If a power transformer trips offline, which tests could be performed to ensure it is functioning properly?

The option that involves TTR (Transformer Turns Ratio), Megger insulation resistance testing, and power factor (PF) testing is particularly effective in evaluating the condition and functionality of a power transformer after it has tripped offline.

The TTR test measures the ratio of the primary to secondary voltage of the transformer windings. This helps in identifying potential issues such as shorted turns or open circuits within the windings. The accuracy of the turns ratio is crucial for ensuring that a transformer is operating as designed.

The Megger insulation resistance test assesses the integrity of the insulation materials within the transformer. Poor insulation can lead to malfunctions or ground faults, so this test helps confirm that insulation resistance is at safe levels, preventing electrical leaks.

The power factor test examines the transformer's dielectric losses and ensures that the insulation is not deteriorating. High dielectric losses can indicate insulation failure or other issues that may affect the transformer's performance.

Performing these tests collectively provides a comprehensive evaluation of the transformer's winding condition, insulation integrity, and operational efficiency, making it critical for confirming the proper functioning of the transformer after an offline trip.