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Intelligent Grounding Transformer Solution for Large-Scale PV Plants in Vietnam
1. Safety and Compliance Challenges of Grounding Systems in High-Humidity, High-Salinity Environments
In recent years, Vietnam’s solar industry has expanded rapidly—especially in southern coastal provinces like Bình Thuận and Ninh Thuận, where numerous utility-scale photovoltaic (PV) plants exceeding 100 MW have been commissioned. However, these projects face persistent and severe challenges related to grounding system performance.
First, the local climate is characterized by high temperature and humidity, with intense salt spray corrosion along the coast. Conventional oil-immersed grounding transformers are highly susceptible to casing rust, insulation oil degradation, shortened service life, and risks of oil leakage or fire.
Second, Vietnam’s 35 kV distribution networks are predominantly ungrounded, lacking effective mechanisms to suppress single-phase-to-ground faults. Such faults—commonly triggered by lightning strikes, cable aging, or animal intrusion—generate sustained arc-induced overvoltages. These can cause frequent inverter tripping at best, or catastrophic damage to pad-mounted transformer windings or DC-side insulation at worst, resulting in significant equipment losses.
Moreover, Vietnam suffers from a shortage of skilled O&M personnel. In remote sites, fault response times average over 15 hours, severely impacting energy yield and Power Purchase Agreement (PPA) compliance. Compounding the issue, Vietnam’s Ministry of Industry and Trade issued new regulations in 2023 banning mineral-oil-filled equipment in new solar projects and requiring green compliance documentation—accelerating the shift toward dry-type, eco-friendly, and intelligent grounding solutions.
2. Customized Intelligent Dry-Type Grounding System for Tropical Weak Grids
To address these challenges, an intelligent dry-type grounding transformer system—specifically tailored for tropical climates and weak grid conditions—was successfully deployed at the “Sunrise 200 MW” PV plant in Bình Thuận Province.
At its core is a Zig-Zag connected dry-type grounding transformer, featuring:
- An amorphous metal core and H-class epoxy resin vacuum casting;
- IP55-rated enclosure with 316L stainless steel housing and nano-hydrophobic coating, enabling long-term operation under 45°C ambient temperature, 95% relative humidity, and aggressive salt-laden air;
- A 50 Ω stainless alloy neutral grounding resistor, limiting fault current to below 20 A to effectively suppress overvoltages;
- Seamless integration with standard relay protection systems for precise fault line selection, ensuring non-faulted feeders remain online.
To enhance O&M efficiency, the unit integrates fiber-optic temperature sensors and zero-sequence current transformers. Operational data is transmitted in real time via 4G to the local SCADA system and a Vietnamese-language mobile app. Field staff can scan a QR code to view equipment status, while the China–ASEAN Renewable Energy O&M Center (Hanoi) provides 24/7 remote diagnostics—dramatically reducing reliance on highly skilled local technicians.
The entire solution is oil-free and halogen-free, fully compliant with Vietnam’s latest environmental regulations, and has obtained TCVN electrical safety certification.
3. Operational Results and Multi-Dimensional Value: Safety, Economics, and Sustainability
Since commissioning in 2023, the solution has delivered outstanding results at the Sunrise 200 MW plant:
- Annual outages caused by single-phase ground faults dropped from 6.8 to just 0.5;
- Average fault repair time decreased from 16 hours to under 2 hours;
- Inverter failures due to overvoltage fell from 12 units/year to only 1, saving approximately USD 180,000 in direct maintenance costs;
- The project passed Vietnam Electricity (EVN)’s grid interconnection review on the first attempt, accelerating revenue settlement.
Thanks to its green credentials, reliability, and local adaptability, the solution helped the project earn Vietnam’s “Green Energy Demonstration Project” designation and gain inclusion in the Asian Development Bank’s Renewable Energy Financing Program, facilitating future funding.
This model has now been replicated across multiple new solar projects in Vietnam and holds strong potential for expansion into Thailand, the Philippines, and Indonesia—offering a high-quality benchmark for Chinese technology and standards going global.
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