At the front of the plug are connectors linked via 1M Ohm resistors to the earth pin, inside the plug. The connectors offer a link to ground for connecting cords from the EPA.
The1M Ohm resistor to each connector offer protection in the event the workstation becomes live. That protection would limit the current to less than 0.3mA at 240 volts. Should the fault current continue the resistor will open circuit.