HIGH-VOLTAGE ELECTRIC INSULATION BREAKS

I Type. FOR EXTERNAL VACUUM DISCHARGE GAPS.

The high-voltage electric insulation breaks for cryogenic communications are intended for various-purpose facilities cooled by helium at a temperature of 4.2-20Ê. They provide moderate resistance to helium flux and electrical insulation of communications which have electric potential difference.

II Type. FOR SOLID VACUUM DISCHARGE GAPS.

The high-voltage electric insulation break has an additional insulation layer with a conducting shield applied over it. The shield has the earth potential to preclude breakdown by the Pashen's curve in case of an abnormal deterioration in vacuum.

III Type. FOR PIPELINES OF "WARM" (ROOM TEMPERATURE) GASEOUS HELIUM.

Compact high-voltage electroinsulation breaks have been developed for cryogenic lines, which operate at temperature range of 300Ê - 4.2Ê. To enhance the electric strength of such breaks without increasing the geometric sizes the spiral channels with a low hydraulic pressure are used. 

Results of testing of the electroinsulation breaks :

Electric strength: 65 kV DC at t=20°Ñ (with helium inside the insulator)
Tightness: <10-9 mbar l/s at a pressure of 1 bar and 30 bar.
After 5 thermocycles from 300Ê to 77Ê and from 77Ê to 300Ê the tightness was:
<10-9 mbar l/s at a pressure of 1 bar and 30 bar.

Main technical characteristics

Coolant – helium at a temperature of 4.2-300 K I Type II Type III Type
HV break length (for the test samples), mm 160 360 275
Inner diameter (for the test samples), mm 9.7 12.7 20
Maximum operating voltage at a temperature of 4.2-20K, kV 15 15 32
Test voltage at a temperature of 4.2-15K, kV DC 30 31 65
Maximum operating pressure, MPa 2
Maximum test pressure, MPa 3
Maximum helium leak-in rate, mbar-l/sec 10-9
Helium leak less than, mbar-l/sec 10-9
Metal ends are made of 12X18H10T stainless steel