What is the NETA Minimum DC Test Voltage for an Insulation-Resistance test on a 15kV dry-type transformer winding?

The NETA Minimum DC Test Voltage for an Insulation-Resistance test on a 15kV dry-type transformer winding is specified to ensure that the insulation integrity can be thoroughly assessed. In this context, a test voltage of 5000 volts is widely recognized as providing a sufficiently high level for evaluating the insulation of 15kV equipment without risking damage to the insulating materials.

This voltage level allows for an adequate breakdown of any moisture or contaminants that may be present in the insulation while remaining within safe limits for the transformer. Testing at this voltage is crucial, as it helps to reveal any potential weaknesses in the insulation system that could lead to faults or failures during the transformer’s operational life.

Using a lower test voltage may not yield a complete picture of the insulation's condition, as it might fail to stress the insulation to the degree needed to identify issues that could manifest under typical operating conditions. Thus, the choice of 5000 volts aligns with industry standards for ensuring reliability and safety in electric power systems.