Improving Transformer Reliability with UV Technology
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Transformers are mission-critical assets in the power grid, responsible for adjusting voltage levels for efficient power transmission and distribution. These high-value components are built to last for decades, but any failure can have serious implications—from power outages to major financial losses. In recent years, the urgency to maintain transformer reliability has grown even more pressing due to extremely long lead times for new units, often exceeding a year. For utilities and manufacturers alike, preventing transformer failure has become a top operational priority.
A key contributor to transformer failure is partial discharge (PD), a localized electrical discharge that can occur under high voltage conditions. One of the most common forms of PD in transformers is corona discharge, especially on external components such as bushings.
UV imaging technology offers a powerful way to identify and pinpoint these partial discharges early and visually, allowing for smarter design, better manufacturing quality, and more proactive field maintenance.
Applying UV Technology in Transformer Design, Testing & Manufacturing.
In the early stages of transformer development, UV cameras are used during high-voltage design evaluations to uncover areas prone to corona PD activity. Components such as bushings and terminal connections are scanned during energization tests to reveal any points where the electric field causes discharges. This visual feedback enables engineers to modify component geometry or shielding early on, preventing future issues from emerging in the field.
UV imaging plays a particularly important role during high-potential (Hi-Pot) testing in manufacturing, where transformers are energized at 1.5 to 2 times their nominal voltage to verify insulation performance.
During these tests, UV cameras are used to scan external components—most critically the bushings, which are the primary interface between internal and external voltage systems. The detection of any corona activity during this process indicates the need for design refinement or corrective action, whether it’s a sharp edge, a contaminated surface, or an incorrectly installed connection.
By integrating UV inspection into factory acceptance testing, manufacturers ensure the transformer is free from PD sources before it leaves the plant. This improves QA processes, reduces rework, and delivers more robust equipment to the customer—essential in an industry where equipment replacement is costly and slow.
Preventing Failures in the Field – UV Inspections for In-Service Transformers.
Once transformers are installed and energized at substations, they operate under real-world stresses: environmental pollution, moisture, temperature variation, and aging insulation. In this setting, bushings remain one of the most vulnerable components. Corona discharges often develop on bushings due to surface contamination, weathering, or wear.
A particularly common source of discharge is the interface between the bushing and its metallic cap, where gaps, misalignment, or deterioration can allow electric fields to concentrate and trigger surface discharges. Without early detection, these localized events can lead to insulation breakdown or even catastrophic failure over time.
Utilities increasingly include UV imaging in their periodic inspection routines to detect corona discharges on transformers. A UV inspection allows maintenance teams to identify corona activity before it escalates into failure. These inspection results are especially valuable for planning targeted interventions—cleaning specific bushings, tightening connectors, or replacing degraded parts—without the guesswork or downtime of more invasive testing.
UV technology is also used after maintenance actions to verify that the issue has been fully resolved. For example, after cleaning a bushing, adjusting a connection, or reinstalling a corona ring, a follow-up UV scan can confirm that no discharge remains at rated voltage.
In highly polluted or coastal environments, utilities have even used UV inspections to optimize insulator washing cycles—prioritizing only the bushings and components with visible corona activity. This condition-based approach has saved some companies millions in unnecessary cleaning and reduced the risk of flashovers caused by postponed maintenance.
Conclusion
Once transformers are installed and energized at substations, they operate under real-world stresses: environmental pollution, moisture, temperature variation, and aging insulation. In this setting, bushings remain one of the most vulnerable components. Corona discharges often develop on bushings due to surface contamination, weathering, or wear.
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