Transformer Oil Testing

A Proven Loss Prevention Technique

Transformer oil testing is a key part of any preventive maintenance program and should be conducted on a regular basis. Consider it an early warning system that helps you set priorities, schedule work, arrange for outside services and order parts and materials. The following are some of the most common tests for transformer oil:

Dissolved Gas-In-Oil Analysis

An annual Dissolved Gas-In-Oil Analysis (DGA) is the most important test for transformer oil and can give an early indication of abnormal conditions. As the name describes, this test analyzes the type and quantity of gases dissolved in the oil, using a small sample that is examined in a laboratory. Certain quantities and combinations of gases typically found in the oil can indicate insulation overheating/overloading, liquid overheating, partial discharge (corona) or arcing in the transformer.

Screen Testing

The screen test is a collection of physical, electrical and chemical tests for transformer oil. Typically, a 1 liter sample of oil is collected. No single test alone will indicate the true condition of the liquid, so it is suggested all be performed.

  • Dielectric Breakdown: A physical test that measures the breakdown voltage of an insulation liquid and indicates the presence of contaminating agents.
  • Interfacial Tension: This test of electrical insulating fluids is an indicator of the presence of polar compounds.
  • Color: Oil color indicates aging and presence of contaminants.
  • Acidity: As acid values increase (usually due to oxidation of the oil) the insulating quality of the oil decreases.
  • Power Factor (dissipation factor): This test measures the dielectric losses in the liquid, hence the amount of energy dissipated as heat.

Other Tests

The water content test detects the moisture content in parts per million of the liquid insulation. A test to determine polychlorinated biphenyls (PCBs) on a percentage value, or as a parts-per-million value, is widely available from commercial laboratories.

Loss Prevention Services

As a loss prevention service, Hartford Steam Boiler provides laboratory analysis of insulating fluid for all insured transformers critical to production. HSB also offers companies not insured by HSB tests for insulating oil analysis of transformers, oil circuit breakers (OCBs) and load tap changers (LTCs). HSB provides consulting services and can manage an entire oil testing program, from scheduling to analysis and issuing reports.

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1997 Hartford Steam Boiler Inspection and Insurance Co.