1. SMITH_USA_Author_ALPHA1_BLOCK1_Question 1-6 Barcelona 12-15 May 2003 1 Question 1-6 Are There Fundamental Performance Limits for Vacuum Breaking Technology? R. Kirkland Smith, Ph.D. Eaton / Cutler-Hammer, Horseheads, NY, USA

2. SMITH_USA_Author_ALPHA1_BLOCK1_Question 1-6 Barcelona 12-15 May 2003 2 Key Vacuum Interrupter Functions Carry continuous current Carry peak momentary current Interrupt fault currents Withstand high voltages

3. SMITH_USA_Author_ALPHA1_BLOCK1_Question 1-6 Barcelona 12-15 May 2003 3 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

4. SMITH_USA_Author_ALPHA1_BLOCK1_Question 1-6 Barcelona 12-15 May 2003 4 Carry peak momentary current Vacuum interrupters have one pair of contacts Added force must counter blow-off force at 25 kA - 200 kilograms force required at 100 kA - 1700 kilograms force required High mechanism force is a limit

5. SMITH_USA_Author_ALPHA1_BLOCK1_Question 1-6 Barcelona 12-15 May 2003 5 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

6. SMITH_USA_Author_ALPHA1_BLOCK1_Question 1-6 Barcelona 12-15 May 2003 6 Withstand high voltages Breakdown voltage of vacuum gap levels off as gap increases 400 - 600 kV peak is practical limit 72.5 kV in a one VI looks like a limit Withstand voltage is a definite limit

7. SMITH_USA_Author_ALPHA1_BLOCK1_Question 1-6 Barcelona 12-15 May 2003 7 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