Accession Number : AD0013933

Title :   MOISTURE RESISTANCE AND DIELECTRIC BREAKDOWN OF ELECTRICAL INSULATING MATERIALS

Corporate Author : JOHNS HOPKINS UNIV BALTIMORE MD DIELECTRICS LAB

Personal Author(s) : CHAPMAN, JOHN J. ; FRISCO, LOUIS J.

Report Date : 15 MAY 1953

Pagination or Media Count : 7

Abstract : Polyethylene (I) and polytetrafluoroethylene (II) were negligibly affected by cycling at 60 c to 18 mc. The mica-filled PhOH-HCHO resin (III) was adversely affected by a high RH. The glass-silicone laminate (IV) had a low resistivity after a 15-min exposure to 100% RH. Deterioration was most significant at LF's and dc's than at RF's. The flashover value decreased with frequency of all the materials; III showed no drop in puncture strength even after exposure to high humidity for 90 days. II did not appear to absorb moisture under any conditions. I gained weight until it melted; III and IV lost weight. A Beechnut circuit was devised for measuring the dielectric constant and dissipation factor at 100 mc. A transformer was constructed for operation up to 45 kv. A cooling arrangement is described for -55 deg C puncture tests at 100 mc; final tuning is accomplished by adjusting the immersion liquid height. Varsol is used as the liquid insulant. Flow from the reservoir to the cell is provided by gravity. The adjustment of excess liquid also employs gravity for flow from the cell to the sump.

Descriptors :   , CELLS, CONSTANTS, COOLING, DETERIORATION, DIELECTRIC PROPERTIES, EXPOSURE(GENERAL), GRAVITY, HEIGHT, HIGH HUMIDITY, IMMERSION, LIQUIDS, MOISTURE, POLYETHYLENE, RESERVOIRS, RESISTANCE, TRANSFORMERS, TUNING.

Distribution Statement : APPROVED FOR PUBLIC RELEASE