Masatake Kawada

Visualization of Contact Vibration generated on Turbine Model using Fast Haar Wavelet Transform

In this paper we present the results of fundamental study to introduce the in-place fast Haar wavelet transform to vibration diagnosis for a turbine and a generator. It is required to detect typical vibration of the turbine and the generator accurately. Modern power plants usually use one-high pressure and one or two lower pressure turbines. We made the turbine model with 3 rotors supported with journal bearings to simulate rotor-to-stator contact. The contact vibration was measured with displacement meters, acoustic emission sensors and accelerometers. The acceleration signals accompanied by the contact were visualized in the time-frequency domain by the in-place fast Haar wavelet transform. The in-place fast Haar wavelet transform can clearly detect the components accompanied by the contact

Discrimination of Vibration Phenomena on Model Turbine Rotor using In-Place Fast Haar Wavelet Transform

In this paper we present the results of applying the in-place fast Haar wavelet transform to visualization of vibration phenomena on a model turbine rotor. It is required to detect typical vibration of the turbine and the generator accurately. Modern power plants usually use one-high pressure and one or two lower pressure turbines. We made the model turbine with three rotors supported with journal bearings and simulated abnormal conditions. The vibrations accompanied by the abnormal conditions were measured with accelerometers, displacement meters and acoustic emission sensors. The acceleration signals were visualized in the time-frequency domain by the in-place fast Haar wavelet transform. The in- place fast Haar wavelet transform can clearly detect the components accompanied by the abnormal conditions.

Fundamental study on vibration diagnosis for turbine generators using wavelet transform

We presented results of the fundamental study to introduce the wavelet transform to the vibration diagnosis for turbine generators. It is required to detect the vibration of turbine generators more accurately. The wavelet transform is used in many fields because it is able to visualize a phenomenon in the time-frequency domain and to detect the beginning time and the duration of it. We made a model rotor supported with two journal bearings to simulate typical vibrations as contact vibration, clearance vibration, and oil whip. The vibration phenomena were measured with displacement meters at the rotor and accelerometers at the rotor bearing, and then, visualized in the time-frequency domain by the wavelet transform. It is found that the dynamic spectra obtained by the wavelet transform of the contact vibration, the clearance vibration, and the oil whip, are different respectively. Therefore, this method is able to distinguish the typical vibration phenomena. The vibration phenomena can be detected and distinguished at the early stage.

Measurement of electromagnetic waves emitted from partial discharge generated in PLG type-ground coil for superconducting Maglev

It is planned to start commercial service with Superconducting Magnetically Levitated Vehicle (Maglev) system between Tokyo and Nagoya (about 300km) in Japan in 2027. Combined propulsion, levitation and guidance (PLG) type-ground coil (PLG coil) has been developed in order to reduce the construction cost by reducing the number of ground coils. We measured the electromagnetic (EM) waves emitted from partial discharge (PD) generated in the PLG coil in order to develop the non-contact PD detection system for the PLG coils. This paper describes the measurement results of the EM waves emitted from PD generated in the PLG coil using UHF antennas and the location of PD by using the radio interferometer system.

Ultra wide band VHF/UHF radio interferometer system for detecting partial discharge source

The electromagnetic (E-M) waves emitted from partial discharge (PD) generated by material defects in high-voltage electric power apparatus and facilities are broadband signals including VHF/UHF components. In this paper, the author proposes an ultra wide band VHF/UHF radio interferometer system (UWB-VURIS) for detecting PD source, which has been originally designed, constructed and tested. The system is based on the idea extracting the phase differences at different frequencies between a pair of the received E-M signals by the fast Fourier transform (FFT) and computing the arrival angle of the E-M waves emitted from PD source. It can be small-sized, more suitable for compact and portable systems. It is able to reduce the operating time at the measurement site because it is not needed to arrange many antennas at the many points. The indoor test results indicate that the UWB-VURIS is able to estimate the arrival angle of the E-M waves emitted from PD source.

