Insulating oil in electrical power apparatus serves two primary roles, as an insulator and a coolant. As an insulating liquid, oil’s most important property is a high dielectric strength and as a cooling liquid, a low viscosity is paramount. The principal nemeses of insulating oil are oxidation, contamination (particularly moisture, which tends to lower the dielectric properties of insulating oil), and excessive temperature. These enemies are managed through design, regimented installation processes and prudent operation of the oil-filled power apparatus. At all stages of a power asset’s life, testing must be conducted to evaluate the condition of the insulating oil. In fact, for some assets, it can be argued that the oil is tested more frequently than any other component.

Tests that are concerned with the immediate condition and acceptability of the insulating oil include dielectric breakdown tests, moisture measurement by the Karl Fischer (KF) method, and dielectric dissipation factor. Megger provides laboratory grade oil test equipment, backed by experience reaching back to the early 20th century, to test these fundamental characteristics of insulating oil.