it uses what they call a TWACS system. there's a big pad mount sitting in the substation that shorts out every so often through some big resistors that puts a pulse on the line that reads the meter.as they say so far so good.
TWACS system was tried here in NZ with an American injection system used via a 11 kV / 277 / 480 Volts special transformer in a semie rural substation.( 33kV / 11 kV ). The results were dissapointing as what I heard of it and the overall costs to high to warrant the investment in putting all the extra plant in and upgrade all the kWh meters at the same time.
It was also planned to use TWACS for auto dis - re connect brakers on awkward customers to remotely switch them off or on for non payment.
I'm not sure if the design was specified for 50 Hz which we use here because a lot was done a little bit in a secret way with locked control boxes.
I was involved in getting the 11 kV supply to the TWACS transformer.
