When VIE Flags a Problem: What to Do Next
Important: The guidance in this article is diagnostic in nature. VIE identifies leading and coincident indicators of transformer health and recommends confirmatory tests based on those indicators. VIE does not direct operational decisions. All maintenance actions, inspection schedules, and equipment decisions are the sole responsibility of the asset owner and their qualified personnel. VIE Technologies is not liable for outcomes resulting from actions taken or not taken in response to this guidance.
A rising metric in VIE does not mean a transformer is failing. It means something has shifted, and the shift points toward a specific type of investigation. The alert tells you where to look. The confirmatory test tells you what you are looking at.
Every metric flag has a logical next step. The steps below are organized by flag type, from leading indicators to coincident indicators, ending with the principle that governs how to prioritize when more than one metric is flagged at once.
If WHr or WHa Is Rising
A rising Radial Winding Health Metric (WHr) or Axial Winding Health Metric (WHa) indicates mechanical stress on the winding or core structure. The recommended first response is a targeted insulation resistance measurement or MEGGER test.
The MEGGER test will tell you whether insulation quality is degrading alongside the mechanical change. VIE's winding health metrics show strong correlation with insulation resistance across modern transformers — a rising WHr that coincides with a deteriorating MEGGER result is a significantly stronger signal than either reading alone independently.
If WHr and WHa are both elevated at the same time, 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 from the most recent annual lab test. Consider accelerating the inspection timeline rather than waiting for the next scheduled review cycle.
If Oil Health Metrics Are Rising
Rising V2P or S2P values indicate oil quality is deteriorating. The recommended response is an oil quality lab test.
The test panel should cover moisture content, interfacial tension, dielectric strength, acid number, power factor, and total dissolved combustible gas (TDCG). For any unit over 20 years old, or one with prior thermal events in its service history, add furan analysis to assess the condition of the paper insulation.
The rate and character of the rise in VIE's oil metrics can guide the urgency of the response. A slow, sustained climb over several weeks suggests gradual degradation. Schedule the oil test within 30 days. A sharper or more abrupt change warrants an expedited test, particularly if the unit is older or has a history of thermal stress.
If Partial Discharge Is Detected
A partial discharge flag in VIE calls for a correlating DGA immediately. Do not wait for the next scheduled annual test.
PD activity that appears alongside rising thermal metrics is a more urgent finding than PD detected in isolation. The combination may indicate arcing or active sparking rather than localized void discharge, and the urgency of the response changes accordingly. If the DGA result returns elevated acetylene or hydrogen alongside a rising thermal anomaly, treat the combined picture as a priority event.
VIE detects a significant proportion of PD activity, but not all of it. Full PD localization, when needed, requires dedicated acoustic or electrical PD testing methods. A DGA correlation is the right first step. PD localization follows if the DGA confirms active discharge.
If the Impact Metric Is Elevated
An elevated or rising Impact Metric (NHv or NHa) is a coincident indicator. It does not describe what is coming. It describes what is happening now.
Validate immediately with available DGA trends and any recent electrical test results. An isolated spike in the Impact Metric may reflect an external network event (a nearby fault, a through-fault, or physical shock during nearby work) rather than a developing internal problem. Trend and context matter. A sustained elevation, or one that coincides with network events known to stress the transformer, is a stronger diagnostic signal.
If DGA trends and electrical test results are also moving negatively at the same time as an elevated Impact Metric, treat the situation as a priority event. The convergence of multiple independent signals pointing in the same direction is the clearest indication that action cannot wait.
If Thermal Metrics Are Rising
The appropriate response to a rising thermal metric depends on where in the tank the anomaly is appearing.
Excess heat flux concentrated at the top of the tank points toward thermal stress in the upper winding region: overloading, insulation degradation, or oil quality issues affecting heat dissipation. Increase VIE monitoring frequency and correlate with recent DGA trends. If DGA shows rising dissolved combustible gas alongside the thermal anomaly, escalate.
Excess heat flux at lower sensor heights, or a profile that does not follow the expected top-weighted thermal gradient, points toward a cooling obstruction. Check for blocked radiator fins, sludged or contaminated oil reducing circulation, or a failed cooling pump or fan. Address the cooling issue first. In many cases, restoring adequate cooling prevents further thermal damage and removes the metric from alert status without requiring additional electrical testing.
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: When Multiple Metrics Flag Together
Risk is highest when VIE metrics and independent oil or electrical test results trend in the same direction at the same time.
A single rising metric calls for a targeted confirmatory test. Two metrics trending together call for an accelerated response. A VIE flag confirmed by a laboratory or electrical test result pointing in the same direction is not a coincidence. It is the diagnostic chain working as it should, and it demands action.
The clearest high-risk signals are:
- Rising WHr or WHa confirmed by a deteriorating MEGGER result on the same unit
- Rising oil health metrics confirmed by a lab test showing elevated TDCG or a RETEST IMMEDIATELY designation
- An elevated Impact Metric confirmed by rising DGA trends in concurrent test results
- A 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 point at which deferral stops being reasonable. Schedule the inspection. Do not wait for the next scheduled review.
For more on how to read a VIE health report and interpret the full metric picture, see [Reading a VIE Health Report: A Walk-Through for New Users].