Condition Assessment of Rotating Machine Insulation: Case Studies from Power Plants

Abstract

Unexpected failure of rotating machines in the power plant can cause unnecessary expense. Thus, appropriate preventive and predictive maintenance should be planned and scheduled, to avoid premature failure of the machines and to ensure the reliability and safe operation of the systems. Besides, the online monitoring technique has an advantage as it can monitor the condition periodically without interrupting the equipment and it can measure even during actual operating conditions while off-line tests can't. Indeed, the most vulnerable part of the equipment is the insulation since it is subjected to several stresses during service which can alter the insulation condition, so-called degradation. Hence, this paper intends to present the experience of insulation condition assessment on generators and motors in power plants in Thailand. Several test techniques were conducted on the machines during the annual outage including the polarization and depolarization current (PDC) analysis, off-line partial discharge (PD) test as well as dissipation factor and capacitance tip-up. Those diagnostic test techniques are useful as effective tools to evaluate the insulation condition of the machines. The experimental results will be introduced and discussed in this paper.