Power Transformer Testing & Issue Detection With Omicron Equipment

Project Scope

Our team was tasked with performing advanced diagnostic testing on the 25MVA transformer using the latest Omicron equipment, specifically the Testrano 600 and the Omicron FRAnalyzer (FRA) for Sweep Frequency Response Analysis (SFRA), to ensure a thorough evaluation of both electrical and mechanical integrity. The tests included:

• Winding Resistance Measurement: To detect possible winding degradation and connection issues.
• Dynamic Resistance Measurement: To evaluate tap changer condition under real-time load.
• Sweep Frequency Response Analysis (SFRA): Using the Omicron FRAnalyzer to identify any potential winding displacement, core issues, or mechanical deformation.
• Power Factor/Tan Delta Testing: To assess the insulation condition and detect moisture or contamination.

Testing Process

Upon initial inspection, our engineers conducted a series of baseline tests to assess the general health of the transformer. Utilizing the Testrano 600, we measured winding resistance and dynamic resistance values across all tap positions. This allowed us to analyze the stability of the tap changer and identify any resistive imbalances. The Omicron FRAnalyzer was then employed for detailed SFRA testing, providing critical insight into the state of the transformer’s core and winding structure.

Discovery of a Potential Asset-Destroying Issue

During the SFRA test, our engineers noticed a significant anomaly indicating possible core displacement. Further investigation with the FRAnalyzer revealed an unusual deviation in the frequency response, suggesting a loose core connection – a condition that, if left unchecked, could lead to excessive vibration, mechanical fatigue, and ultimately catastrophic failure of the transformer.

In addition, the dynamic resistance measurement revealed erratic readings on the tap changer, pointing to potential wear and tear that could cause severe operational issues under load. Our findings highlighted a probable asset-destroying issue, which could have led to costly unplanned outages for the client.

Recommendations

Based on our analysis, Johnson & Phillips recommended immediate remedial action to prevent further deterioration and extend the asset’s operational life:

1. Core Re-Clamping: Engage in core tightening procedures to secure the connections and mitigate vibration issues.
2. Tap Changer Overhaul: Schedule a maintenance overhaul to inspect and replace worn tap changer components.
3. Enhanced Monitoring: Implement continuous online monitoring for early detection of future issues, reducing the likelihood of unexpected failures.