The ground connection of the generator is not shown in PTW but one can only enter the neutral impedance in the generator component. For the ground protection, the ground relay is added as another function in the phase relay in the circuit or added in series with the phase. However, if you need to visually display the connection in the drawings you may do so by using annotation lines as shown below. Keep in mind that the circuit are floating components and not electrically connected in the system in PTW.