How to simulate the cable couple?

Hi, I have a problem about he cable couple. It is :
When the cable is located the transient electric field and illuminate by the field, there is an couducted voltage between the shielding metal and the core of the cable. The shielding metal can be grounded or not. I want to know, how to simulate the ground in the FDTD or MOM software? I simulate the model in the CST, but the voltage is ZERO.
Wounld you help me ?
Thank you!