The Experts below are selected from a list of 189 Experts worldwide ranked by ideXlab platform
S. Hvidsten - One of the best experts on this subject based on the ideXlab platform.
-
Effect of test voltage frequency on PD inception in Service aged cable joints
2014 ICHVE International Conference on High Voltage Engineering and Application, 2014Co-Authors: Frank Mauseth, H. Tollefsen, S. HvidstenAbstract:Condition assessment of cable systems can today be performed at different voltage frequencies. This includes VLF testing at 0.1 Hz, 50 Hz (also on-line) and also at higher frequencies in the range of 200–500 Hz by using oscillating wave test techniques. An important parameter used during condition assessment is the inception voltage of partial discharges. If this voltage is well above the Service Stress the cable system is likely not aged by partial discharges during Service. The underlying assumption during testing is that this voltage is independent of frequency.
-
Effect of test voltage frequency on PD inception in Service aged cable joints
2014 ICHVE International Conference on High Voltage Engineering and Application, 2014Co-Authors: Frank Mauseth, H. Tollefsen, S. HvidstenAbstract:Condition assessment of cable systems can today be performed at different voltage frequencies. This includes VLF testing at 0.1 Hz, 50 Hz (also on-line) and also at higher frequencies in the range of 200-500 Hz by using oscillating wave test techniques. An important parameter used during condition assessment is the inception voltage of partial discharges. If this voltage is well above the Service Stress the cable system is likely not aged by partial discharges during Service. The underlying assumption during testing is that this voltage is independent of frequency. The main purpose of this study has been to measure the inception voltage and characteristics of partial discharges in Service-aged XLPE cold-shrink cable joints. A set-up with possibilities to measure partial discharges in a broad frequency range from 1 mHz to 100 Hz with a voltage up to 20 kV was used. Especial attention has been paid to the frequency dependency of the magnitude and number of the discharges. The results show that the inception voltage can be frequency dependent. It is therefore important to take this into consideration when assessing the condition of cable systems.
-
Condition assessment of 12- and 24-kV XLPE cables installed during the 80s. Results from a joint Norwegian/Swedish research project
IEEE Electrical Insulation Magazine, 2005Co-Authors: S. Hvidsten, B. Holmgren, L. Adeen, J. WetterstromAbstract:This paper reports the results from the condition assessment of 12- and 24-kV cross-linked polyethylene (XPLE) cables using a technique based on dielectric spectroscopy initially developed at KTH in Sweden. The work aims to examine whether the method could detect water tree degradation for the second generation medium voltage (MV) cables with long, but not bridging, water trees. While the overall cable condition was better than expected for second generation XPLE cables, water trees were found in most of the selected cables. The diagnostic method based on the measurement of the dielectric response could only detect water tree degradation in the examined second generation cables when the water trees bridged the insulation wall. Condition assessment above Service Stress may, in some cases, be required to detect bridging water trees. The results indicate that there is a correlation between the voltage level and the breakdown voltage of the cable. This can be used as a diagnostic criterion for this group of cables.
Arve Ryen - One of the best experts on this subject based on the ideXlab platform.
-
Initiation of vented water trees from the conductor screen of MV XLPE insulated cables
2012 IEEE International Symposium on Electrical Insulation, 2012Co-Authors: Hallvard Faremo, Mildrid Selsjord, Sverre Hvidsten, Karl Magnus Bengtsson, Arve RyenAbstract:It has previously been shown for Service aged XLPE cables that porous structures in the conductor screen do develop and serve as paths for contaminants and corrosion products from the aluminum conductor initiating vented water trees. It was found that a prerequisite for the formation of such structures is the presence of liquid water at the interface between the conductor and conductor screen causing corrosion. The main objective with this work is to reproduce this phenomenon in the laboratory and to examine if porous zones can develop even without Service Stress (voltage/current). 12 kV XLPE cables with Al conductor were subjected to 40°C and 3U0 in water. The effect of mechanical and electrical Stress, and filling between the conductor strands on the formation of the porous zones initiating vented water trees were examined. It is shown that the phenomenon observed for Service aged cables is reproduced in the laboratory, and that e.g. the formation of interconnected porous structures in the conductor screen is independent of the applied voltage and load current. The structures are also strongly correlated to corrosion sites at the Al conductor surfaces. No such zones were observed for the cables with swelling powder.
