| Company | American Utility Service |
| Location | USA |
| Timeline | 2018 |
| Project Overview | This case underscores the importance of continuous online monitoring in preventing catastrophic failures |
| Products | Qualitrol Serveron TM8 |
This is a Qualitrol Case Study.
Background
In 2016, a United States utility installed a Qualitrol Serveron TM8 transformer monitor on a transmission transformer to provide continuous online diagnostics and condition monitoring. The asset operated reliably for several years without incident. However, on 19 December 2018, the TM8 system triggered alarms indicating a significant rise in acetylene levels within the transformer oil. Acetylene is a key indicator of high-energy internal faults, particularly hot metal activity. This alert followed earlier detections of increased ethylene, methane, and hydrogen concentrations, which already suggested developing thermal stress and overheating within the unit.
Critical Detection and Response
Following the initial alarm, the TM8 automatically increased its sampling frequency, enabling higher-resolution gas analysis. This escalation provided near real-time insight into rapidly changing conditions inside the transformer. Within a 24-hour period, the data confirmed a sharp increase in fault gases associated with hot metal activity, indicating an accelerating internal issue. Armed with this detailed information, the utility was able to respond quickly and decisively. On 20 December 2018, just 28 hours after the first warning, the transformer was safely removed from service to prevent further deterioration or catastrophic failure.
Root Cause Analysis
A detailed post-event inspection identified the root cause as a loose nut located on the PA core leg of Phase 1. The investigation found that thread damage on the nut, likely caused by insufficient torque applied during the original manufacturing process, had allowed it to gradually loosen over time due to normal operational vibration. This mechanical failure led to localised overheating, which in turn generated the dissolved gases detected by the monitoring system. The affected PA unit was subsequently replaced following a full inspection and remediation process.
Conclusion
This case highlights the critical value of continuous online transformer monitoring in modern power systems. The Serveron TM8 not only provided early detection of a developing internal fault, but also delivered high-resolution diagnostic data that enabled informed decision-making. As a result, the utility was able to intervene before catastrophic failure occurred, significantly reducing potential damage, minimising outage duration, and avoiding costly repairs.