On which type of day should oil samples ideally be taken?

Taking oil samples on a dry day is ideal because it minimizes the risk of moisture contamination in the samples. When oil is collected in a humid or wet environment, the likelihood of water being introduced into the sample increases, which can lead to inaccurate test results and potential misinterpretations of the oil's condition and performance. This is particularly important for oils used in transformers and other equipment, where moisture can significantly affect the insulation properties and overall performance.

Selecting a dry day ensures that the samples reflect the true condition of the oil without the interference of added moisture, allowing for more reliable and effective maintenance decisions. In contrast, taking samples on wet days or in humid conditions could result in faulty analyses, compromising the reliability of maintenance strategies. Therefore, sampling on a dry day is a best practice in substation maintenance.