Influence of Repetitive Square Voltage Duty Cycle on the Electrical Tree Characteristics of Epoxy Resin

The application of wide band-gap power electronic devices brings more challenges to insulating packaging technology. Knowing the influence of applied voltage parameters on insulation performance is helpful to evaluate the insulation condition of electric power equipment. In this paper, the effect of repetitive square wave voltage duty cycle on the growth characteristics of electrical trees in epoxy resin was studied. The experimental results show that the square wave voltage duty cycle has a significant influence on treeing features. The electrical tree proportion initiation has shown a decreasing trend, and the shape of the electrical tree changes from pine-like to branch-like by increasing the duty cycles. The length and damaged area of electrical tree increased with the increase in the duty cycle up to 10% and then decrease by increasing the duty cycle higher than 30%. It indicates that a low duty cycle will enhance the electron injection and accumulate space charges and thus accelerate electrical tree development. Under short duty cycles, the electric field due to the shielding effect near the needle tip suppresses the electrical tree growth, which results in treeing growth stagnation. The obtained results are helpful to keep these parameters in mind during the design of epoxy-based insulation such high-voltage rotating machines and power electronic device packaging.

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Effect of Air Gap on Electrical Tree in Epoxy Resin Under High Frequency Bipolar Square-Wave Voltage

Materials ◽

10.3390/ma13245722 ◽

2020 ◽

Vol 13 (24) ◽

pp. 5722

Author(s):

Shihang Wang ◽

Chuang Zhang ◽

Hang Fu ◽

Jiao Xiang ◽

Jianying Li ◽

...

Keyword(s):

Epoxy Resin ◽

High Frequency ◽

Air Gap ◽

Heat Accumulation ◽

Air Gaps ◽

Square Wave ◽

Electrical Tree ◽

Electrical Trees ◽

Voltage Frequency ◽

Tree Characteristics

Insulation fails quickly under high-frequency AC high voltage, especially bipolar square-wave voltage with a high dV/dt. It is of great significance to study the failure mechanism of epoxy casting insulation under such kind of voltage. In this paper, pin-plane epoxy casting insulation samples with air gaps were prepared, and the relation between the electrical trees under the high frequency bipolar square-wave voltage and the air gap conditions and voltage frequencies (1~20 kHz) were studied. Results indicated that, with the presence of air gaps, the electrical trees were bush-type and had a relatively slow growth rate, which was different from the fast-growing branch-type trees in the samples without air gap. The electrical tree characteristics related with the size of air gap and voltage frequency were also studied. The electrical tree grew faster under higher voltage frequency or with a smaller air gap. Results proved that discharge introduced a lot of defects for the surface layer of the epoxy resin samples and hence induced the possibility of multi-directional expansion of electrical trees. In addition, the resulting heat accumulation and unique charge transport synergistically affected the electrical tree characteristics under the high frequency bipolar square-wave voltage.

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Application of the Gaussian Mixture Model to Classify Stages of Electrical Tree Growth in Epoxy Resin

Sensors ◽

10.3390/s21072562 ◽

2021 ◽

Vol 21 (7) ◽

pp. 2562

Author(s):

Abdullahi Abubakar Mas’ud ◽

Arunachalam Sundaram ◽

Jorge Alfredo Ardila-Rey ◽

Roger Schurch ◽

Firdaus Muhammad-Sukki ◽

...

Keyword(s):

Epoxy Resin ◽

Gaussian Mixture Model ◽

Mixture Model ◽

Tree Growth ◽

Asset Management ◽

Gaussian Mixture ◽

Growth Stages ◽

Insulation Material ◽

Electrical Tree ◽

Electrical Trees

In high-voltage (HV) insulation, electrical trees are an important degradation phenomenon strongly linked to partial discharge (PD) activity. Their initiation and development have attracted the attention of the research community and better understanding and characterization of the phenomenon are needed. They are very damaging and develop through the insulation material forming a discharge conduction path. Therefore, it is important to adequately measure and characterize tree growth before it can lead to complete failure of the system. In this paper, the Gaussian mixture model (GMM) has been applied to cluster and classify the different growth stages of electrical trees in epoxy resin insulation. First, tree growth experiments were conducted, and PD data captured from the initial to breakdown stage of the tree growth in epoxy resin insulation. Second, the GMM was applied to categorize the different electrical tree stages into clusters. The results show that PD dynamics vary with different stress voltages and tree growth stages. The electrical tree patterns with shorter breakdown times had identical clusters throughout the degradation stages. The breakdown time can be a key factor in determining the degradation levels of PD patterns emanating from trees in epoxy resin. This is important in order to determine the severity of electrical treeing degradation, and, therefore, to perform efficient asset management. The novelty of the work presented in this paper is that for the first time the GMM has been applied for electrical tree growth classification and the optimal values for the hyperparameters, i.e., the number of clusters and the appropriate covariance structure, have been determined for the different electrical tree clusters.

