What is a common initial step before beginning the testing of transformers?

Visual inspection is a standard initial step before testing transformers because it allows technicians to identify any obvious physical issues or signs of deterioration that could impact the performance and safety of the transformer. During this inspection, technicians will examine the physical condition of the transformer, checking for signs of oil leaks, corrosion, loose connections, or any other visible faults. This step is crucial as it helps to ensure that the transformer is in suitable condition for testing and can also help avert potential hazards or damage to the test equipment.

Replacing all the transformers, checking power levels, or calibrating the testing equipment are actions that may follow a visual inspection. However, they are not the first action taken, as it's essential to assess the physical state of the equipment before proceeding with more technical evaluations or interventions. This systematic approach ensures that all potential issues are addressed early in the testing process.