SMITH_USA_Author_ALPHA1_BLOCK1_Question 1-6 Barcelona May Question 1-6 Are There Fundamental Performance Limits for Vacuum Breaking Technology? R. Kirkland Smith, Ph.D. Eaton / Cutler-Hammer, Horseheads, NY, USA

SMITH_USA_Author_ALPHA1_BLOCK1_Question 1-6 Barcelona May Key Vacuum Interrupter Functions Carry continuous current Carry peak momentary current Interrupt fault currents Withstand high voltages

SMITH_USA_Author_ALPHA1_BLOCK1_Question 1-6 Barcelona May Carry continuous current Vacuum interrupters have one pair of contacts All heat must be conducted through the terminals 3150 Amps is typical convection cooled rating 4000 and maybe 5000 amps - forced cooled Cooling is a limit

SMITH_USA_Author_ALPHA1_BLOCK1_Question 1-6 Barcelona May Carry peak momentary current Vacuum interrupters have one pair of contacts Added force must counter blow-off force at 25 kA kilograms force required at 100 kA kilograms force required High mechanism force is a limit

SMITH_USA_Author_ALPHA1_BLOCK1_Question 1-6 Barcelona May Interrupt fault currents VIs now available at –63 and 80 kA at 15 kV –40 kA at 38 kV Fault interruptions to 200 kA reported Experimental units work at 72.5 kV - 63 kA Interruption ratings meet most needs

SMITH_USA_Author_ALPHA1_BLOCK1_Question 1-6 Barcelona May Withstand high voltages Breakdown voltage of vacuum gap levels off as gap increases kV peak is practical limit 72.5 kV in a one VI looks like a limit Withstand voltage is a definite limit

SMITH_USA_Author_ALPHA1_BLOCK1_Question 1-6 Barcelona May Probable Future VI Ratings Low Voltage to 1.5 kV –100 to 200 kA 3150 to 4000 / 5000 A Medium Voltage to 52 kV –63 to 80 kA 3150 to 4000 / 5000 A High Voltage to 72.5 kV / 84 kV –40 to 80 kAup to 3150 A –Two VIs in series will do 145 kV