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Electrical Trees in a Composite Insulating System Consisted of Epoxy Resin and Mica: The Case of Multiple Mica Sheets For Machine Insulation

Engineering, Technology & Applied Science Research ◽

10.48084/etasr.468 ◽

2014 ◽

Vol 4 (4) ◽

pp. 662-668 ◽

Cited By ~ 2

Author(s):

V. A. Kioussis ◽

M. Danikas ◽

D. D. Christantoni ◽

G. E. Vardakis ◽

Α. Bairaktari

Keyword(s):

Cellular Automata ◽

Epoxy Resin ◽

Partial Discharges ◽

Experimental Results ◽

Rotating Machine ◽

Electrical Tree ◽

Electrical Trees ◽

Simulation Results

Epoxy resin and mica sheets consist the essential insulation of rotating machine stator bars. Such an insulation, although very resistant to partial discharges, is subjected to considerable electrical stresses and consequently electrical trees may ensue. In this paper, an effort is made to simulate electrical tree propagation in multiple epoxy resin/mica sheets with the aid of Cellular Automata (CA). An attempt to compare the simulation results with experimental results is also made.

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Electrical Tree Characteristics of Epoxy Resin under Bipolar Square Wave Voltage

2020 IEEE 3rd International Conference on Dielectrics (ICD) ◽

10.1109/icd46958.2020.9341976 ◽

2020 ◽

Author(s):

Hang Fu ◽

Chuang Zhang ◽

Jiao Xiang ◽

Zhuolin Cheng ◽

Shihang Wang ◽

...

Keyword(s):

Epoxy Resin ◽

Square Wave ◽

Electrical Tree ◽

Tree Characteristics

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Effects of bipolar repetitive square wave voltage parameters on electrical tree characteristics of epoxy resin

Polymer Testing ◽

10.1016/j.polymertesting.2021.107371 ◽

2021 ◽

Vol 103 ◽

pp. 107371

Author(s):

Peng Wang ◽

Yiwen Chen ◽

Shakeel Akram ◽

Pengfei Meng ◽

Jerome Castellon ◽

...

Keyword(s):

Epoxy Resin ◽

Square Wave ◽

Electrical Tree ◽

Tree Characteristics

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Effect of Bipolar Square Wave Voltage with Varied Frequencies on Electrical Tree Growth in Epoxy Resin

IEEE Transactions on Dielectrics and Electrical Insulation ◽

10.1109/tdei.2021.009355 ◽

2021 ◽

Vol 28 (3) ◽

pp. 806-814

Author(s):

Chuang Zhang ◽

Shihang Wang ◽

Hang Fu ◽

Zhuolin Cheng ◽

Jianying Li ◽

...

Keyword(s):

Epoxy Resin ◽

Tree Growth ◽

Square Wave ◽

Electrical Tree

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Acoustic-Reflex Dynamics for Pulsed Signals

Journal of Speech and Hearing Research ◽

10.1044/jshr.2102.295 ◽

1978 ◽

Vol 21 (2) ◽

pp. 295-308

Author(s):

Terry L. Wiley ◽

Raymond S. Karlovich

Keyword(s):

Duty Cycle ◽

Acoustic Impedance ◽

Normal Hearing ◽

Broadband Noise ◽

Threshold Shift ◽

Temporary Threshold Shift ◽

Acoustic Reflex ◽

Stapedius Muscle ◽

Duty Cycles

Contralateral acoustic-reflex measurements were taken for 10 normal-hearing subjects using a pulsed broadband noise as the reflex-activating signal. Acoustic impedance was measured at selected times during the on (response maximum) and off (response minimum) portions of the pulsed activator over a 2-min interval as a function of activator period and duty cycle. Major findings were that response maxima increased as a function of time for longer duty cycles and that response minima increased as a function of time for all duty cycles. It is hypothesized that these findings are attributable to the recovery characteristics of the stapedius muscle. An explanation of portions of the results from previous temporary threshold shift experiments on the basis of acoustic-reflex dynamics is proposed.

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