The dielectric loss tester causes the phase difference between current and voltage to be less than
The dielectric loss tester (often referred to as a loss tangent tester or anti-interference dielectric loss tester) is an "physical examination instrument" used in power systems to evaluate the insulation performance of high-voltage electrical equipment. It sensitively detects distributed defects such as overall moisture absorption and aging deterioration of equipment insulation by measuring the dielectric loss tangent (tanδ) and capacitance (Cx) of insulating materials.
⚡ Core Working Principle
The principle of the dielectric loss tester is based on the energy loss characteristics of dielectrics under an alternating electric field:
Physical basis: An ideal insulating medium is equivalent to a pure capacitor, with current leading voltage by 90°. However, actual insulating materials contain conductance and polarization losses, causing the phase difference between current and voltage to be less than 90°. This small angular difference (δ) is the dielectric loss angle, and its tangent value (tanδ) directly reflects the quality of insulation. The smaller the tanδ value, the better the insulation quality.
Measurement technology: Modern instruments generally adopt fully automatic digital measurement technology. Inside the instrument, a high-voltage power supply applies a sinusoidal voltage to the test object, while simultaneously and synchronously acquiring the current signal flowing through the test object and the reference signal from the standard circuit. Through a microcontroller using digital algorithms such as Discrete Fourier Transform (DFT) or vector operations, the phase difference and amplitude between the two are precisely calculated, thereby directly obtaining the tanδ value and capacitance.
Core anti-interference - frequency conversion technology: To solve the problem of power frequency (50Hz) interference in strong electromagnetic environments at substations and other sites, mainstream dielectric loss testers adopt the heterodyne measurement method. The instrument outputs a pure sinusoidal test signal at a non-power frequency (such as 45Hz/55Hz), fundamentally avoiding interference from the power frequency electric field, ensuring accurate and reliable test data even under strong interference.
