Reading a VIE Health Report: A Walk-Through for New Users
The health report is where the data becomes a decision. VIE's platform collects continuous vibration, thermal, and oil measurements from each transformer and organizes them into a structured report that tells you three things for every metric: what the current value is, whether it is trending, and what the trend means for the asset.
Reading the report correctly is a skill. It takes a few cycles to build. This article walks through the structure, the logic behind each section, and two examples of what the report looked like when it caught something real.
The Structure of a Health Report
A VIE health report is organized by metric category, moving from the indicators most likely to give early warning to those that confirm what is happening right now. That sequence reflects the diagnostic chain: leading indicators at the top, coincident indicators below.
Each metric appears with its current value, a trend line showing its behavior over the monitoring period, and a status designation: stable, watch, or flagged. Stable means the metric is within its normal range and not trending toward a threshold. Watch means the value is moving in a direction that warrants attention at the next scheduled review. Flagged means the metric has crossed a threshold and a specific response is recommended.
The report also shows operating conditions at the time of each reading: load, voltage, and ambient temperature. Those three variables are what the analytics engine uses to separate a signature change caused by operating conditions from one caused by the asset itself.
When Leading Indicators Flag
Leading indicator flags are directional signals. They tell you something is shifting. They do not tell you the transformer is about to fail. The appropriate response is a targeted confirmatory test, not an emergency shutdown.
Rising WHr (Radial Winding Health Metric): Order a MEGGER test or insulation resistance measurement. If WHr has been rising steadily over multiple reporting periods, the winding is experiencing increasing radial mechanical stress. The MEGGER test will tell you whether insulation quality is degrading in parallel.
Rising WHa (Axial Winding Health Metric): Same confirmatory path as WHr. If both WHr and WHa are flagged simultaneously, escalate the response. Order Sweep Frequency Response Analysis (SFRA) to assess whether mechanical displacement has already occurred. Correlate with any available Dissolved Gas Analysis (DGA) history. Consider accelerating the inspection timeline rather than waiting for the next scheduled review.
Rising Oil Health Metrics (V2P or S2P): Order an oil quality lab test. The panel should cover moisture content, interfacial tension, dielectric strength, acid number, power factor, and total dissolved combustible gas. For any unit over 20 years old, or one with prior thermal events in its history, add furan analysis.
Partial Discharge flag: Run a correlating DGA immediately. PD that appears alongside rising thermal metrics may indicate arcing or sparking rather than simple void discharge. The distinction changes the urgency of the response.
In all cases, the leading indicator flag is the beginning of a diagnostic sequence, not the end of one. The flag points you toward the right test. The test provides the confirmation.
When Coincident Indicators Flag
Coincident indicator flags require a faster response than leading indicator flags. They describe what is happening now, not what is developing.
Elevated or rising Impact Metric (NHv, NHa): Validate immediately with available DGA trends and any recent electrical test results. An elevated Impact Metric means the transformer structure is under significant mechanical stress at this moment. If DGA trends and electrical test results are also moving negatively at the same time, treat the combined picture as a priority event.
Excess Heat Flux (Thermal Metrics): The location of the thermal anomaly matters as much as its magnitude. Elevated heat flux concentrated at the top of the tank points toward insulation stress or load-related overheating. Elevated heat flux at lower sensor heights points toward a cooling obstruction. The two scenarios call for different responses: DGA correlation for the former, cooling system inspection for the latter. If both thermal metrics and oil health metrics are rising together, treat the combination as a priority flag regardless of where in the tank the thermal anomaly appears.
The Convergence Principle
The single most important concept for reading a VIE health report is this: risk is highest when VIE metrics and independent oil or electrical test results trend in the same direction at the same time.
A rising WHr on its own is a signal to schedule a MEGGER test. A rising WHr combined with a MEGGER result showing degraded insulation resistance on the same unit is a different situation entirely. The two data streams are independent. They are measuring different physical properties through different methods. When they agree, the probability that something real is developing is substantially higher than when only one is flagged.
The same logic applies across every metric pair: rising oil health metrics confirmed by a lab test showing elevated dissolved gas, elevated Impact Metric confirmed by a DGA result with a RETEST IMMEDIATELY designation, thermal anomaly confirmed by oil lab results showing active degradation. In each case, the convergence of VIE's continuous signal and an independent confirmatory test is the clearest indication that action cannot wait.
What This Looks Like in Practice
The following two cases are drawn from VIE deployments. Customer and site details are anonymized.
Case I: Medium-Stage Winding Deformation
A large power transformer at a transmission substation operated by a North American utility showed a gradual, sustained rise in its Radial Winding Health Metric over a period of several weeks. The trend was consistent across multiple reporting periods and not explained by changes in load or voltage. Oil health metrics and thermal metrics were stable.
VIE's recommended action was a targeted MEGGER test. The test returned a degraded insulation resistance reading on the flagged unit. A healthy unit of comparable age and rating at the same facility returned a significantly better result under the same test conditions. The comparison confirmed that the WHr trend was reflecting a real mechanical change in the winding, not a measurement artifact.
The transformer was scheduled for inspection. The inspection confirmed medium-stage winding deformation. The unit was taken out of service and repaired before it reached a failure condition.
Case II: Deformed Winding With Thermal Anomaly
A second transformer at a different facility showed concurrent elevation of the Radial Winding Health Metric and an emerging thermal anomaly in the upper tank region. The two flags appeared within the same reporting period.
Per the convergence principle, the combination was treated as a priority rather than a watch item. A MEGGER test confirmed degraded insulation resistance. An oil lab report returned elevated Ethane levels with a RETEST IMMEDIATELY designation, indicating active thermal degradation of the insulating oil.
The asset was taken out of service for emergency inspection. Winding deformation was confirmed alongside evidence of thermal stress in the insulation system. The timeline between the first VIE flag and the emergency inspection was short enough that the transformer was recovered rather than replaced.
Both cases illustrate the same sequence: VIE provides direction, confirmatory testing provides validation, and the combination of the two produces a decision with enough lead time to act on it.