Winding resistance testing is crucial for detecting potential faults in transformers by providing detailed insights into the condition of the internal windings, connections, and tap changers. Here’s how it helps identify specific issues:
Loose or Corroded Connections: High resistance readings can indicate loosened connections in the transformer windings or at terminals. Over time, as connections degrade or corrode, resistance increases, leading to localized heating, which can cause hot spots. This early indication allows maintenance to correct loose or poor connections before they become critical.
Winding Deformation and Mechanical Stress: Transformers experience significant mechanical stress, especially during short-circuit events or operational wear. Such stresses can deform windings, which can increase resistance. Testing after significant events or as part of routine maintenance helps detect shifts from baseline resistance values, suggesting deformation or physical displacement within the windings.
Thermal Deterioration of Insulation: Increased resistance is often accompanied by insulation wear, as overheating stresses the insulation material. While resistance testing alone doesn’t measure insulation condition, abnormal resistance could indicate overheating, prompting insulation assessment. This is especially useful in aged transformers where insulation degradation is more likely.
Inter-Turn Short Circuits: Inter-turn shorts occur when insulation between winding turns fails, creating low-resistance paths within the winding. Resistance testing can reveal subtle drops in measured resistance compared to baseline values, indicating a short circuit between winding turns that would otherwise remain hidden until a fault occurs.
Tap Changer Health and Contact Issues: Tap changers adjust transformer output by switching between winding taps, and resistance testing verifies their performance. Testing different tap positions helps check for consistent resistance values across the range, highlighting potential wear or poor contact in the tap mechanism. Irregular resistance values across taps may indicate issues like worn contacts or improper alignment.
Winding Continuity: High resistance values, or a complete open circuit reading, can signal winding discontinuity, suggesting breaks or severe faults within the winding. This type of testing is crucial following repair work or in-field incidents to confirm winding integrity.
Winding resistance testing provides early detection of internal issues, helping technicians monitor changes over time and preventing major faults or failures. Regular testing allows for trending analysis, comparing historical data to identify gradual deterioration, so maintenance can be scheduled before faults escalate into major transformer failures.
Nov 06,2024
