Electrical tree growth and partial discharge in epoxy resin under combined AC and DC voltage waveforms

Iddrissu, Ibrahim; Rowland, S. M.; Zheng, Huzhi; Lv, Zepeng; Schurch, Roger

doi:10.1109/tdei.2018.007310

Cited by 42 publications

(21 citation statements)

References 19 publications

(30 reference statements)

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“…The greater part of research regarding AC-DC superposition and PD is motivated by the AC ripple of voltage source converters of the HVDC transmission systems. Subsequently, typical defects such as voids in polymeric insulators [4][5][6], voids in oil-pressboard arrangements [7] and electrical treeing [8][9][10][11] were investigated. In general, it was found that the AC component dominates the PD behavior and the literature findings can be summarized as follows:…”

Section: Literature Reviewmentioning

confidence: 99%

Partial Discharge Behavior of Epoxy-Mica Insulation System under Superimposed AC and DC Voltage Stress

Linde

Backhaus²,

Schlegel³

et al. 2022

NORD-IS

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Recent technology advances in wind energy conversion systems include a new type of permanent magnet synchronous generator with a segmented stator that allows lightweight concepts with high efficiency and superior controllability. Each stator segment is driven by a separate power converter. The various cascaded power converters can be connected in series and in parallel, which ultimately leads to the superposition of a DC and an AC voltage stress in the insulation of the stator coils. The resulting DC-AC mixed voltage is an entirely new electrical stress for the epoxy-mica insulation system that is typically utilized as main insulation of rotating electrical machines. In order to resemble this stress, typical dielectric tests such as partial discharge (PD) measurements and long-term aging of model insulation systems have to be be carried out under DC-AC mixed voltage stress. The mentioned investigations are presented in this contribution. The results indicate that the AC voltage is dominant with regard to the PD inception and influences the PD parameters such as the apparent charge and the repetition rate substantially when compared to the DC voltage proportion. The accelerated aging tests with significantly higher AC-DC mixed voltage stress than is expectable under operating conditions revealed no measurable PD deterioration of the investigated insulation systems.

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Section: Literature Reviewmentioning

confidence: 99%

Partial Discharge Behavior of Epoxy-Mica Insulation System under Superimposed AC and DC Voltage Stress

Linde

Backhaus²,

Schlegel³

et al. 2022

NORD-IS

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show abstract

“…In most of the reports about electrical treeing at industrial frequency, different trends had been found, including periods when negligible PD activity was measured. [1], [20], [53]. The difference between VLF and 50 Hz in the behaviour of times series of PD amplitude could be related with the charge relaxation or charge transport phenomena in PDs [32], [38], [39], [54]: with a lower excitation frequency the electric charge has more time for recombination, which reduces the possibilities of discharge extinction due to deposition of cations in sidewalls of the tree [1].…”

Section: A Pd Time Series and Electrical Tree Growthmentioning

confidence: 99%

Analysis of Partial Discharges in Electrical Tree Growth Under Very Low Frequency (VLF) Excitation Through Pulse Sequence and Nonlinear Time Series Analysis

et al. 2020

Self Cite

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Electrical treeing is the main degradation mechanism in high voltage polymeric insulation, that leads to power system plant failure and the loss of electricity supply. Electrical trees grow under partial discharge (PD) activity, which can be measured and analyzed to understand and characterize electrical tree growth. In this work, PD measurements were analyzed for electrical trees grown in epoxy resin needleplane samples under very low frequency (VLF, 0.1 Hz) voltage excitation. VLF is interesting as it is used for testing power cables and other high capacitance insulation loads. However, more experience and new methods are needed for PD interpretation. PDs were studied using two tools: pulse sequence analysis (PSA) and nonlinear time series analysis (NLTSA) from dynamic system theory. PSA was treated here as a particular case of NLTSA since their constructions are similar in their mathematical treatment. The experimental results showed that electrical trees grown at VLF had branch-type structure and times to breakdown about fifty times larger than samples aged at industrial frequency. PSA plots were compared with 2D projections of state-space trajectories that represent the dynamics of the nonlinear system (NLTSA approach). In terms of graphical representation, NLTSA 2D projections generated more clusters than the PSA plots, thus, it was interpreted that NLTSA revealed more details about the nonlinear dynamic system associated with electrical tree growth. On the other hand, using the NLTSA approach, the correlation dimension was estimated to characterize the electrical tree growth. The results showed a different evolution obtained for VLF excitation compared to the results reported for test samples aged at industrial frequency in other studies.

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“…The probability of the generation of multiple-branch trees decreased with increasing temperature. In [27], a relationship between the electrical tree growth process and PD was found. Different tree structures and growth stages are associated with different PD characteristics.…”

Section: Introductionmentioning

confidence: 99%

Effects of Temperature Gradient on Electrical Tree Growth and Partial Discharge in Silicone Rubber Under AC Voltage

et al. 2020

IEEE Access

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The Joule heat produced by the current in conductor decreases in the radial direction, producing a temperature gradient in the insulation. This existing temperature gradient can affect the electrical tree phenomenon in insulation materials because of the temperature dependence of insulation material, charge migration and tree growth. Different temperature gradients were obtained by controlling the temperature of high voltage (HV) and ground electrode (GD) sides. The electrical tree was recorded by a microscope, while the partial discharge (PD) was observed simultaneously. For better understanding the effects of the temperature gradient on electrical tree inception, the trap distribution in silicone rubber (SIR) with different temperature was analyzed by isothermal discharge current (IDC) method. With the fixed temperature in HV or GD side, it was found that the electrical tree inception voltage decreased linearly with increasing temperature in either side. The IDC results indicate that the increasing temperature contributes to the de-trapping of charges and lowers the inception voltage. Besides, the electrical tree length and accumulated damage gradually increase with the temperature gradient. The observed PD amplitude and quantity also increase with the temperature gradient, which facilitates the growth of electrical trees. These results indicate that the tree growth is promoted with an increase in the temperature gradient of the cable insulation, posing a threat to the safety of the cable system. INDEX TERMS AC plastic cable, cable accessories, silicone rubber, electrical tree, temperature gradient, tree inception, growth characteristics, partial discharge.

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Electrical tree growth and partial discharge in epoxy resin under combined AC and DC voltage waveforms

Cited by 42 publications

References 19 publications

Partial Discharge Behavior of Epoxy-Mica Insulation System under Superimposed AC and DC Voltage Stress

Partial Discharge Behavior of Epoxy-Mica Insulation System under Superimposed AC and DC Voltage Stress

Analysis of Partial Discharges in Electrical Tree Growth Under Very Low Frequency (VLF) Excitation Through Pulse Sequence and Nonlinear Time Series Analysis

Effects of Temperature Gradient on Electrical Tree Growth and Partial Discharge in Silicone Rubber Under AC Voltage

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