g., stepped core design, controlled magnetic flux) limit inrush current to <8x rated current, protecting inverter IGBTs and reducing stress on LV switchgear.
Non-Linear Load Compatibility: Designed to handle harmonic currents (up to specified THDi) from inverters without excessive overheating, using appropriate winding and core construction.
2. Extreme Climate Resilience (Desert Environment)
High-Temperature Endurance: Insulation system designed for a 50°C ambient with appropriate thermal derating considered. Cooling airflow path is optimized to prevent hot spots.
Dust & Humidity Resistance: Sealed windings (Cast Resin) or impregnated windings (VPI) are immune to moisture and dust ingress. Enclosure design ensures minimal dust accumulation on critical parts.
Corrosion Protection: All metallic parts (core clamps, brackets, enclosure) feature anti-corrosion treatment suitable for arid, potentially corrosive desert atmospheres.
3. Enhanced Safety & Intelligent Monitoring
Integrated Protection: Pre-wired for connection to a dedicated Protection Relay (e.g., DMCR type) providing comprehensive protection: over-temperature (two-stage alarm/trip), overtemperature differential, and optional pressure monitoring (for sealed units).
Thermal Management: Advanced thermal modeling ensures even heat distribution. Continuous temperature monitoring allows for predictive load management.
Safety: No oil eliminates risk of fire, leakage, and environmental contamination. Fully enclosed live parts ensure operator safety.
4. Reliability & Ease of Integration
Grid Compatibility: 33kV output directly interfaces with UAE standard MV collection networks (often 33kV). Impedance value is coordinated with grid and inverter fault levels.
Modular & Service-Friendly: Lightweight compared to oil-filled units. Windings are easily inspectable. Minimal maintenance required.
Low Noise Level: Designed to meet strict indoor noise requirements, often <70 dB(A).
Customization & Testing:
Design tailored to specific inverter make/model and LV cable configuration.
Factory tests include routine tests per IEC 60076-11, plus special tests: Lightning Impulse (LI)test for 33kV level, temperature rise test, and harmonic loss evaluation.
Witnessed testing available for key performance guarantees (losses, impedance, sound level).
Standards & Certification:
Fully compliant with IEC 60076-11 (Dry-Type Transformers).
Meets DEWA (Dubai) / ADDC (Abu Dhabi) / FEWA (Federal) technical guidelines as applicable.
Conforms to IEC 61869, IEC 60721 (for environmental conditions).
CE Marking provided.
No-Load Loss (Po): ≤ 2900 W
Load Loss (Pk): As per contract, at rated current and reference temperature.
Impedance Voltage (Ucc): 6% (±7.5% tolerance as per standard)
Temperature Rise: Guaranteed not to exceed specified limits (e.g., 100K for Class F) at rated load and 50°C ambient.
Efficiency: Calculated efficiency curve over typical solar load profile (25%-100%) will be provided, demonstrating high efficiency at partial loads common in PV operation.
