• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1998.06a
• /
• pp.19-23
• /
• 1998

Water tree degradations have been considered as one of the most important causes of failure in underground distribution cables with polymeric insulation. Water tree growth is a preliminary step in the sequence of electrical tree initiation and electrical breakdown of the insulation. In this paper, needle electrode is made use of the etching methods and the pellet type specimen is made to observe the water tree in succession. In previous methods are able to observe the tree degradations without cutting and dyeing. The water tree image is recorded on VTR with CCD camera. The tree length of X, Y axis direction and aging area(treeing area) are calculated with image measurement. As a result of this study, water tree is observed by non-destructive method. Electrical tree is initiated from needle electrode tip only but water tree is initiated from total area of water electrode. Electrical tree owing to water treeing is initiated at low electric field and grown with discontinuously. Namely, water tree is shown up a different characteristics of tree growth.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.13 no.12
• /
• pp.1063-1068
• /
• 2000

Water treeing in underground distribution power cable is not easy to observe by nondestructive method and it has very complex patterns. This study describes the principles and practices of a continuous observation of initiation and growth of tree in polymeric insulation material using an image measurement technique. Using this technique we could observe water tree and the growing process of electrical tree due to the water tree and the growing process of electrical tree due to the water tree. All of these growing process is analyzed quantitatively by image measurement program composed of borland c++. We fabricated the thin film type specimen to observe water tree easier and also the needle electrode was prepared by etching method using electrolytes. Initiation and the growth of three was observed somewhat different depending on the applied voltage and the water electrode. AgNO$_3$solution electrode accelerates the initiation and the growth of water tree, compared to those of distilled water electrode. The water and the electrical tree occurred by water tree has discontinuous growth characteristic.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1997.11a
• /
• pp.409-412
• /
• 1997

The phenomenon of water tree degradation of underground distribution power cables is taking place in polymeric insulation materials under the existence of water and application of electric stress, but water tree is not easy to observe, o water tree features in power cables are shown after cutting and dying with methyleneblue. In previous method, it is impossible to acquire continuous treeing data, and when the insulation material has been cut, the micro crack(water tree) has been damaged. In this paper, to overcome these deflects, the etching method is made use of making needle electrode about 170[${\mu}{\textrm}{m}$] diameter, and AgNO$_3$(silver nitrate) solution is used as liquid electrode to accelerate the growth of water trees. As a result of this study, water tree is observed in real-time with microscope. Electrical tree owing to water treeing is initiated at low electric field and grown with discontinuous. Namely, water tree is shown up a different characteristics of tree growth.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1998.06a
• /
• pp.219-222
• /
• 1998

In this study, The water tree characteristics were investigated when crosslinking coagent was added in XLPE/EnBA blends. When XLPE was blended with EnBA, there was a decrease of water tree length as an increase of nBA contents in XLPE/EnBA20 blends. The effect of crosslinking coagent. A was better than those of other crosslinking coagents B, C and D in water tree retardation. In case of XLPE/EnBA/Crosslinking coagent blends, water tree length was increased as the crosslinking coagents were increased from 0.2 to 2 phr in 2.0 phr DCP content. To clarify the effects of crosslinking coagent, the DCP contents were changed from 1.5 to 2.0 par in the same crosslinking coagent contents. Then, there was a decrease of water tree length as an increase of crosslinking coagent contents in 1.5 and 1.8 phr DCP contents.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.34 no.11
• /
• pp.436-439
• /
• 1985

An effect of the salt solution on the Water Tree Propagation was shown systematically from the actions of the salt concentration in deionized water. It may be able to suggest that the tree propagation is possibly to be connected with an intervention of the electrochemical or chemical actions of the salt solution on water tree propagation, which may likely depend on the growth level of the trees. We have pointed out that it is necessary to study the structure of water tree under the electrical stress.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1997.04a
• /
• pp.346-349
• /
• 1997

