ANSI C12.11

The ANSI protocol for instrument transformers for revenue metering—10 kV BIL (impulse insulation level) through 350 kV BIL. This standard covers general requirements for metering accuracy, thermal ratings, and transformer and inductively coupled transformer dimensions for revenue metering, 10 kV basic lightning BIL through 350 kV BIL for 0.6 kV nominal system voltage through 69 kV NSV.