The reliable operation of high voltage circuit breakers (HVCBs) is crucial for ensuring the security of the power system. Therefore, the accurate calculation of the health index (HI) for proper maintenance of HVCBs is essential. However, existing methods often neglect two key challenges: proper signal preprocessing for feature extraction and incorporating measurement accuracy into the HI model. This paper addresses these shortcomings by proposing a methodology for improving HI representation for HVCBs. We account for measurement accuracy by considering the varying precision of different monitoring schemes. Furthermore, the impact of signal preprocessing on the condition monitoring data is analyzed. Finally, a case study exhibits how the HI based failure rate can affect the reliability centered maintenance scheduling in the power system.