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- Hammarström, Thomas, 1974, et al.
(författare)
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CHANGES IN PD PROPERTIES WITH DECREASING VOLTAGE RISE
- 2011
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Ingår i: The Proceedings of 17th International Symposium on High Voltage Engineering. - 9783800733644 ; , s. D-013
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Konferensbidrag (refereegranskat)abstract
- The increased use of power electronic components in power systems requiresunderstanding of how rapidly rising voltages affect insulation systems. One importantaspect of this challenge is to measure partial discharges, PDs, which are considered asbeing a sign of insulation weakness and can affect its life considerably. This paperpresents a continuation of our earlier investigations on the difference in PD behaviourwhen voltages characterized by different rise times are applied. The results indicate thatthe effect on the insulation system is indeed dependent on the voltage wave shape.Applying square-like voltages to a cavity with dielectric insulated electrodes significantlyaffects the discharge amplitude, its rise time, the inception voltage and the distributionshape. It is further examined how the dimensions of the cavity affect the PDcharacteristics and the investigation shows that PD amplitude increases while its durationdecreases for shorter voltage rise times, being indications of a possible change in thedischarge mechanism. This in turn can lead to faster deterioration and reduction ofinsulation service life. To illustrate the degradation process, microscopic images showhow shorter rise times affect differently the cavity surface deterioration, which isconsistent with the other observations.
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| 2. |
- Johansson, Anette, 1977, et al.
(författare)
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Wire-Plane Electrode System for Electrical Tree Initiation Exposed to AC and DC Voltage Stress
- 2011
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Ingår i: The Proceedings of 17th International Symposium on High Voltage Engineering, s. C-025. - 9783800733644
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Electrical treeing in XLPE exposed to DC (of both polarities) and 50 Hz AC voltages has been analysed in a wire-plane electrode geometry using real-time optical detection and microscopic observations. It has been found that treeing mechanisms differ between AC and DC stresses. For AC voltage, the tree initiation and growth is easily observable in real time during the testing. In the case of DC stress a complete breakdown of the XLPE occurs before electrical trees can be discerned with the use of CCD camera. However, in the microscopic observations of the specimens, very fine tree structures can be distinguished. The effect of voltage ramping rate was also analysed. For AC stress, the faster ramping results in a higher tree inception voltage. The opposite trend is true for DC stress, where the faster ramp results in a lower breakdown voltage level. When comparing the effect on polarity of the DC breakdown voltage, negative polarity results in higher voltage levels than positive polarity.
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| 3. |
- Ma, Bin, 1981, et al.
(författare)
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Performance of HTV Silicone Rubber under Artificial AC and DC Corona/Ozone Test
- 2011
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Ingår i: the Proceedings of 17th International Symposium on High Voltage Engineering. - 9783800733644 ; , s. E-036
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Konferensbidrag (refereegranskat)abstract
- This paper concentrates on presenting the changes of properties of high temperature vulcanized (HTV) silicone rubbers when exposed to 100 hours long corona/ozone treatment in a multi-needle electrode system, as suggested by CIGRE Working Group D1.14 and in detail reported in our former publication. The material samples were treated by either AC or DC corona sources. The HTV samples used in this test contained one type of a commercial HTV silicone rubber (including both post- and unpostcured specimens) based on polydimethylsiloxane (PDMS) as well as model HTV silicone rubbers containing increased amount of methylvinylsiloxane (MVS) and filled with aluminum-trihydrate (ATH) of different proportions. Material characterization methods involving volume and surface resistivity measurements, dielectric response (DR) measurement, as well as tensile tests were adopted to trace the performance changes of the samples induced by the AC or DC corona treatments.
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