การปรับปรุงข้อมูลจากเครื่องบันทึกเหตุผิดพร่องและการศึกษาอิมพิแดนซ์ลัดวงจรในระบบส่ง / วาที เลาหะโรจนพันธ์ = Data refinement of fault recorders and examination of fault impedances in a transmission system / Vatee Laoharojanaphand
The standard one- and two-terminal fault location algorithms may require pre-processing of the sampled data from digital fault recorders (DFR). The quality of raw data which depends partly on the accuracy of the involved instrument transformers can therefore affect performance those algorithms, especially when employing data from a few associated measuring devices. This thesis presents a data refinement process for fault data recorded by a group of associated DFR for improving accuracy in line fault location in a transmission system. The refinement process employs weighted least square state estimation technique to compute calibration factors, using the measurements of pre-fault data of voltage and current from multiple correlated DFRs. The factors then are applied to correcting the corresponding during-fault data. To verify the effectiveness of the proposed refinement method, both simulated data from the IEEE 14 bus test system and field measured data from the Thailand’s transmission system have been tested using the standard two-terminal fault location algorithm. Test results strongly confirm that the improved accuracy in locating fault on a transmission line can be obtained when compares to the respective unrefined cases. In turns, the results of the two-terminal fault location analysis are used to examine the characteristics of the fault impedances experiencing in the transmission network. Based upon the 20 case studies in this thesis, it finds out that the fault impedance can be quite different from a purely resistive model normally assumed in previous literatures
