What Is the Dissipation Factor (DDF)?
DDF (or Tan δ) is a measure of electrical energy lost as heat in insulating oil when subjected to an alternating electric field. A higher DDF indicates contamination by moisture, oxidation products, or conductive particles, leading to reduced insulation performance and increased risk of partial discharges.
What Is Volume Resistivity?
Volume resistivity indicates the oil’s resistance to electrical conduction under a DC field. Lower resistivity values suggest the presence of polar contaminants and conductive impurities that may reduce oil effectiveness and compromise transformer reliability.
Test Standard - IEC 60247
Insulating Liquids – Measurement of Relative Permittivity, Dissipation Factor (Tan δ) and DC Resistivity.
| Parameter | New Oil | In-Service Oil | Alarm Limit |
|---|---|---|---|
| Dissipation Factor (90°C) | ≤ 0.005 | ≤ 0.01 | > 0.05 |
| Resistivity (Ω·m @ 90°C) | ≥ 10¹² | ≥ 10¹⁰ | < 10⁹ |
Why DDF & Resistivity Testing Matters
- Detects early signs of oil deterioration
- Assesses contamination by water, acids, or polar substances
- Predicts dielectric failures and partial discharges
- Helps determine oil filtering or replacement needs
- Improves insulation system life and asset safety
Our Sample-to-Report Workflow
- Vacuum-based sample collection with barcode tracking
- High-accuracy test cells with temperature control
- Automated DDF & Resistivity measurements at 90°C
- Data fed into ERP system with trend analysis
- Final report with condition grading and recommendations
Why Choose Tru-FIL for IFT Testing?
- Fully compliant with IEC 60247 & ISO/IEC 17025
- AI-integrated ERP for instant results and alerts
- Clean-room calibrated lab conditions for high repeatability
- Pan-India vacuum sampling with digital chain-of-custody
- 24/7 lab operations for continuous support
Report Deliverables
- DDF/Tan Delta (%) at specified temperature
- Volume resistivity (Ω·m) with reference temperature
- Severity classification (Normal / Alert / Alarm)
- AI-generated maintenance suggestions
- Historical comparisons (if applicable)