It is well known that water treeing is one of the main cause of breakdown in underground power cables, but water tree is not easy to observe. This aging phenomenon was resulted in effect of water and electric field and so on. In this paper, Distilled water was used as water electrode to observe the water treeing in XLPE(cross-linked polyethylene). To observe easily, sample was made of pallet types so water tree was able to show by microscope. As a result, electrical tree appears at niddle electrode tip which was concentrated electric field, but water tree was shown up different types that were appealed in total area of water electrode as well as water electrode tip.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.13 no.5
• /
• pp.420-425
• /
• 2000

Crosslinked polyethlyene/silane crosslinked polyethylene(XLPE/SXLPE) blends were prepared by a twin screw extruder and their water tree growing electrical breakdown and crossinking characteristics were investigated. The water tree characteristics of XLPE were improved by the addition of SXLPE when samples were crosslinked only by the thermorolysis of DCP (dicumyl peroxide). However steam curing process was not good for water tree characteristics. It was also found that the rate of water tree growing of XLPE/SXLPE blend increased when the content of SXLPE was 50%. AC breadown strength slightly increaed by the addition of SXLPE to XLPE when samples were crosslinked only by the thermorolysis of DCP. It was also found that the degree of crosslinking of XLPE/SXLPE blends were higher than that of XLPE in the case of the content without steam crosslinking process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.295-295
• /
• 2008

Water tree experiments were done for several types of cross-linked polyethylenes. Test method is followed by ASTM D6097. Polyethylene is divided for four subgroup. First One is chemically cross-linked general XLPE, and second one is chemically cross-linked tree-retardant XLPE, and the third one is silane cross-linked polyethylene made by monosil process, and the last one is silane cross-linked polythylene made by copolymer. Tree retardant XLPE shows the shortest water tree length. Cahemcally cross-linked general XLPE shows the longest water tree length. Silane cross-linked polyethylene by copolymer is similar to tree retardant XLPE and similar breakdown strength. So silane cross-linked XLPE by copolymer could be used for the the medium voltage cable which should have tree retardant characteristics.

• Korean Journal of Agricultural Science
• /
• v.50 no.4
• /
• pp.883-902
• /
• 2023

Water is critical to the health and productivity of fruit trees. Efficient monitoring of water stress is essential for optimizing irrigation practices and ensuring sustainable fruit production. Short-range sensing can be reliable, rapid, inexpensive, and used for applications based on well-developed and validated algorithms. This paper reviews the recent advancement in fruit tree water stress detection via short-range sensing, which can be used for irrigation scheduling in orchards. Thermal imagery, near-infrared, and shortwave infrared methods are widely used for crop water stress detection. This review also presents research demonstrating the efficacy of short-range sensing in detecting water stress indicators in different fruit tree species. These indicators include changes in leaf temperature, stomatal conductance, chlorophyll content, and canopy reflectance. Short-range sensing enables precision irrigation strategies by utilizing real-time data to customize water applications for individual fruit trees or specific orchard areas. This approach leads to benefits, such as water conservation, optimized resource utilization, and improved fruit quality and yield. Short-range sensing shows great promise for potentially changing water stress monitoring in fruit trees. It could become a useful tool for effective fruit tree water stress management through continued research and development.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.11a
• /
• pp.55-58
• /
• 1999

Crosslinked polyethylene/silane crosslinked polyethylene (XLPE/SXLPE) blends were prepared by a twin screw extruder and their water tree growing and electrical breakdown characteristics of XLPE were improved by the addition of SXLPE, when samples were crosslinked only by the thermorolysis of DCP (dicumyl perosxide). However, steam curing process was not good for water tree characteristics. It was also found that the rate of water tree growing of XLPE/SXLPE blend increased when the content of SXLPE was 50 %. AC breadown strength slightly increased by the addition of SXLPE to XLPE when samples were crosslinked only by the thermorolysis of DCP.