Figs. 3
,
4
and
5
as well.
Pearson correlation coefficient for RLC ladder network and MTL model for 10 kHz < f < 1MHz
Pearson correlation coefficient for RLC ladder network and MTL model for 10 kHz < f < 1MHz
Pearson correlation coefficient for RLC ladder network and MTL model for 1MHz < f < 5MHz
Pearson correlation coefficient for RLC ladder network and MTL model for 1MHz < f < 5MHz
5. Result of PD Localization
In order to estimate the location of PD in generators with more reliability, it is better to verify the accuracy of the models that will be used in PD localization first. So it is recommended to measure and record the frequency spectrum of the generator in the first step. Then the simulation results must be compared with the measurements. If simulation results were satisfactory, the models can be used for PD localization. Otherwise the models must be modified or the parameters of the model must be optimized before PD localization.
At the first, PD pulses have been injected by the PD calibrator in the different part of the winding. Then the current signals measured/simulate in the end of the winding. These PD signals have been generated in kHz and MHz frequency range that used for RLC ladder network and MTL models respectively.
Fig. 6
shows the PD pulse studies circuit in a laboratory. The PD pulse to be generated in the kHz range has been shown in
Fig. 7
.
Figs. 8
,
9
show the comparison between the current spectrum for RLC model and measurements results. The PD pulse to be generated in the MHz range has been shown in
Fig. 10
. The
Figs. 11
,
12
show the comparison between the current spectrum for MTL simulated model and measurements results.
PD pulse measured in circuit in a laboratory
The PD pulses measured in the kHz range (the PD has been injected in node 6)
The comparison of current and the spectrum (PD has been injected in node 1 for RLC ladder network model)
The comparison of current and the spectrum (PD has been injected in node 6 for RLC ladder network model)
The PD pulses measured in the MHz range (the PD has been injected in node 6)
The comparison of current and the spectrum (PD has been injected in node 1 for MTL model)
The comparison of current and the spectrum (PD has been injected in node 6 for MTL model)
In this section from the frequency spectrum of the current signals, and poles estimate of the system, the location of PD can be estimated along the winding. Then these results compared with real position.
Table 5
shows the comparison between the real position and the simulated estimated position of PD (Depending to the node).
Comparison between real position and the simulation estimated position of PD
Comparison between real position and the simulation estimated position of PD
6. Conclusion
This paper compared the measurement and simulation results of transient over voltages and then partial discharge localization in the windings of a 6kV/250kW generator. Voltages along the generator windings were simulated by applying MTL and RLC ladder network theory. The results of the transients voltage calculated in the coils of the winding were compared with laboratory measurement. A relatively good correlation observed between measurement and RLC Ladder Network model simulation results for the frequency range of 10kHz < f < 1MHz. However in the range of the frequency 1MHz < f < 5MHz, the MTL model, provides a better agreement between the simulated and the measured voltages.
An algorithm for partial discharge localization has been developed in this paper. The approach is based upon frequency spectrum analysis of PD current signals. PD pulses have been injected by the PD calibrator in the different part of the winding. Then the PD signals measured or simulate in the end of the winding. These PD signals have been generated in kHz and MHz frequency range that used for RLC ladder network and MTL models respectively. A relatively good correlation have been observed between measurement and RLC ladder network model simulation results for the frequency range of kHz (10kHz < f < 1MHz), however in the frequency range of MHz (1MHz < f < 5MHz), the MTL model have been provided the better agreement between the simulated and the measured for PD Location.
BIO
S. M. Hassan Hosseini was born in Tehran, in 1969. He received the B.Sc degree in electrical power engineering from Mashhad Ferdowsi University, Mashhad, Iran in 1993. He received the M.Sc and Ph.D degrees in electrical power engineering in 2000 and 2005 from Islamic Azad University South-Tehran Branch and Science & Research Branch, Tehran, Iran, respectively. His research interest is transient modeling of transformers and generators, Partial Discharge, High Voltage Engineering.
S. M. Hosseini Bafghi was born in Bafgh, Iran, in 1986. He received the B.Sc. and M.SC degrees in electrical power engineering from Islamic Azad University of Mehriz and South Tehran Branch in 2009 and 2013 respectively. Since 2011, He joined as a lecturer of Electrical Engineering Department, Faculty of Engineering Islamic Azad University Bafgh Branch. His research interest is transient and PD modeling of Generators.
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