Nowadays, the electric industry develops its activities in a business environment characterized by competitive markets and regulatory authorities that demand strict technical requirements, imposing severe penalties when unfulfilled. This context drives electric utilities to optimize the management of their physical assets without decreasing their reliability. In such situation, instrument transformers are important assets playing a critical role in HV power networks. This is so that failures in this equipment, results in unplanned outages affecting the operation of transmission networks and reliability in electricity delivery. This paper presents a practical approach developed to define priority criteria for the replacement of instrument transformers installed in the HV network of Edenor, the largest argentine electric distribution utility. To do so, focus was placed on defining a methodology to prioritize the replacement of critical units installed. As a result, Reliability Indices of the whole instrument transformers population were developed. So, priorities for the replacement of units are defined considering the risk assessment of the HV network as a whole. The developed methodology, led to an on-going process subjected to regular adjustments and improvements from the data obtained. By using of this data management approach, positive results have been reached, enhancing the condition assessment of the instrument transformers population and the reliability of the HV network.