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Updated April 2017


​Main switch or breaker minimum interrupting capacity

Primary Services

Interrupting capacities for primary breakers and power fuses are:

    • 4.16 kV system: Capacity provided on request
    • 13.8 kV system: Up to 31,000 A (750 MVA)
    • 25 kV system: 12,000 A (500 MVA)
Conventional secondary services

For services connected to EDTI's Downtown Secondary Network, please see Table 9.

​Interrupting Capacity ​ ​ ​
​Main Switch or Breaker Size (AMPS) ​120/240 V 1-Phase, 3-Wire ​120/208 V 3-Phase, 4 Wire ​277/480 V 3-Phase, 4-Wire ​347/600 V 3-Phase, 4-Wire
​Up to 200 A ​10,000 ​25,000 ​22,000 ​14,000
​201-600 A 25,000​ ​42,000 ​30,000 ​22,000
​601-800 A ​- ​42,000 ​30,000 ​22,000
​801-1,200 A ​- ​65,000 ​50,000 ​25,000
​1,201-2,000 A ​- ​65,000 ​50,000 ​42,000
​2,001-3,000 A ​- ​85,000 ​60,000 ​48,000
  • All the current ratings specified in this table are root mean square (RMS) symmetrical values. The minimum interrupting capacity must apply to all components and to the assembly.
  • The interrupting capacities indicated are for one service from one matching transformer. When a larger transformer is installed to service several temporary or permanent main panels, the interrupting capacity must match the total capacity of all main services connected to the transformer. Contact EDTI Customer Engineering Services to confirm the requirements.
  • For temporary services supplied from a permanent transformer, interrupting ratings must match the available fault currents at the transformer. Confirm the rating with an EDTI Customer Engineering Services representative.