-
Initiation of vented water trees from the conductor screen of MV XLPE insulated cables
2012 IEEE International Symposium on Electrical Insulation, 2012Co-Authors: Hallvard Faremo, Mildrid Selsjord, Sverre Hvidsten, Karl Magnus Bengtsson, Arve RyenAbstract:It has previously been shown for Service aged XLPE cables that porous structures in the conductor screen do develop and serve as paths for contaminants and corrosion products from the aluminum conductor initiating vented water trees. It was found that a prerequisite for the formation of such structures is the presence of liquid water at the interface between the conductor and conductor screen causing corrosion. The main objective with this work is to reproduce this phenomenon in the laboratory and to examine if porous zones can develop even without Service Stress (voltage/current).
Frank Mauseth - One of the best experts on this subject based on the ideXlab platform.
-
Effect of test voltage frequency on PD inception in Service aged cable joints
2014 ICHVE International Conference on High Voltage Engineering and Application, 2014Co-Authors: Frank Mauseth, H. Tollefsen, S. HvidstenAbstract:Condition assessment of cable systems can today be performed at different voltage frequencies. This includes VLF testing at 0.1 Hz, 50 Hz (also on-line) and also at higher frequencies in the range of 200–500 Hz by using oscillating wave test techniques. An important parameter used during condition assessment is the inception voltage of partial discharges. If this voltage is well above the Service Stress the cable system is likely not aged by partial discharges during Service. The underlying assumption during testing is that this voltage is independent of frequency.
-
Effect of test voltage frequency on PD inception in Service aged cable joints
2014 ICHVE International Conference on High Voltage Engineering and Application, 2014Co-Authors: Frank Mauseth, H. Tollefsen, S. HvidstenAbstract:Condition assessment of cable systems can today be performed at different voltage frequencies. This includes VLF testing at 0.1 Hz, 50 Hz (also on-line) and also at higher frequencies in the range of 200-500 Hz by using oscillating wave test techniques. An important parameter used during condition assessment is the inception voltage of partial discharges. If this voltage is well above the Service Stress the cable system is likely not aged by partial discharges during Service. The underlying assumption during testing is that this voltage is independent of frequency. The main purpose of this study has been to measure the inception voltage and characteristics of partial discharges in Service-aged XLPE cold-shrink cable joints. A set-up with possibilities to measure partial discharges in a broad frequency range from 1 mHz to 100 Hz with a voltage up to 20 kV was used. Especial attention has been paid to the frequency dependency of the magnitude and number of the discharges. The results show that the inception voltage can be frequency dependent. It is therefore important to take this into consideration when assessing the condition of cable systems.
-
Surface degradation of XLPE insulation at oil-water interfaces
2011 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, 2011Co-Authors: Frank Mauseth, Sverre Hvidsten, Geir BirkenesAbstract:Water ingress in high voltage oil-filled XLPE cable terminations has been found to be one of the main reasons for Service breakdown causing a high risk of life for nearby personnel due to a possible explosion of the component. Some utilities perform regularly maintenance of such installations by measurements of water content of the oils. It was found that for some installations the water content was high, where even liquid water was present in the oil [1]. The breakdown mechanism for such situations is yet not clear. The main purpose of this work has therefore been to examine the effect of liquid water in the oil in such installations. The work has been performed on small scale model terminations. A small glass container was filled with oil having water at the bottom. The AC voltage was increased to 4.4 kV/mm in steps of 0.7 kV/mm with 30 minutes at each step. Subsequent measurements of partial discharge and video recording were done at each step. Long-term tests were also performed on six similar set-ups. The results show that partial discharges can only occur with the water layer grounded. It is also observed that a thin irregular water film is growing more than 10 mm along the cable surface in the oil up to about half the Service Stress (1.6 kV/mm) and stop growing further. The partial discharges, varying from 5 to 75 pC, are closely related to the release of water droplets from the irregular water film at higher Stresses. Long-term tests resulted in water induced breakdown for one of the set-ups.
Sverre Hvidsten - One of the best experts on this subject based on the ideXlab platform.
-
Initiation of vented water trees from the conductor screen of MV XLPE insulated cables
2012 IEEE International Symposium on Electrical Insulation, 2012Co-Authors: Hallvard Faremo, Mildrid Selsjord, Sverre Hvidsten, Karl Magnus Bengtsson, Arve RyenAbstract:It has previously been shown for Service aged XLPE cables that porous structures in the conductor screen do develop and serve as paths for contaminants and corrosion products from the aluminum conductor initiating vented water trees. It was found that a prerequisite for the formation of such structures is the presence of liquid water at the interface between the conductor and conductor screen causing corrosion. The main objective with this work is to reproduce this phenomenon in the laboratory and to examine if porous zones can develop even without Service Stress (voltage/current). 12 kV XLPE cables with Al conductor were subjected to 40°C and 3U0 in water. The effect of mechanical and electrical Stress, and filling between the conductor strands on the formation of the porous zones initiating vented water trees were examined. It is shown that the phenomenon observed for Service aged cables is reproduced in the laboratory, and that e.g. the formation of interconnected porous structures in the conductor screen is independent of the applied voltage and load current. The structures are also strongly correlated to corrosion sites at the Al conductor surfaces. No such zones were observed for the cables with swelling powder.
