National Thermal Power Corporation (NTPC), India’s largest energy conglomerate, recently announced the unveiling of a 75 MW capacity floating solar PV installation in Kayakullum, Kerala. The floating solar PV project at Kerala uses 16 free-breathing transformers rated at 5MVA/33kV, manufactured in India by Toshiba. The electrical system was designed and installed by Tata Power.

Floating solar is a relatively new development in the renewable energy world. The immediate advantages are clear; floating solar uses less costly real estate, so the surrounding land can be used for agriculture or commercial purposes. In addition, the water acts as an effective cooling agent that can improve PV panel performance. However, floating solar arrays are subject to heightened external stresses. Specifically, exposing components such as transformers to air and water increases risk of corrosion and rust, leading to the transformer insulating fluid being exposed to air.

In the Kerala project, the area’s high humidity provided an added challenge for the transformers’ optimum operation. High ambient temperatures also accelerate the oxidation process adding further engineering risk.

MIDEL 7131 synthetic organic ester was chosen over natural ester because of its proven performance in free-breathing transformers (with its high oxidation stability). MIDEL 7131 is also biodegradable and non-toxic to aquatic life – a major consideration for any floating PV installation; if any leaks were to occur, the fluid presents a minimal contamination profile in relation to the surrounding land and water.

“Floating solar PV projects present specific engineering challenges. Using MIDEL 7131 synthetic organic ester rather than a natural ester removes transformer risk and future-proofs the project’s power system, giving the operator peace of mind for proven performance.”
– Amit Kumar, Business Development Manager, MIDEL India, SAARC, Myanmar and Thailand

Damage to system components by wildlife is a recognised challenge in floating solar plants. If such damage were to cause a short circuit and start a blaze in other components, MIDEL 7131 fluid would not contribute to such a fire because of its high fire point and 100% safety record. Also, MIDEL 7131 filled transformers can be installed as per IEC 61936 with less protection enabling end-users to resolve practical challenges and reducing costs of traditional protection systems at these critical locations.

MIDEL 7131 has the following proven advantages as a synthetic organic ester transformer dielectric fluid:

The highest fire safety rating (K3, >300°C fire point and net calorific value of <32MJ/kg), fully/readily biodegradable, high oxidation stability, superior moisture tolerance (protecting the transformer’s solid insulation and thereby extending its lifetime), and is compliant with BIS 16081, 16099 and 13503.

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