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A well-monitored and reasonable-assessed protection system can lead to the improved operation and reliability of power systems. In this paper, a systematic and efficient operation condition assessment (OCA) method and its practical implementation for protection systems are proposed. Considering the device configuration and information transmission scheme, a protection system operation condition model (PSOCM) is developed. Based on the PSOCM, an OCA method is designed to assess the statuses of devices, information flows, information transmission branches, and relay functions. To verify the effectiveness of the proposed method, a master-substation operation condition assessment system (MS-OCAS), which utilizes real-time monitoring and other raw data, is demonstrated. As shown by the experimental results for a 110 kV IEC 61850-based substation, the proposed method, and system can realize the whole-view OCA of protection systems and can dramatically increase the maintenance efficiency.

Several incidents of transient power converse due to the interaction of AC/DC system have been reported recently, and the incidents result in the malfunction of directional comparison pilot protection (DCPP) and the miss-trip of vital AC transmission lines. Taking Jingling-Echeng HVDC and its connected inverter side AC system into account, the corresponding electromagnetic transient simulation model is established in PSCAD/EMTDC based on the operating environment of a mal-operation incident. The response characteristics of HVDC system and the fault features of AC system are studied in this paper while faults occur at the inverter side AC system on the basis of the analysis of the real recorded fault data. Results show that the rapid response of HVDC results in the malfunction of DCPP while AC fault occurs. The mechanism of transient power converse and the variations of AC fault features are analyzed. The corresponding measures are also proposed. Index Terms--directional comparison pilot protection (DCPP); fault feature; high-voltage direction current (HVDC); power converse; transient.

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