The maintenance of electrical power transformers in sub-stations is critical to power distribution in the United States.   These transformers are filled with oil for the purpose of cooling the transformer.   Inside these units are one or more coils of wire wound around each other.   Paper insulation is placed between the coils so that the wires of each coil do not touch the wires of another coil.  This is needed to prevent a short circuit.  Water or moisture in the oil will migrate to the paper and over time breakdown the electrical insulation value of the paper.  This causes a degradation of the efficiency of the transformer and can lead to an explosion. 

Standard Solutions to the Problem: Most power companies monitor the moisture condition of transformers by periodically taking a sample of the oil. The oil samples are taken to a laboratory (both outside testing labs as well as power company operated labs). The moisture test results are obtained by using a Karl Fisher Titrator.  The data is then logged.