Dynamic temperature monitoringand life assessment techniques for electrical machines

Presently the focus of utility is to not only carryout cost reduction measures but also ensure high reliability standards of the entire system. The new concept of overall system design life analysis and implementation of diagnostic tools can enhance the equipment availability by increased maintenance intervals. It is not always desirable to consider the very high design margins, rather should be based on provisions of latest international standards, insulation aging process and the average ambient conditions of the site. The past design practices and concept needs a review in light of new developments and standards introduced in recent past. The need of hour is to develop design tools based on new concepts and adopt in the system. Here a few insulation aging concepts and testing methods have been described used to ensure adequacy of machine insulation system for the desired application and equipment life. It has also been suggested to measure the ‘temperature rise’ instead of ‘absolute temperature, for electrical machines. The paper describes the conventional concept of insulation monitoring and than discuss the superiority of the new dynamic monitoring concept. The life assessment test methods for electrical machines, thermal endurance relationship, operating voltage versus insulation life, load versus temperature rise relationship have been deliberated in the article. The concept of insulation aging and its correlation with the permissible temperature rise limits has been worked out.

The latest diagnostic techniques enable us to move away from conservative schedule OEM systems, and opt for ‘Right maintenance at the right time’. The present system of supervision of the equipments, based on absolute insulation temperature needs to be reviewed at this stage, for major critical equipments. The demand of utilities is towards having a system, which senses the fault right at the incipient stage. The customer need for high quality, reliability, optimal cost, desired margins along with self-supervision & monitoring system has to be ensured.