Thompson-Lampard Theorem for Dielectric Characteristics Detection of Generator Stator Insulation

Abstract

Abstract The insulation of large generator stator winding will be gradually aging in the long-term operation process. The traditional aging test method cannot accurately locate the non-penetrating local defects of winding. Interdigital electrode is widely used in the fields of environmental monitoring and food detection because of its excellent characteristics such as self-closing and unidirectional penetration, but it has not been popularized in the identification of generator insulation aging. The paper proposes an interdigital electrode structure based on the Thompson-Lampard theory. The electrode suitable for dielectric characteristic detection of stator winding, and the electrode structure is optimized by using the finite element method from the parameters of signal strength, sensitivity and penetration depth. With the help of optimising, the measuring accuracy of the electrode can reach 0.1 level. Then, the different moisture conditions of water-cooled generator and air-cooled generator are simulated to verify the feasibility that interdigital electrode can detect insulation moisture which is an important factor in accelerating insulation aging. Finally, the moisture depth detection results show that the electrode combination based on the Thompson-Lampard theory can be used to locate moisture depth accurately, it is of great significance for the prevention of insulation aging and the pre-diagnosis.