High Frequency Transient Voltage Research Articles

High Frequency Transient Sparse Measurement-Based Fault Location for Complex DC Distribution Networks

Measurement points supporting data high-speed communication in complex dc distribution networks are insufficient, meanwhile, fault characteristics are greatly affected by control strategies of power electronic equipment. These may cause failure of traditional fault location methods when applied to complex dc distribution networks. Thus, this paper proposes a novel dc pole-to-pole short-circuit fault location algorithm for complex dc distribution networks. First, according to the high frequency transient current loops, this paper constructs the high frequency impedance equivalent models of module multilevel converter (MMC) and dc/dc converter, which are not affected by the control strategies and offer stable impedance values during fault process. Then high frequency transient voltages of sparse measurement points are extracted by wavelet transform to form the node high frequency transient voltage equation. Finally, the node high frequency transient current sparse vector is solved to locate fault position by the node high frequency transient voltage equation combined with the Bayesian compressed sensing (BCS) theory. The proposed algorithm has low requirements on the number of measurement points and does not require data to be measured strictly synchronously. It is also not affected by converter’s control strategies and transition resistances. A 32-node dc distribution network is built in PSCAD/EMTDC and simulation results verify the accuracy of the proposed location algorithm.

A Earth Fault Section Identification Method Based on ANN

The method to discriminate the fault within or beyond the protective zone according to the signals with high frequency detected in protection has problem with low reliability when the resistance of earth fault is high. The transient voltage with low frequency detected in protection can reflect the size of fault intensity approximately, and the transient voltage with high frequency detected in protection in internal fault is bigger than that in external fault when the size of fault intensity is same. The high frequency transient voltage and low frequency transient voltage detected in protection are chosen as inputs and fault section as outputs for training and testing the neural network for fault identification in the UHVDC transmission line, fault section can be identified when input fault characteristic data to the trained model. A variety of transmission line earth fault situation are simulated by PSCAD, and this earth fault section identification method based ANN shows satisfactory performance, even the fault resistance is high.

The Identification of Internal and External Faults for ±800kV UHVDC Transmission Line Based on S-Transform and SVM

There is a smoothing reactor and DC filter between the inverter and the direct current line to form a boundary in the HVDC transmission system. Since this boundary presents the stop-band characteristic to the high frequency transient voltage signals, the high-frequency transient voltage signal caused by external faults through boundary will be attenuated and the signals caused by internal faults will be unchanged. In this paper, a new technique in which the combination of the S–transform and support vector machine (SVM) is used to analyze the transient signals, is proposed for distinguishing internal faults from the external faults based on the significantly difference of high-frequency transient voltage on the point of protection.

Ground Fault Location on a Transmission Line Using High-Frequency Transient Voltages

This letter presents a fault-location method using high-frequency transient voltages generated by ground faults on a transmission line. The method is based on the measurement from one end of the line. The fault location is determined solely from the arrival time of initial waves of modal voltages at the measuring bus. The method does not need to use the reflected waves. The method is tested using the Electromagnetic Transient Program and the statistical results are presented.

Transformer Response to System Switching Voltages

A section of an actual power system was modelled on a Transient Network Analyzer for the purpose of defining high frequency transient voltages occuring during switching events. The variety of system switching events which were staged produced oscillatory voltages covering a broad band of frequencies. On a digital model of the system autotransformers it was demonstrated that such oscillatory voltages could excite internal natural frequencies, but none of the actual generated waves coincided closely with the particular transformer natural frequency. However, if the applied waveshapes were frequency-scaled to a closer match, internal response voltages of concern could be developed.

Transient Voltages on Power Station Wiring

The paper presents the results of measurements on the characteristics of high frequency transient voltages on power station wiring. The characteristics described are the amplitude, frequency, impedance, coupling properties and rate of occurrence. The control measures investigated include the use of shielded cables, relocation of wiring grounds and use of surge diverting capacitors.

High-frequency transient voltage measuring techniques

Transient voltages continue to cause insulation failures of transformers in a variety of applications. There is evidence that some voltage transients may include frequency components up to 100 mc (megacycles) of substantial peak-to-peak amplitude. Conventional techniques for securing reasonably accurate oscillographic recordings of high-frequency transients were found to be inadequate. Systems were devised which couple the oscillograph to the point of voltage measurement by 50-ohm cables. Through the combination of special signal-cable filters and relatively simple shielding techniques, the effects of spurious signals upon the oscillographic recording of high-frequency transient voltages can be virtually eliminated.