Sampling of transformer oil is an important stage in the diagnosis of the current state of oil-filled equipment. To date, there are techniques that allow you to conclude on the basis of the analysis of the samples taken that repairs are necessary.
For sampling from electrical apparatus of open substations, it is necessary to choose dry weather. This operation is carried out by a team of two people. One of them is the manufacturer of works with the electrical safety group at least 4th, and the other is a member of the brigade with the electrical safety group no lower than the 2nd.
For the sampling of transformer oil filtration, glassware of transparent glass with a capacity of 0.5-1 liters is used. Preliminary it must be prepared and dried in a special drying cabinet. Its specificity is also the delivery of such dishes first to the place of sampling, and then to the place of testing. It is carried out in special wooden boxes with cells of appropriate dimensions. Use of dishes for sampling for any other purposes is not allowed.
Sampling of oil samples is carried out during normal operation of electrical apparatus or immediately after their shutdown. The fulfillment of these conditions is necessary in determining the amount of moisture, as well as other characteristics, depending on its presence in the oil. At the same time, the ambient air temperature is fixed, as well as the sampling time.
Transformer oil filtration
In general, the oil sample should be taken from the bottom of the oil-filled equipment. To do this, you must perform the following actions:
– wipe the oil sump;
– drain the oil to flush the tap hole;
– drain 2-10 liters of dirty oil and condensate, excluding its contact with the ground;
– flush the sampling bowl twice with oil;
– fill the dishes with 95-98% by volume without the formation of air bubbles and the presence of undissolved precipitated water;
– tightly close the dishes with a cork, previously washed with the same oil. In this case, any contact of the sample with air should be avoided.
After sampling, a special label with the date, substation name, transformer parameters or other electrical apparatus, from which the sample was taken, its voltage, the reason for sampling, the name of the sampling sample, is hung on the selected dishes.
Delivery of samples to the laboratory should be carried out not later than 7 days from the moment of their selection. If the storage is longer, samples can be changed, which can lead to a discrepancy between the results obtained and the oil condition in the electrical apparatus.