Use the standard's "reactance deviation" method for condition monitoring. A sudden 3–5% change in measured reactance (compared to factory acceptance tests) is an early indicator of winding movement or core damage—before a DGA (dissolved gas analysis) shows fault gases.
IEC 60076-6 provides specific guidance on the measurement and tolerance of losses. Since reactors are inductive loads, "efficiency" in the traditional transformer sense is not applicable. Instead, the focus is on minimizing losses (no-load loss equivalent) to reduce operational costs for utilities. The standard defines reference temperatures for loss measurement, ensuring consistency across different manufacturers. iec 60076-6