According to NETA acceptance testing standards, when should a transformer manufacturer be consulted regarding winding-resistance test values?

In the context of NETA acceptance testing standards, consulting with the transformer manufacturer regarding winding-resistance test values is crucial when there is a variation of more than 2 percent. This threshold is established to ensure that any significant discrepancies in winding resistance are addressed, as these variations can indicate potential issues such as poor connections, damage to the windings, or other integrity concerns within the transformer. Consulting the manufacturer helps to assess whether the observed values are within acceptable limits based on design specifications and operational expectations. This proactive approach not only aligns with standard testing protocols but also helps maintain equipment reliability and performance.