-
Initiation of vented water trees from the conductor screen of MV XLPE insulated cables
2012 IEEE International Symposium on Electrical Insulation, 2012Co-Authors: Hallvard Faremo, Mildrid Selsjord, Sverre Hvidsten, Karl Magnus Bengtsson, Arve RyenAbstract:It has previously been shown for Service aged XLPE cables that porous structures in the conductor screen do develop and serve as paths for contaminants and corrosion products from the aluminum conductor initiating vented water trees. It was found that a prerequisite for the formation of such structures is the presence of liquid water at the interface between the conductor and conductor screen causing corrosion. The main objective with this work is to reproduce this phenomenon in the laboratory and to examine if porous zones can develop even without Service Stress (voltage/current).
-
Surface degradation of XLPE insulation at oil-water interfaces
2011 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, 2011Co-Authors: Frank Mauseth, Sverre Hvidsten, Geir BirkenesAbstract:Water ingress in high voltage oil-filled XLPE cable terminations has been found to be one of the main reasons for Service breakdown causing a high risk of life for nearby personnel due to a possible explosion of the component. Some utilities perform regularly maintenance of such installations by measurements of water content of the oils. It was found that for some installations the water content was high, where even liquid water was present in the oil [1]. The breakdown mechanism for such situations is yet not clear. The main purpose of this work has therefore been to examine the effect of liquid water in the oil in such installations. The work has been performed on small scale model terminations. A small glass container was filled with oil having water at the bottom. The AC voltage was increased to 4.4 kV/mm in steps of 0.7 kV/mm with 30 minutes at each step. Subsequent measurements of partial discharge and video recording were done at each step. Long-term tests were also performed on six similar set-ups. The results show that partial discharges can only occur with the water layer grounded. It is also observed that a thin irregular water film is growing more than 10 mm along the cable surface in the oil up to about half the Service Stress (1.6 kV/mm) and stop growing further. The partial discharges, varying from 5 to 75 pC, are closely related to the release of water droplets from the irregular water film at higher Stresses. Long-term tests resulted in water induced breakdown for one of the set-ups.
Hallvard Faremo - One of the best experts on this subject based on the ideXlab platform.
-
Initiation of vented water trees from the conductor screen of MV XLPE insulated cables
2012 IEEE International Symposium on Electrical Insulation, 2012Co-Authors: Hallvard Faremo, Mildrid Selsjord, Sverre Hvidsten, Karl Magnus Bengtsson, Arve RyenAbstract:It has previously been shown for Service aged XLPE cables that porous structures in the conductor screen do develop and serve as paths for contaminants and corrosion products from the aluminum conductor initiating vented water trees. It was found that a prerequisite for the formation of such structures is the presence of liquid water at the interface between the conductor and conductor screen causing corrosion. The main objective with this work is to reproduce this phenomenon in the laboratory and to examine if porous zones can develop even without Service Stress (voltage/current). 12 kV XLPE cables with Al conductor were subjected to 40°C and 3U0 in water. The effect of mechanical and electrical Stress, and filling between the conductor strands on the formation of the porous zones initiating vented water trees were examined. It is shown that the phenomenon observed for Service aged cables is reproduced in the laboratory, and that e.g. the formation of interconnected porous structures in the conductor screen is independent of the applied voltage and load current. The structures are also strongly correlated to corrosion sites at the Al conductor surfaces. No such zones were observed for the cables with swelling powder.
-
Initiation of vented water trees from the conductor screen of MV XLPE insulated cables
2012 IEEE International Symposium on Electrical Insulation, 2012Co-Authors: Hallvard Faremo, Mildrid Selsjord, Sverre Hvidsten, Karl Magnus Bengtsson, Arve RyenAbstract:It has previously been shown for Service aged XLPE cables that porous structures in the conductor screen do develop and serve as paths for contaminants and corrosion products from the aluminum conductor initiating vented water trees. It was found that a prerequisite for the formation of such structures is the presence of liquid water at the interface between the conductor and conductor screen causing corrosion. The main objective with this work is to reproduce this phenomenon in the laboratory and to examine if porous zones can develop even without Service Stress (voltage/current).