| Company | America Utility Service |
| Location | USA |
| Timeline | 2018 |
| Project Overview | The Serveron TM8 DGA monitor detected a rapidly escalating thermal fault in a GSU transformer, enabling early intervention and preventing catastrophic failure. |
| Products | Qualitrol Serveron TM8 |
Preventing Transformer Catastrophe: How the Serveron TM8 Identified a Runaway Fault.
This is a Qualitrol Case Study. See the original article here
Background
In August 2016, a U.S. utility installed a Serveron TM8 dissolved gas analysis (DGA) monitor on a 3-phase, 1100 MVA, 345 kV Generator Step-Up (GSU) transformer. The transformer had been in service for less than two years, and during its early months of operation, it exhibited some gas generation, which was later traced back to a cooling system issue—one pump was running in reverse. After correcting the wiring, the issue seemed resolved, and gas levels remained stable for nearly two years.
Detection of a Critical Fault
On August 28, 2018, the Serveron TM8 detected an alarming rise in gas concentrations, specifically hydrogen, ethylene, and acetylene, signalling the potential onset of a severe thermal fault. The TM8’s “rate of change” alarm was triggered, alerting operators to the escalating issue. Over a span of just a few hours, gas concentrations increased dramatically, but not enough to activate the transformer’s Buchholz relay. With no immediate visible failure, the transformer was allowed to continue operating while monitoring continued.
By August 30, the transformer was taken offline for further inspection, as gas generation rates continued to rise even after the load was reduced.
Root Cause Analysis
A detailed internal inspection revealed localised burning of paper insulation and a severely damaged crimped connection between the LV cables and a bushing. The overheating was linked to high eddy losses, inadequate oil circulation, and an uneven current distribution. The analysis confirmed that the connection had been operating at extreme temperatures exceeding 300°C, causing thermal runaway and rapid gas generation.
Outcome and Lessons Learned
Thanks to the early warning provided by the Serveron TM8, operators were able to take proactive action before a catastrophic failure occurred. The faulty connection was repaired, and the transformer was successfully returned to service. Additionally, the detailed DGA data served as crucial evidence for the utility to secure warranty-covered repairs.
This case highlights the indispensable role of real-time online DGA monitoring in transformer asset management. By providing early and actionable insights, the Serveron TM8 enables utilities to prevent costly failures and extend transformer lifespan.