What is an Oil-Immersed Transformer?

What is an Oil-Immersed Transformer?

Anoil-immersed transformer is a power transformer that usesinsulating oil (mineral oil or synthetic ester) for bothশীতল এবংelectrical insulation. The core and windings are submerged in oil, which dissipates heat and prevents electrical breakdown.

                          14_副本

Key Components

  1. কোর: Laminated silicon steel to reduce eddy current losses.

  2. উইন্ডিংস: Copper or aluminum conductors (HV/LV).

  3. Tank: Sealed steel container filled with oil.

  4. Insulating Oil:

    • Mineral oil (most common).

    • Bio-based or synthetic ester (eco-friendly alternatives).

  5. Cooling System:

    • Radiators/fins (ONAN – Oil Natural Air Natural).

    • Fans (ONAF – Oil Natural Air Forced).

  6. Protection Devices:

    • বুখোলজ রিলে (gas detection for internal faults).

    • Pressure relief valve.

    • Temperature sensors (oil/winding).

Types of Oil-Immersed Transformers

  1. Hermetically Sealed

    • Fully sealed tank (no oil exposure to air).

    • No conservator; low maintenance.

  2. Conservator-Type

    • Expansion tank (conservator) with breather to absorb moisture.

    • Common in large transformers.

  3. Step-Lap Core Design

    • Reduced no-load losses and noise.

  4. Specialty Types:

    • Fire-resistant (less-flammable oil).

    • Underground (compact design).12

সুবিধা

✔ উচ্চ দক্ষতা: Oil provides excellent heat dissipation.
✔ Long Lifespan: সঠিকভাবে রক্ষণাবেক্ষণ করা হয়েছে, lasts 25-30 বছর.
✔ খরচ-কার্যকর: Lower initial cost than dry-type transformers.
✔ ওভারলোড ক্ষমতা: Handles temporary overloads better.

অসুবিধা

✖ Fire Risk: তেল দাহ্য (requires fireproof barriers).
✖ রক্ষণাবেক্ষণ: Regular oil testing and leak checks needed.
✖ Environmental Concerns: Oil disposal and spill risks.

অ্যাপ্লিকেশন

  • Power Distribution: Step-down 11kV/33kV to 400V.

  • Industrial Plants: স্টিল মিলস, chemical factories.

  • Renewable Energy: Wind/solar farm substations.

  • Railways: Traction power supply.

Maintenance Requirements

  1. Oil Testing:

    • Dielectric strength (>30 kV for mineral oil).

    • Acidity (<0.1 mg KOH/g).

    • Moisture content (<20 ppm).

  2. Leak Inspection: Check gaskets, welds, and valves.

  3. Sludge Removal: Clean oil ducts periodically.

মান & Certifications

  • আইইসি 60076: International standards.

  • IEEE C57.12.00: North American standards.

  • GB/T 6451: Chinese standards.

Oil-Immersed vs. ড্রাই-টাইপ ট্রান্সফরমার

Feature

তেল-নিমজ্জিত

শুষ্ক-টাইপ

কুলিং

তেল

Air/Solid Insulation

Fire Risk

Higher

Lower

রক্ষণাবেক্ষণ

More frequent

Minimal

কর্মদক্ষতা

Better at high loads

Slightly lower

Cost

Lower initial cost

Higher

Purchasing Considerations

  1. ক্ষমতা (কেভিএ): Match to load requirements.

  2. Voltage Ratio: Input/output voltage levels.

  3. Impedance: Typically 4–10% for distribution transformers.

  4. Environment: Indoor/outdoor, তাপমাত্রা, আর্দ্রতা.

  5. Certifications: Ensure compliance with local regulations.

FAQ

প্র: Can oil-immersed transformers be used indoors?
ক: হ্যাঁ, but require fireproof vaults and ventilation (NFPA 70 rules).

প্র: How often should oil be tested?
ক: Annually for routine checks; after overloads or faults.

প্র: Are biodegradable oils reliable?
ক: হ্যাঁ, synthetic esters offer similar performance with lower fire risk.

For acustomized selection, provide:

  • Load details (কেভিএ, ভোল্টেজ).

  • Installation environment.

  • Special requirements (যেমন, কম শব্দ, high efficiency).

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