Data Acquisition, Monitoring, Calibration, P&c Health and Event Analysis In Digital Substations

Data acquisition, monitoring and calibration in digital substations is affected by the recent technological advances. The digital substation is defined as a substation with data acquisition separated from relays and other devices; specifically, data acquisition is performed by merging units. Merging units offer both data acquisition and control through the control unit. Merging units in the digital substation allow high sampling rates, 80 samples per cycle as well as 256 samples per cycle. These sampling rates cover 99.9% of applications in a power system, from power quality applications to protection control and operation. As for any data acquisition system, the merging unit based digital substation system must be calibrated and provide validated data under any operating conditions of the system and enable fast view and analysis of events. The technology enables the tasks of calibration, validation, error correction and instrumentation anomalies via software without interfering with the operation of the system. The paper will present the software based real time calibration, validation, error correction and detection of instrumentation anomalies such as hidden failures. These capabilities make the digital substation a truly intelligent system that guarantees calibrated and validated data under any power system operating conditions. The integrated system can be characterized as a monitoring system of the health of the data acquisition system. The paper will discuss the analytics that enable detection of any hidden failures as well as the location of the hidden failure via hypothesis testing embedded in a dynamic state estimation of the entire substation protection and control system. This approach has been tested via numerical experiments with hardware-in-the-loop and establishes a new paradigm of asset management for protection and control systems which increases the reliability of these systems. The paper will present use cases with detailed results. One case represents an actual hidden failure that caused a local blackout following a minor fault that was successfully cleared.