Detection and location of internal defects in the insulation of power transformers

Fuhr, J.; Haessig, M.; Boss, P.; Tschudi, D.; King, Robert

doi:10.1109/14.249379

Cited by 64 publications

(19 citation statements)

References 5 publications

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“…The mean transit time in a bar is 28.2 ns for a bar length of 2.3 m. Thus, the velocity of the fast mode is 81. 6 , or 27% of the speed of light. The velocity of the fast mode is determined by , where is the speed of light, is the relative dielectric constant (typically is 4-6 for epoxy-mica insulation), and is the relative permeability.…”

Section: A Analysis Of the "Slow Mode" And The "Fast Mode"mentioning

confidence: 99%

“…During the long path from the discharge site to the terminals, where the discharge can be measured, the signal is heavily distorted. For transformers, it is shown in [4]- [6] that the PD signal propagates in three modes: i) the higher frequencies (0.1 to 10 MHz) travel through the capacitive ladder network, formed by the interturn capacitances, ii) a traveling-wave mode (frequencies up to 10 kHz) follows the transmission line formed by the galvanic path of the winding, and iii) an oscillating component is determined by the internal resonant frequencies of the transformer (10 to 100 kHz). As a consequence, the amplitude and waveform of the response at the terminal strongly depends on the location of the discharge and on the design of the transformer.…”

mentioning

confidence: 99%

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Propagation of Partial Discharge Signals in Stator Windings of Turbine Generators

Pemen

Laan

Leeuw

2006

IEEE Trans. On Energy Conversion

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Abstract-We studied the propagation of partial discharge pulses in a stator winding by means of measurements on a dismantled 35-MW generator and found that a stator winding acts as a transmission line. Therefore, a partial-discharge (PD) signal manifests itself at the generator terminals after a transit time that depends on the location of the discharge. Due to capacitive and inductive couplings in the end-winding region, a second propagation mode is present for higher frequencies. This "fast mode" manifests itself at the terminals without appreciable time delay. The capacitive and inductive couplings also cause crosstalk between the phases. As a consequence, a signal measured in one phase does not necessarily originate from a discharge in that phase. The amplitudes of the fast mode and, to a lesser extent, the slow mode (or transmission-line mode) are heavily damped when the discharge occurs further away from the measuring terminal. The consequence is that only discharges close to the measuring terminal can be observed. The propagation of a PD signal is not only influenced by the construction of the generator but also by its external connections.

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Section: A Analysis Of the "Slow Mode" And The "Fast Mode"mentioning

confidence: 99%

mentioning

confidence: 99%

Propagation of Partial Discharge Signals in Stator Windings of Turbine Generators

Pemen

Laan

Leeuw

2006

IEEE Trans. On Energy Conversion

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“…In addition, UV cannot detect the discharge when there is confusion between the UV detection device and the discharge source. With the development of the piezoelectric sensing technique, acoustic sensors can be produced with high sensitivities, good anti-interference abilities as well as micro-scale packaging; these sensors have great potential in many applications, including PD detection [8][9][10][11]. The acoustic waves excited by corona discharge have frequencies of up to 300 kHz with strong directivities, and they can result in different responses from the sensors placed in various positions in a plane.…”

Section: Introductionmentioning

confidence: 99%

Positioning and Imaging Detection of Corona Discharge in Air with Double Helix Acoustic Sensors Array

Dong

Ren

et al. 2017

Energies

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Corona discharge could be a serious hazard to the outdoor insulation of a high-voltage (HV) system and also is an important detection issue for insulation status diagnosis. In this study, a double-helix-ultrasonic-array (DHUA) sensor was developed for corona positioning, which showed a good sensitivity to the ultrasonic signal originating from corona discharge and a satisfied directional response in static beam patterns. Based on the matting-based image fusion method, the acoustic intensity matrix was fused to a visual scene in real-time. This ultrasonic visualization technology was then evaluated with a simulation test and performed in a real air insulated substation (AIS), and showed a satisfied performance in terms of sensitivity and spatial location resolution.

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“…Extensive experiments have introduced PD locating techniques by integration process of signals from AE sensors installed on power transformer tank wall [2], [3]. Nowadays, application of UHF sensors is also widely promoted for better locating resolution as well as for higher signal to noise ratio [4].…”

Section: Introductionmentioning

confidence: 99%

A proposal for Hybrid PD sensor identifying absolute distance from PD source

Kim

Hikita

2013

2013 Annual Report Conference on Electrical Insulation and Dielectric Phenomena

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In this paper, the authors proposed a Hybrid PD (AE) sensor which could tell us an absolute distance from PD source. The proposed sensor installed at one fixed position of power transformer tank wall could detect HF signal and ultrasonic one simultaneously. Ignoring faster arrival time of HF signal, an approximated absolute distance from PD source could be derived easily. Moreover, applying time series measurement to the scheme, a pair of PD signals could enable us to discriminate true PD signals from noise spectra. This paper also shows the laboratory experimental results from an oil transformer of 6 kV.

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Detection and location of internal defects in the insulation of power transformers

Cited by 64 publications

References 5 publications

Propagation of Partial Discharge Signals in Stator Windings of Turbine Generators

Propagation of Partial Discharge Signals in Stator Windings of Turbine Generators

Positioning and Imaging Detection of Corona Discharge in Air with Double Helix Acoustic Sensors Array

A proposal for Hybrid PD sensor identifying absolute distance from PD source

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