isxModularPduDeviceNominalMainInputVoltage 1.3.6.1.4.1.318.1.1.23.2.4

The nominal main input voltage to the system. Measured in Volts, line-to-line for a 3-wire (delta) service or line-to-neutral for a 4-wire (wye) service. -1 if main input voltage is not being measured.