SFRA Test Sets play a vital role in power systems. They are key detection and diagnostic tools for ensuring the safe, reliable, and economical operation of transformers. Their main applications are manifested in the following aspects:
1.Fault Diagnosis and Localization:
Post-Fault Assessment (Short-Circuit Events): After a transformer experiences an external or internal short-circuit current surge, the massive electromagnetic forces can cause mechanical deformation of the windings, such as displacement, twisting, bulging, or collapse. The winding deformation tester can quickly and non-destructively detect such deformations and their severity, helping to determine whether the transformer can continue operating or requires repair/replacement.
Locating Fault Points: By analyzing the deformation curves (especially comparing phases or comparing against historical data), the approximate location (e.g., HV, LV, tap changer winding) and region (axial, radial) of the deformation can be identified, guiding subsequent repairs.
2.Preventive Testing and Condition Assessment: Incorporating winding deformation testing into the transformer's routine preventive testing plan:
Establishing a Baseline Fingerprint: Test new transformers before commissioning, after major overhauls, or when confirmed to be in good condition to establish an original, healthy "fingerprint" spectrum (frequency response curve).
Periodic/Event-Driven Retesting: Retest periodically (e.g., aligned with dissolved gas analysis cycles) or after special events that may cause winding stress (e.g., nearby short circuits, transportation, strong earthquakes, abnormal vibrations, overload operation).
Condition Comparison: Compare retest results with the original fingerprint or historical data to determine if the winding structure has changed. It can sensitively detect even minor changes, providing early warning of deformation in its initial stages, before it develops into a serious fault (such as insulation breakdown), enabling predictive maintenance.
3.New Transformer Acceptance and Commissioning Tests:
Verifying Manufacturing Quality: Conduct winding deformation tests during factory acceptance tests and on-site commissioning tests after installation to verify if the windings sustained any damage or deformation during manufacturing, transportation, or installation, ensuring the equipment is in good initial condition.
Providing Baseline Data: Supply baseline data on the initial state for subsequent operation and maintenance.
4.Post-Overhaul and Post-Transportation Inspection:
Post-Overhaul Verification: After a major tanking removal overhaul (involving winding inspection, tightening, spacer block replacement, etc.), perform testing to verify that the winding structure was correctly restored and undamaged during the repair process.
Post-Transportation Assessment: Transformers can suffer from internal structure loosening or deformation (especially windings) due to vibration and impacts during long-distance transportation. Winding deformation testing upon arrival and positioning is a crucial acceptance step.
5.Short-Circuit Withstand Capability Assessment and Verification:
By comparing winding deformation test results before and after a transformer endures a short-circuit current surge, the actual severity of the short-circuit impact on the transformer and its true short-circuit withstand capability can be quantitatively assessed. This provides evidence for equipment rating and safe operation.
6.Accident Cause Analysis:
After an internal transformer fault (especially turn-to-turn shorts, winding-to-ground faults) causes damage, performing a deformation test on any non-completely destroyed windings (sometimes combined with tanking removal inspection) helps analyze the cause of the accident, determining whether it stemmed from initial winding deformation or if electromagnetic forces from the short-circuit were the direct cause.