This is in violation of electrical code unless you have run a separate ground wire back to your main electrical box and connected it to the proper ground.
Ground wire terminations are usually in the breaker box. The breaker box is then grounded to a copper or copper clad 8 foot stake driven into the earth. But this can vary depending on local codes, as some areas have difficulty in obtaining good grounds. (dry sandy soil for instance)
Good Luck!
Dodgeman