A transformer fault detection, where the transformer includes a primary winding coupled to a medium voltage power line and a secondary winding providing a stepped down voltage of the medium voltage. The detection system includes a switching device, where the switching device includes a first voltage measuring device for measuring the voltage on the primary winding, a controller for processing measured voltages and a transceiver for receiving and transmitting messages. The detection system also includes a second voltage measuring device for measuring the stepped down voltage on the secondary winding, where the second voltage measuring device includes a transmitter for transmitting the measured step down voltage to the switching device. The controller uses the measured voltages to calculate a transformer turns ratio (TTR) of the transformer to determine whether a transformer fault.