  Transformers are critical assets in power systems and transformer failures
can cause asset damage, customer outages, and safety concerns. Dominion Energy
has a sophisticated monitoring process for the transformers. One of the most
cost-efficient, convenient and practical transformer monitoring methods in
industry is Dissolved Gas Analysis(DGA). Leveraging new technology, on-line
transformer monitoring equipment is able to measure samples automatically. The
challenges of unstable sampling measurements and contradicted analysis results
for DGA are discussed in this paper. To provide further insight of transformer
health and support a new transformer monitoring process in Dominion Energy, a
DGA monitoring system is proposed. The DGA analysis methods used in the
monitoring system are selected based on laboratory verification results from
Dominion Energy. After derive the thresholds from IEEE standard, the solution
of the proposed monitoring system and test results are presented. In the end, a
historical transformer failure case in Dominion was analyzed and the results
indicate the monitoring system can provide prescient information and sufficient
supplemental report for making operational decisions.
