Dynamic Polarization Depolarization Losses under Non Equilibrium Radial Heat Diffusion Conditions
Dynamic radial thermal gradients shift peak electric field stress outward and double dielectric depolarization losses compared to isothermal estimates.
Space Charge Trapping
Meaning
Localization of electrical charge carriers in deep potential energy wells within the molecular structure of an insulating polymer. When space charge trapping occurs, it creates a localized electrical field that can exceed the design limit of the insulation. This accumulation of trapped charge is a major cause of premature dielectric aging and failure in high-voltage cables.
Charge Accumulation
The physical mechanism of trapping involves defects, impurities, and chemical by-products of the cross-linking process. When electrons or holes are injected from the electrodes, they become immobilized in these localized states rather than flowing through the polymer. Over time, the accumulated charge modifies the internal potential distribution of the cable insulation.
Diagnostic Testing
Pulsed electroacoustic measurements are used to map the spatial distribution of these trapped charges in the dielectric material. These tests are conducted on prototype cables subjected to long-term high-voltage stress to determine the charge retention behavior. The results help to optimize the chemical formulation and the degassing time used during manufacturing.
Development Risk
Failing to control the density of charge traps can lead to early failure during the rigorous cable qualification trials. If the demonstration batch has not been sufficiently degassed to remove the polar by-products, the trapped charges will cause catastrophic breakdown during polarity reversal tests. Ensuring a low level of space charge trapping is therefore a critical step in the transition from pilot formulation to continuous industrial extrusion, saving the manufacturer from the massive financial losses of rejected production runs.