Natural esters and online DGA

In recent years, there has been a notable increase in the utilization of natural esters as liquid insulation in transformers. This trend is primarily driven by their superior fire safety and biodegradability compared to traditional mineral oils. While natural esters were previously confined to smaller transformers, particularly in distribution networks, their application is expanding to larger transformers, including the retrofilling of older mineral oil-filled ones.

Monitoring natural ester-filled transformers

The growing prevalence of distributed electric power generation and the dynamic loading of aging infrastructure underscore the importance of continuous monitoring for transformers. Online dissolved gas analysis (DGA) emerges as a practical tool for assessing the transformer condition and detecting various faults at an early stage.

However, interpreting DGA data for natural esters differs somewhat from mineral oils due to variations in gas ratios stemming from differences in chemical composition. Organizations like CIGRE are actively engaged in accumulating more DGA information on the existing population of ester-filled transformers to enhance guidance for DGA of esters.

Solving the challenges – enter the OPT100

Despite their advantages, natural ester liquids pose a challenge due to their susceptibility to oxidation and polymerization in the presence of oxygen. Consequently, transformer tanks must be hermetically sealed against air, the source of oxygen.

Vaisala OPT100 online DGA monitor addresses this challenge with two specific features beneficial for monitoring ester-filled transformers. In addition to the seven key gases used in fault diagnostics, it measures total gas pressure (TGP), offering a direct and real-time indication of any air leakage in the transformer.

Moreover, its fully hermetic measurement cycle prevents the liquid or gases from coming into contact with air at any point, preventing ester polymerization within the monitor itself