Transformer oil, also known as insulating oil, is a specialized mineral oil used in transformers for insulation and cooling purposes. It plays a critical role in maintaining transformer performance and longevity.

Functions of Transformer Oil

1. Insulation – Prevents electrical arcing between live parts.

2. Cooling – Dissipates heat generated by the core and windings.

3. Moisture Prevention – Protects against insulation degradation.

4. Arc Suppression – Prevents short circuits and flashovers.

Types of Transformer Oil

1. Mineral Oil:

Most commonly used.

Derived from petroleum (Naphthenic or Paraffinic-based).

2. Silicone-based Oil:

Higher fire resistance.

Used in sensitive environments.

3. Natural Ester (Vegetable-based) Oil:

Biodegradable and eco-friendly.

Good moisture tolerance.

4. Synthetic Ester Oil:

Better oxidation stability than natural ester oils.

Used in high-temperature applications.

Properties of Good Transformer Oil

High Dielectric Strength – Withstands high voltages.

Low Viscosity – Ensures efficient cooling.

High Thermal Stability – Resists oxidation and sludge formation.

Low Moisture Content – Prevents electrical breakdown.

Good Chemical Stability – Maintains performance over time.

Transformer Oil Testing

Regular testing is essential to ensure transformer reliability. Some key tests include:

Dielectric Breakdown Voltage (BDV) Test – Measures insulation strength.

Moisture Content Test – Ensures low water content.

Acid Number Test – Detects oil degradation.

Interfacial Tension Test – Checks oil aging.