Apparatus and methods for use in determining the presence of materials entrained within a medium

A power generation system comprising:

• a machine comprising at least one transformer including a medium contained therein;
• a sensor assembly positioned proximate to said at least one transformer, said sensor assembly comprising:
• at least one probe comprising a microwave emitter, said microwave emitter is configured to generate at least one electromagnetic field from at least one microwave signal;
• and
• at least one signal processing device coupled to said at least one probe, wherein said at least one signal processing device is configured to detect a change in the dielectric constant of the medium at a frequency received from said microwave emitter and to compare an expected power level of the frequency received from said microwave emitter with an actual power level of the frequency in order to determine a presence of at least one material entrained within the medium.