Analysis of Ozone Decomposition Rate for Evaluating Surface Partial Discharge Activities in Large-Scale Industrial Motors

This paper analyzes ozone decomposition coefficients and estimates the half-life time concerning insulation degradation diagnostics for large-scale industrial motors by monitoring ozone concentration. Partial discharges (PDs) that lead to the deterioration of insulation materials are significant on the surface of the semiconducting layer in the stator slots, and they appear at the coil ends. Simultaneously, the ozone generated by external PDs diffused into the motor frame. The amount of ozone generated per unit time represents the activity of the external PDs. The ozone generation and decomposition rates are equal at a steady state; therefore, the ozone generation rate is obtained from the ozone decomposition rate. However, the ozone decomposition coefficient due to collisions with water vapor has not yet been determined. The ozone decomposition rate due to collisions with the chamber vessels must be determined individually. Ozone decomposition rates are investigated based on the background described above. This study presents the ozone decomposition rates due to collisions with water vapor and the chamber vessel, analyzed from data in literature. The humidity effect coefficient obtained is approximately 2.75× 10-23s-1cm3/ particle. The wall effect depends on the configuration and material of the chamber vessel. The halflife time is estimated using the analyzed coefficients and correlates well with the measured data.