O que é um transformador imerso em óleo?

O que é um transformador imerso em óleo?

Umtransformador imerso em óleo is a power transformer that usesinsulating oil (óleo mineral ou éster sintético) for bothresfriamento eelectrical insulation. O núcleo e os enrolamentos estão submersos em óleo, which dissipates heat and prevents electrical breakdown.

Key Components

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

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

3. Tanque: 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:

• Revezamento Buchholz (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 (design compacto).

Vantagens

✔ Alta eficiência: Oil provides excellent heat dissipation.
✔ Longa vida útil: Properly maintained, lasts 25-30 anos.
✔ Econômico: Lower initial cost than dry-type transformers.
✔ Capacidade de sobrecarga: Handles temporary overloads better.

Disadvantages

✖ Fire Risk: O óleo é inflamável (requires fireproof barriers).
✖ Manutenção: Regular oil testing and leak checks needed.
✖ Environmental Concerns: Oil disposal and spill risks.

Aplicativos

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

• Industrial Plants: Siderúrgicas, chemical factories.

• Energia Renovável: 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.

Standards & Certifications

• CEI 60076: International standards.

• IEEE C57.12.00: North American standards.

• GB/T 6451: Chinese standards.

Oil-Immersed vs. Transformadores do tipo seco

Purchasing Considerations

1. Capacidade (kVA): Match to load requirements.

2. Relação de tensão: Input/output voltage levels.

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

4. Environment: Indoor/outdoor, temperatura, umidade.

5. Certifications: Ensure compliance with local regulations.

Perguntas frequentes

P: Can oil-immersed transformers be used indoors?
UM: Sim, but require fireproof vaults and ventilation (NFPA 70 rules).

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

P: Are biodegradable oils reliable?
UM: Sim, synthetic esters offer similar performance with lower fire risk.

For acustomized selection, provide:

• Load details (kVA, tensão).

• Installation environment.

• Special requirements (por exemplo, baixo ruído, high efficiency).