1997 Fiscal Year Final Research Report Summary
Evaluation of Electrical Characteristics of Polymer/Liquid Nitrogen Composite Insulation System in Liquid Nitrogen Flowing
| Project/Area Number |
08650378
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | Nagoya Institute of Technology |
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Principal Investigator |
MIZUNO Yukio Nagoya Institute of Technology, Faculty of Engineering, (Department of Electrical & Computer Engineering), Associate professor, 工学部, 助教授 (50190658)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Liquid nitrogen / Polymer / Flowing / Breakdown voltage / Flashover voltage / Partial discharge / Lifetime |
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| Research Abstract |
The effect of liquid nitrogen flowing on electrical characteristics of cryogenic insulation systems was studied. Breakdown voltage, surface flashover voltage along polymeric rods, life time to breakdown of polymeric film (s) subjected to partial discharges, were investigated in artificially flowing liquid nitrogen comparing with those in naturally circulating liquid nitrogen by heat inflow.
The main results obtained are as follows :
1. Breakdown voltage of flowing liquid nitrogen increased slightly compared with that in liquid nitrogen naturally circulated by heat inflow to the chamber.
2. Surface flashover voltage along acrylic rods increased gradually with increasing flow rate of liquid nitrogen.
3. Liquid nitrogen flowing resulted in longer lifetime to breakdown of a polyethylene film caused by partial discharges in liquid nitrogen.
4. Partial discharge inception and extinction voltages are higher in flowing liquid nitrogen.
5. Partial discharge measurement in the life tests showed that cumulative charge and cumulative number of discharge are smaller in flowing liquid nitrogen.
6. Continuous partial discharge activity was observed in liquid nitrogen naturally circulated by heat inflow. In flowing liquid nitrogen, however, partial discharge sometimes stopped.
7. In the case of two-layred polyethylene films, similar phenomena were observed.
It is considered that flowing of liquid nitrogen may blast discharge. Restraint of inception and/or propagation of discharges by liquid nitrogen flowing may improve electrical characteristics.
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