Dielectric loss tester ideal insulating medium behaves as pure capacitance



Dielectric loss tester is a specialized instrument used to measure the insulation performance of high-voltage electrical equipment. It evaluates the insulation status of the equipment by precisely measuring the dielectric loss factor (tanδ) and capacitance (Cx) of the insulating material, determining whether there are defects such as moisture, aging, or deterioration.

This type of instrument is widely used in field tests, preventive tests, and equipment acceptance inspections in power systems, power plants, and substations.

⚙️ Working Principle

Under the action of AC voltage, an ideal insulating medium behaves as pure capacitance, with the current leading the voltage by 90°. However, due to the presence of conductance and polarization losses in actual insulating materials, the angle by which the current leads the voltage is less than 90°, and the difference δ is the dielectric loss angle.

The dielectric loss factor tanδ is the tangent of this angle, and it is a key parameter for measuring the energy loss of insulating materials. The larger the tanδ value, the greater the insulation loss and the poorer the insulation performance.

Modern dielectric loss testers generally adopt digital sampling technology, applying high voltage to the test object while collecting voltage and current signals, and accurately calculating tanδ and capacitance Cx through high-speed computation.