Voltage simulation

Dear all,
I mean to simulate voltage effects in Gromacs similar to what happens in electrospinning by voltage.
Upon electrospinning we used 15 kV voltage. But, I do not know how much voltage (e.g. electric-field-z = 1 0 0 0) is needed in Gromacs to be similar to what we did.
Could you please help me with this?

Many thanks,