Improving existing motor protection for medium voltage motors

Motor failures and associated present-day costs are analyzed, and potential troubles generated within the plant and form the utility distribution system are documented. These troubles, their effects, and resultant motor failure modes are illustrated to determine the maximum protection desired for prolonged motor life. Limitations of older forms of motor protection utilizing induction-type overcurrent relays are presented in contrast with the desired protection. The features of several different types of current microprocessor-based relays are reviewed as eligible candidates for motor protection upgrading. An example of work performed as part of a comprehensive field retrofit is presented along with economic considerations