Chapter 5 Polymer Degradation and Its Measurement

EPR (sometimes annotated as ESR) has been carried out on functionalized nanoscale silica embedded in crosslinked polyethylene (XLPE) in comparison with the base resin. In situ EPR measurements under an applied electric field have been carried out, and the technique is outlined. The preliminary measurements show that EPR can detect trap sites in the bulk and interfacial polymer. In addition, EPR can detect texture in the polymer due to its processing. At the same time, measurements to determine the dynamics and spatial distribution of the space charge have been carried out under similar conditions using the pulsed electroacoustic analysis technique. The results are discussed in terms of the way in which the nanoparticles affect the local polymer environment.

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“…The principle of the EPR technique has been previously described by Wolter et al [5] and the configuration used here is depicted in Fig. 1.…”

Section: Experimental Arrangementsmentioning

confidence: 99%

The use of Electron Paramagnetic Resonance (EPR) in the probing of the nanodielectric interface

MacCrone

Nelson

Schadler

et al. 2007

2007 IEEE International Conference on Solid Dielectrics

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“…A mechanical stress that is applied for a prolonged period of time leads to physical aging of a polymer. This aging is manifested in two ways: (1) by causing formation of polymer radicals [53]; and (2) as an increase in the number and size of microvoids in the material [52]. Both of these consequences lower the dielectric strength of the materials, although quantitative data on PVC are lacking.…”

Section: Dielectric Strength Values Of Pvcmentioning

confidence: 99%

“…Minute metallic contaminant inclusions can cause 'extreme oxidative degradation' [66] and such metallic contaminants can act to produce initiation sites for electrical treeing [52]. Wolter et al [53] [66]. One might anticipate that antioxidants could improve the breakdown strength of a polymer, but studies on polyethylene [42] showed that, in fact, they act as an impurity and reduce the strength}a 1% add-on caused a 16% drop in breakdown strength; similar studies for PVC are not known.…”

Section: Chemical Degradationmentioning

confidence: 99%

Mechanisms and modes for ignition of low-voltage, PVC-insulated electrotechnical products

Babrauskas

2006

Fire Mater.

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SUMMARYPVC is the most common insulation material used for wiring in low-voltage (LV) service. 'Low-voltage', in the context of this paper, is taken to be 120-240 VAC. The electrotechnical products considered include insulated wires, cables and cords, and also appurtenant termination devices, e.g. male plugs or female taps. Well-known factors leading to the ignition of PVC-insulated wiring and related products include: (a) manufacturing defects; (b) grossly excessive current; (c) over-insulation, sometimes augmented by overcurrent; (d) localized heating due to strand breakage; (e) localized heating due to mechanical strand severing by staples or nails; and (f) localized heating due to failed terminations. Other failure modes are known but have received only limited study. These include (i) excessive force and creep; (ii) chemical interaction effects; and (iii) breakdown under voltage surge conditions. Additional research is needed in these areas. The proximate cause of ignition involved with many of the above mechanisms is arc tracking (arcing across a carbonized path). In turn, it is shown that PVC is especially susceptible to becoming charred, it requiring only approximately 1608C for the material to become semiconducting during shortterm exposure (around 10 h), while longer-term exposure (around 1 month) may cause failures at temperatures as low as 1108C. Some limited data exist which suggest that standard UL and IEC temperature classifications are unduly optimistic, as applied to PVC. Fire can originate if wiring or equipment cannot withstand a powerline surge. Mains-connected electrical appliances need to be designed to resist 6000 V surge voltages, even though this is not mandated in most of the current UL and IEC standards. Data are presented showing that the IEC 60112 wet-tracking test gives especially misleading results for PVC and should be improved or abrogated.

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“…A variety of different parameters such as the insulation resistance, polarization index, dissolved gas analysis (DGA), dissipation factor, winding temperature and partial discharge (PD) can be considered as indicators of transformer insulation conditions. Of these factors, PD measurement and DGA are frequently used in the assessment of transformer wellness [6]. In this research, these two parameters along with the insulation resistance have been measured periodically during the ageing process.…”

Section: Introductionmentioning

confidence: 99%

Effects of voltages with high-frequency contents on the transformer insulation properties

Khanali

Jayaram

Cheng³

2013

2013 IEEE Electrical Insulation Conference (EIC)

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This work studies the changes that occur in transformer insulation properties when voltages with steep fronts and high-frequency contents are applied. With a significant growth in the number of wind-farms and solar-plants that use power-electronic-based converters, the problems associated with such voltages on insulation has led to increasing concerns. Distorted voltages accelerate the transformer insulation degradation. Two identical transformers are studied by energizing independently under power frequency sinusoidal and width-modulated pulse trains. The dielectric characteristics of the test objects, like partial discharge activities, insulation resistance, are periodically measured during the ageing process. After a period of 500 hours of testing the dissolved gases are also analyzed. The results for both transformers are compared and discussed.

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Chapter 5 Polymer Degradation and Its Measurement

Cited by 6 publications

References 188 publications

The use of Electron Paramagnetic Resonance (EPR) in the probing of the nanodielectric interface

The use of Electron Paramagnetic Resonance (EPR) in the probing of the nanodielectric interface

Mechanisms and modes for ignition of low-voltage, PVC-insulated electrotechnical products

Effects of voltages with high-frequency contents on the transformer insulation properties

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