HEAT RUN TEST (COOLING TEST)
In order to ensure the normal continuous trouble-free operation of power transformers, it is important to monitor and comply with the acceptable limits of various parameters. One of them is a temperature conditions.
Specially designed cooling systems help to follow the temperature conditions, that are set for each type of transformer. However, regardless of the type of system, its operation also should be controlled by non-demountable methods. In advance it is worth pointing that it doesn't extend to an emergency situation. For such situations there is a special diagnostic mode - «heat run test» or cooling test.
The modern milli-ohmmeter MIKO-9A is equipped with this additional mode, that consider the main purpose of measuring electrical resistance.
The test procedure and the rules for processing the results meet the requirements of paragraph 2 in all-Union State Standard 3484.2-88 ("Power transformers. Heat run test"). The standard consider that the DC resistance measurement of the transformer winding during the cooling process is carried out without pauses and the results are periodically saved in the memory of the instrument (converted to temperature values).
The temperature of winding-time relationship is counted since the moment of the imeasurement start-up, and can be represented in a tabular or graphical form.