IEEE C57.12.200-2022 PDF
This document provides guidelines for performing a bushing dielectric frequency response (DFR) measurement either in the field or in the factory. The measurement technique, measuring equipment requirement, and interpretation of results based on comparison are included in the normative text. Additional theories related to DFR such as temperature correction using the Arrhenius equation, influence of voltage, and a few case studies are described in the annexes.
The purpose of this guide is to provide a diagnostic tool for bushing condition evaluation in the field to reduce unexpected transformer failures and unplanned outages. Bushing manufacturers performing the DFR measurement on a bushing during the factory acceptance or transformer commissioning test could act as a baseline signature that is compared with the results obtained later. Given the same test conditions, the trending of the insulation condition can be observed through comparison. This process gives the test engineers an additional way to identify defects in the bushing insulation system at an early stage.
New IEEE Standard – Active. Bushings are critical components for power apparatus as their main role is to conduct current at high voltage through a grounded barrier. Statistical studies have shown that bushing defects such as water ingression and partial discharge are among the most important causes for unexpected failures. Dielectric frequency response (DFR), sometimes also known as frequency domain spectroscopy (FDS), which involves measurement of the bushing capacitance and dielectric losses over a frequency range, is an effective method to detect deterioration of bushing insulation. This guide applies to the DFR measurement of various types of bushings either in the field or in the factory except for gas-insulated bushings.
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