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Title: Non-Uniform Field Breakdown and Surface Flashover in Liquid Nitrogen Gaps for HTS Applications

Abstract

Abstract: Liquid nitrogen (LN2) is used as a coolant and electrical insulation in many High Temperature Superconducting (HTS) applications. Hence a good understanding of the breakdown characteristics of this medium under a variety of practical electrode geometries and conditions is needed for design of high voltage equipment. While there is considerable literature on breakdown of LN2 gaps for uniform (plane-plane) or quasi-uniform electric fields (sphere-plane), there is much less data available for highly non-uniform field gaps and for surface flashover along insulators. In this paper we present results on sphere-plane and cylindrical rod-plane gaps in LN2 as a function of sphere and rod diameters and radius of the rod edge at 1 bar pressure. In addition the surface flashover voltages of Fiber-Reinforced Plastic (FRP) in LN2 with these electrode arrangements will also be reported.

Authors:
 [1];  [1];  [1];  [1];  [2];  [3]
  1. ORNL
  2. Consultant, SuperPower, Inc.
  3. SuperPower Incorporated, Schenectady, New York
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
OE USDOE - Office of Electric Transmission and Distribution
OSTI Identifier:
931691
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: 2006 IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), Kansas City, MO, USA, 20061015, 20061018
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BREAKDOWN; COOLANTS; DESIGN; DIELECTRIC MATERIALS; ELECTRIC FIELDS; ELECTRICAL INSULATION; ELECTRODES; FLASHOVER; NITROGEN; PLASTICS; cryogenic dielectrics; surface flashover; breakdown voltage; liquid nitrogen; fiberglass reinforced plastic

Citation Formats

James, David Randy, Sauers, Isidor, Tuncer, Enis, Ellis, Alvin R, Tekletsadik, Kasegn, and Hazelton, Drew. Non-Uniform Field Breakdown and Surface Flashover in Liquid Nitrogen Gaps for HTS Applications. United States: N. p., 2006. Web.
James, David Randy, Sauers, Isidor, Tuncer, Enis, Ellis, Alvin R, Tekletsadik, Kasegn, & Hazelton, Drew. Non-Uniform Field Breakdown and Surface Flashover in Liquid Nitrogen Gaps for HTS Applications. United States.
James, David Randy, Sauers, Isidor, Tuncer, Enis, Ellis, Alvin R, Tekletsadik, Kasegn, and Hazelton, Drew. Sun . "Non-Uniform Field Breakdown and Surface Flashover in Liquid Nitrogen Gaps for HTS Applications". United States. doi:.
@article{osti_931691,
title = {Non-Uniform Field Breakdown and Surface Flashover in Liquid Nitrogen Gaps for HTS Applications},
author = {James, David Randy and Sauers, Isidor and Tuncer, Enis and Ellis, Alvin R and Tekletsadik, Kasegn and Hazelton, Drew},
abstractNote = {Abstract: Liquid nitrogen (LN2) is used as a coolant and electrical insulation in many High Temperature Superconducting (HTS) applications. Hence a good understanding of the breakdown characteristics of this medium under a variety of practical electrode geometries and conditions is needed for design of high voltage equipment. While there is considerable literature on breakdown of LN2 gaps for uniform (plane-plane) or quasi-uniform electric fields (sphere-plane), there is much less data available for highly non-uniform field gaps and for surface flashover along insulators. In this paper we present results on sphere-plane and cylindrical rod-plane gaps in LN2 as a function of sphere and rod diameters and radius of the rod edge at 1 bar pressure. In addition the surface flashover voltages of Fiber-Reinforced Plastic (FRP) in LN2 with these electrode arrangements will also be reported.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}

Conference:
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  • Liquid nitrogen (LN2) is commonly used both as a coolant and electrical insulation in high temperature superconductor (HTS) equipment for power applications. Hence it is necessary to know the electrical breakdown characteristics of LN2 under a variety of conditions which are likely to be encountered in practice. The ac breakdown and positive and negative polarity breakdown results for lightning impulse (1.2 microsecond rise time/50 microsecond fall time) are presented for LN2 using sphere to plane electrode geometry for sphere diameters of 50.8 and 101.6 mm over a gap range of 1 to 15 mm. Voltages up to 110 kVrms weremore » studied for ac breakdown and up to 500-kV peak for impulse. In this work both the ac and impulse breakdown voltages scale approximately with distance over the limited gaps studied which is indicative of a quasi-uniform (near- uniform) electric field between sphere and plane. These measurements were conducted in a dewar which could be pressurized from 1 to 2 bar absolute which greatly reduces the spontaneous formation of bubbles that can occur in open LN2 bath experiments and thus potentially reduce the breakdown strength. Results from the pressurized system and near atmospheric pressure similar to an open bath are compared.« less
  • For high temperature superconducting (HTS) power applications it is necessary to improve the understanding of the dielectric properties of materials in a cryogenic environment. It is necessary to know the breakdown strength of materials and systems as a function of gap in order to scale to higher voltages. The partial discharge (PD) onset voltage for materials is also very important since the primary aging mechanism at cryogenic temperature is PD. Another important design characteristic is the surface flashover voltage of a material in liquid nitrogen as a function of gap. With these characteristics in mind, several generic materials were investigatedmore » under a variety of electrode and gap configurations. The impulse breakdown voltage and PD onset of three types of commercial polyetherimide, filled and unfilled, were measured at room temperature and 77 K. A modest increase in PD onset voltage was observed at the lower temperature. Breakdown voltages of fiberglass reinforced plastic (FRP) cylinders for two wall thicknesses were measured which showed a decrease in strength at the larger gap. Breakdown voltages for liquid nitrogen using a sphere-plane electrode geometry were measured. Also flashover voltages along a FRP plate immersed in liquid nitrogen were performed for sphere-plane and rod-plane electrodes at 1 bar pressure. It was found that the breakdown voltage increased only slightly with increasing gap lengths.« less
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