Condition monitoring (CM) of electrical equipment is a key element to reduce the cost of unscheduled maintenance and improve effectiveness, performance and reliability of the equipment. The condition and performance can be monitored through analyzing the temperature, vibration or radio frequency (RF) emission of the equipment, which can give an indication when faults are developing. In the past decades, intensive research works have been conducted to study the CM, and thus, the state-of-art in this field is felt important to be reviewed. In this paper, we review some of the popular approaches in the field of CM using three parameters namely; temperature, vibration, and RF emission. A brief overview on each existing monitoring methods is presented and from the comparison between the existing methods, it is concluded that with proper analysis and reliable measurements, RF emission can present an excellent tool for monitoring electrical equipment. It is believed that this review would give the readers a good insight on various schemes and approaches of CM of electrical equipment.