IEC 60076 Distribution Transformer for BESS Energy Storage System 2000kVA 35kV Class with 0.69kV Primary
Transformateur 2000kVA conforme à la norme CEI 60076 pour les systèmes BESS. Gère le flux de puissance bidirectionnel, les harmoniques élevées (facteur K ≥13) et le chargement cyclique. Comprend de faibles pertes à vide, un refroidissement ONAN et des options personnalisées pour l'intégration au réseau.
0.69kV BESS Energy Storage System Transformer
,2000kVA BESS Energy Storage System Transformer
This IEC 60076 compliant liquid-immersed step-up transformer is purpose-engineered for Battery Energy Storage System (BESS) grid interconnection applications. Rated at 2000kVA with a 35kV Class high-voltage side and 0.69kV low-voltage primary, the unit serves as the critical interface between the Power Conversion System (PCS) and the medium-voltage utility grid. Unlike conventional distribution transformers designed for steady industrial loads, this transformer is built to handle the unique electrical and thermal stresses inherent to energy storage operations—including bidirectional power flow, high harmonic content, aggressive charge/discharge cycling, and extended periods of partial load energization. It delivers reliable voltage transformation and electrical isolation while maintaining long-term operational stability in demanding renewable energy environments.
Harmonic-Tolerant Design with K-Factor ≥ 13 – Engineered to withstand the elevated harmonic currents generated by inverter-based PCS equipment during rapid charge/discharge cycles. The winding and core design prevents excessive eddy current losses and abnormal temperature rise, ensuring stable operation under non-sinusoidal load conditions without premature insulation aging.
Full Compliance with IEC 60076 Series – Manufactured and tested in accordance with IEC 60076 standards for power transformers, covering general requirements, insulation levels, temperature rise limits, and energy efficiency parameters. Routine and type test protocols validate performance consistency across every unit.
Bidirectional Power Flow Capability – Designed for seamless energy transfer in both charging (grid to battery) and discharging (battery to grid) modes. The electrical configuration supports the dynamic reversal of power direction without compromising insulation integrity or thermal stability.
Optimized for Cyclic Loading & Partial Load Operation – Unlike standard transformers that perform best under steady-state conditions, this unit accommodates the aggressive load cycling and extended low-load energization periods typical of BESS duty cycles, reducing long-term thermal degradation.
High-Efficiency Core with Low No-Load Losses – Built with premium grain-oriented silicon steel core materials to minimize core losses. In energy storage applications where the transformer may remain energized for extended periods even at low or zero throughput, reduced no-load losses translate directly to improved project IRR and lower lifetime operational costs.
| Parameter | Specification |
|---|---|
| Rated Capacity | 2000 kVA |
| Primary Voltage (LV Side) | 0.69 kV (690V) |
| Secondary Voltage (HV Side) | 35 kV Class |
| Phases | Three Phase |
| Rated Frequency | 50 Hz / 60 Hz (configurable) |
| Vector Group | Dyn11 (standard) / Custom available |
| Cooling Method | ONAN (Oil Natural Air Natural) |
| Applicable Standard | IEC 60076 Series |
| Tap Changer | Off-Circuit / On-Load (optional) |
| Winding Material | Copper / Aluminum (customer-specified) |
| Temperature Rise | Oil: 60K max; Winding: 65K max |
| Altitude | ≤ 1000m (higher altitudes available upon request) |
| Ambient Temperature | -25°C to +40°C (extended range optional) |
| Parameter | Value |
|---|---|
| No-Load Loss | ≤ 1.8 kW (typical at 50Hz) |
| Load Loss (at 75°C) | ≤ 14.5 kW (typical at 50Hz) |
| Impedance Voltage | 6.0% ± 10% |
| Insulation Level (HV) | LI 200 kV / AC 70 kV |
| Insulation Level (LV) | LI 60 kV / AC 25 kV |
| Harmonic Tolerance | K-Factor ≥ 13 |
| Partial Discharge Level | ≤ 50 pC at 1.2Ur |
- Routine Tests (IEC 60076): winding resistance measurement, voltage ratio and phase displacement check, impedance voltage and load loss measurement, no-load loss and current measurement, dielectric routine tests (applied voltage test, induced voltage test)
- Type Tests (IEC 60076): temperature rise type test (IEC 60076-2), dielectric type tests (IEC 60076-3)
- Optional Special Tests: partial discharge measurement, sound level determination (IEC 60076-10), frequency response analysis
- Corrugated tank design with optimized cooling surface area for enhanced heat dissipation
- Hermetically sealed or conservator-type tank options available
- High-grade mineral oil insulation with optional biodegradable ester fluid alternatives
- Robust core clamping system with high-density electrical laminated wood components to suppress stray flux losses
- Heavy-duty external coating for outdoor installation with corrosion protection
BESS inverters generate substantial harmonic currents during switching operations, which increase eddy current losses and can cause abnormal temperature rise, accelerated insulation aging, and gassing issues in standard transformers.
