In a regenerative braking emergency stop system, a substation includes: a rectifier transformer configured to transform AC power received from outside; a rectifier configured to convert the transformed AC power into DC power; and a switch disposed on an electrical path between the rectifier and a power-feed rail and configured to be in a closed state or an opened state; a simulated ripple transmitter configured to transmit a simulated ripple, the simulated ripple being an AC signal having a predetermined frequency; a superimposing circuit connected to the power-feed rail in parallel with the rectifier and configured to superimpose the simulated ripple transmitted from the simulated ripple transmitter on DC power outputted from the rectifier; and a relay device configured to allow the simulated ripple transmitter to transmit the simulated ripple when the rectifier is receiving power from outside and the switch is in a closed state.