Which is more economical: transformer oil purification or replacement?

Whether to choose oil purification or oil replacement for transformer oil is more economical requires a comprehensive assessment of oil quality, equipment requirements, and long-term costs. The following is a detailed analysis:

Scenario Where Purification is More Economical (Recommended Priority)

1. Mild to Moderate Oil Deterioration

- Conditions: Acid value <0.3mg KOH/g, dielectric loss <2%, moisture <50ppm, and particulate contamination within standards (ISO 4406 ≤18/16/13).

- Method: Use two-stage filtration (coarse filtration + 1-3 micron fine filtration) + vacuum dehydration, resulting in a cost of only 20%-40% of new oil.

- Example: Oil purification for a 220kV transformer costs approximately 15,000 RMB, while oil replacement costs 80,000-100,000 RMB (including oil, labor, and waste oil disposal).

2. High Equipment Compatibility Requirements

- Some imported transformers have special oil certifications (such as Shell Diala and Nynas). Oil replacement may cause compatibility issues, while purification preserves the original additive system.

3. Environmental and Policy Factors

- Purification reduces hazardous waste (HW08) generation, complies with the waste oil recycling incentive policy in HJ 607-2011, and avoids disposal costs (approximately 3,000-5,000 RMB/ton).

Scenario for More Economical Replacement

1. Severe Oil Deterioration

- Indicators: Acid value > 0.5 mg KOH/g, dielectric loss > 5%, deep carbonization, or contamination with irreversible contaminants (such as fuel oil or PCBs).

- Reason: Purification costs can exceed 70% of the price of new oil (if bleaching clay adsorption and multiple filtration steps are required), and performance cannot be fully restored.

2. Small Transformers or Low-Value Oils

- The total cost of oil replacement for transformers with a capacity less than 1000 kVA may be less than 10,000 RMB, while the cost of renting the purification equipment plus labor is approximately 8,000 RMB, making it a poor value for money.

3. Emergency Repair Needs

- Purification takes 6-24 hours, while oil change only takes 2-4 hours (including oil filling and stabilization). Oil change should be prioritized when downtime losses are higher.

Decision-Making Recommendations

1. Test First, Then Decide:

- Test acid value, dielectric loss, moisture, and breakdown voltage. If key indicators are within acceptable limits, prioritize purification.

2. Calculate the Cost Breakdown:

- When purification costs exceed 60% of the new oil price, oil change is more cost-effective.

3. Consider Hidden Costs:

- Purification avoids the new oil break-in period (initial particle release) and reduces transformer insulation risks.

Conclusion:

- In most cases, purification is more economical (saving 40%-80%), especially for high-voltage, large-capacity transformers.

- Exceptions: For severely degraded oil or small equipment, direct replacement is more efficient.

It is recommended to consider the oil refining test report and the criticality of the equipment for a comprehensive judgment.