Our Solution: This transformer is designed with harmonic-aware engineering principles. Increased conductor cross-section, reduced current density, and optimized winding geometry mitigate the thermal impact of harmonic penetration. The unit supports K-Factor ≥ 13 loading, ensuring it can safely handle the harmonic spectrum typical of BESS charge/discharge cycles without requiring aggressive de-rating.
Unlike continuous industrial loads, BESS applications subject transformers to rapid transitions between charging (grid to battery) and discharging (battery to grid) modes, creating dynamic thermal loading conditions that stress insulation systems over time.
Our Solution: The cooling system and insulation materials are selected specifically for cyclic duty. ONAN cooling provides reliable heat dissipation without auxiliary power requirements. The corrugated tank wall design maximizes surface area for natural convection cooling, while thermal class materials are rated to withstand repeated temperature excursions without degradation.
Energy storage systems require transformers that perform equally well in both power flow directions—stepping up from 0.69kV to 35kV during discharge, and stepping down during charging. This dual-function operation demands symmetrical electrical characteristics.
Our Solution: The Dyn11 vector group configuration provides stable voltage transformation and phase relationship in both power flow directions. The transformer delivers the same impedance and efficiency characteristics regardless of whether energy is flowing toward the grid or toward the storage system, ensuring consistent system performance across all operational modes.
BESS transformers often remain energized for long durations even when the storage system is idle, waiting for dispatch signals or market conditions. During these periods, no-load losses become the dominant factor in overall energy consumption.
Our Solution: The transformer incorporates a premium grain-oriented silicon steel core that minimizes no-load losses compared to conventional distribution transformer designs. This reduces standby energy consumption and improves overall project efficiency metrics—a critical factor for developers focused on lifecycle operating costs and sustainability reporting.
The high-frequency switching waveforms from PCS equipment can contribute to elevated partial discharge activity, particularly in 35kV class windings, potentially accelerating insulation degradation over the transformer's service life.
Our Solution: The winding insulation system is designed and manufactured with enhanced partial discharge control measures. Quality assurance protocols include partial discharge testing on representative units, with verification that PD levels remain within industry-accepted limits under operating voltage conditions, contributing to long-term insulation reliability.
A: BESS inverters generate non-sinusoidal current waveforms with significant harmonic content during charge/discharge cycles. These harmonics increase eddy current losses and winding heating beyond what a standard transformer can safely handle. A K-Factor rating indicates the transformer's ability to tolerate harmonic loading without overheating. For BESS applications with high harmonic content, a K-Factor of 13 to 20 is recommended. This 2000kVA transformer is engineered with K-Factor ≥ 13 capability, ensuring safe operation without requiring aggressive de-rating under typical BESS harmonic spectra.
A: ONAN (Oil Natural Air Natural) cooling relies on natural convection of oil within the tank and natural air circulation around the tank surface to dissipate heat—no fans or pumps are required. This passive cooling method is highly reliable, requires zero auxiliary power, and minimizes maintenance needs. For a 2000kVA transformer in outdoor BESS applications, ONAN cooling is entirely sufficient provided the tank is properly sized with adequate cooling surface area (corrugated wall design). The transformer is engineered with thermal margins that accommodate the cyclic loading profile typical of energy storage duty cycles.
A: This transformer is designed with symmetrical electrical characteristics in both power flow directions. The Dyn11 vector group configuration ensures stable voltage transformation whether the unit is stepping up (0.69kV to 35kV during discharge) or stepping down (35kV to 0.69kV during charging). The key factors affecting lifespan are not the direction of power flow itself, but rather the harmonic content and thermal cycling associated with BESS operation. Our design addresses these factors through harmonic-tolerant winding design, robust insulation systems, and thermal management optimized for cyclic duty, ensuring expected service life comparable to similar-rated transformers in conventional applications.
A: Each unit undergoes comprehensive routine testing in accordance with IEC 60076, including winding resistance measurement, voltage ratio and phase displacement verification, impedance voltage and load loss measurement, no-load loss and current measurement, and dielectric routine tests (applied voltage test and induced voltage test). Type tests available upon request include temperature rise type testing per IEC 60076-2 and dielectric type tests per IEC 60076-3. Additionally, optional special tests such as partial discharge measurement and sound level determination per IEC 60076-10 can be performed based on project specifications.
A: Grid connection requirements vary by utility and jurisdiction, but typically include specifications for voltage tolerance, frequency tolerance, power factor capability, harmonic distortion limits, and fault ride-through performance. This transformer serves as the voltage interface between the PCS and the utility network, and its electrical parameters—including 6.0% impedance voltage and Dyn11 vector group—support stable grid integration. For project-specific compliance documentation (such as harmonic and distortion content at the point of common coupling), we recommend coordination between the transformer manufacturer, PCS supplier, and EPC contractor to ensure the complete system meets all utility interconnection standards.
A: Yes. The transformer can be configured for integration into compact, containerized substation solutions commonly used in modern BESS projects. Options include pad-mounted enclosure configurations, compact footprint designs for skid mounting, and appropriately rated cable termination compartments compatible with containerized system layouts. Customized enclosure dimensions and termination configurations are available to meet specific project integration requirements—please contact our technical team with your installation constraints for a tailored proposal.
