Methods to reduce errors for DC electric field measurement in oil-pressboard insulation based on Kerr-effect

TLDR: In this paper, a Kerr-effect based noncontact and real-time electric field measurement system was proposed to measure the electric field in liquid dielectric insulating materials, where the measurement errors resulted from the edge effect generated by electrode and pressboard.

Abstract: Kerr-effect based methods show great potential for the measurement of electric field in liquid dielectric. However, the accuracy of the Kerr-effect based measurement over the DC electric field in oil-pressboard insulation remains to be a challenge. With the establishment of a Kerr-effect based non-contact and real-time electric field measurement system, the present paper analyzes the factors causing the measurement errors and thus proposes the countermeasures accordingly. It is indicated that the measurement errors resulted from the edge effect generated by electrode and pressboard could be reduced to 1.3% by lengthening the electrode, shortening the spacing distance between the electrode and the test chamber, and providing the electrode covering. The errors caused by non-ideal characteristics of the optical devices could be adjusted through the calibration of its parameters. The errors caused by the noise from laser source could be reduced to 0.86% for DC electric field and 1.6% for AC electric field through suitable selection of AC modulation frequency as 1310 Hz, which could also improve the signal-to-noise ratio. The test results conclude that the measurement system established under the present research could accurately measure DC electric field of 20 V/mm with the error being smaller than 5.4%.