Internal defect position evaluation of the ground coil by detecting the electromagnetic waves from the partial discharge

As a huge number of ground coils will be used outdoors for a long time in the superconducting magnetically levitated transportation (Maglev) system, a reduction in ground coil cost with high reliability will be required. Especially the propulsion coil needs the high insulation stability as the high-voltage equipment. On the other hand, as it is assumable that the ground coil has the resin molded winding coil with coreless construction, the ground coil must be exposed to the severe environment where it receives electromagnetic force directly. Therefore, there is a possibility that minute defects that are latent in the mold construction of the ground coil may expand, become apparent and cause of deterioration of the insulation stability. In this paper, we examined the insulation diagnostic measures to assess the existence/nonexistence of the inside defect and locate the defect position by setting a simulated defect artificially inside the mold construction of the ground coil and detecting the electromagnetic waves effectively that are generated from the discharge at the defect point.

Time-Frequency Analysis of EM Waves Emitted from Consecutive PD Pulses Using the Constrained Interpolation Profile (CIP) Method and the In-Place Fast Haar Wavelet Transform

Analysis of the electromagnetic (EM) waves emitted from partial discharge (PD) is useful from the viewpoint of non- contact diagnosis for power equipment. Its important to model the generation and propagation of the EM waves emitted from PD for understanding the physical mechanism. Maxwells equations for the EM waves are replaced by a set of finite difference equations such as the finite-difference time-domain (FDTD) method. The FDTD suffers from phase error caused by its numerical dispersion. We numerically analyzes the EM waves emitted from PD in time-frequency using the constrained interpolation profile (CIP) method, which is higher accuracy than the FDTD, and the in-place fast Haar wavelet transform (IP-FHWT). Numerical results show that the proposed method based on the CIP and the IP-FHWT is useful for analyzing the relationship between the consecutive PD pulses and the EM waves.

Locating partial discharge generated in PLG type-ground coil for superconducting Maglev using radio interferometer system

Superconducting Magnetically Levitated Vehicle (Maglev) system needs a number of ground coils installed on the guideway, which corresponds to the rails of a conventional railway. In order to reduce the construction cost by reducing the number of ground coils, a combined propulsion, levitation and guidance (PLG) type-ground coil (PLG coil) has been developed. Because the main insulating material of PLG coil is epoxy resin, it is required to develop the insulation diagnosis technique for the ground coils installed along the entire length of the guideway. We apply the radio interferometer system, which has been originally designed, to locate partial discharge (PD) generated in the PLG-coil. The radio interferometer system can locate PD by calculating the time difference of arrival of EM waves emitted from PD. This paper describes the results of PD location by using the radio interferometer system set at three positions in turn and the effect of position.

Simulation on locating partial discharge in T-shaped branch of GIS by applying the STA/LTA ratio method to EM waves leaked from insulating spacers

This paper describes partial discharge (PD) location through electromagnetic (EM) waves in ultra-high frequency (UHF: 300MHz-3GHz) band leaked from the insulating spacers in a T-shaped branch of gas insulated switchgear (GIS). The propagation of EM waves in GIS and the leakage through spacers were simulated by using the finite difference time domain (FDTD) method. The time difference of arrival (TDOA) of leaked EM waves was employed to locate PD under white noise background. The short-term-average to long-term-average (STA/LTA) ratio method was applied to estimate TDOAs among the monitoring points arranged on the circumference of the insulating spacers in a connection of the next section of GIS. The simulation results showed that PD position could be located through the EM waves leaked from spacers of GIS wherever PD in a T-branch or straight section. The average location error of PD in the T-branch was larger than that of PD in the straight section. The PD positions and pairing of monitoring points had little influence on the location accuracy. Finally, the influence of flanges and bolts on PD location was investigated.

Visualization of vibration phenomena on model turbine rotor using cross-correlation method based on in-place fast Haar wavelet transform

In this paper we present the results of applying the cross-correlation (CC) method based on the in-place fast Haar wavelet transform (IpFHWT) to know the correlation between the received signals associated with vibration phenomena on a model turbine rotor. It is required to detect typical vibration of turbine and generator accurately. Modern power plants usually use one-high pressure and one or two lower pressure turbines. We make the model turbine with three rotors supported with journal bearings and simulated abnormal conditions. The vibration caused by the abnormal conditions is measured with accelerometers, displacement meters, and acoustic emission sensors. The cross-correlation of acceleration signals is obtained in the time-frequency domain by using the CC-IpFHWT.