What is the primary function of a data historian in a power plant's data acquisition system?

The primary function of a data historian in a power plant's data acquisition system is to collect, store, and retrieve large volumes of time-series data generated by the plant's various sensors, control systems, and equipment. This data includes process variables, equipment status, alarms, and operator actions. The historian is designed to efficiently handle high data rates and long-term storage, typically storing data for months or years. The data stored in the historian is used for a variety of purposes, including performance monitoring, troubleshooting, root cause analysis, regulatory reporting, and optimization. By analyzing historical data, engineers and operators can identify trends, diagnose problems, and improve plant performance. The data historian provides a comprehensive record of the plant's operation, enabling informed decision-making and continuous improvement.