Protection device for a vehicle for preventing contact voltages

A vehicle, comprising:

• an ungrounded vehicle frame;
• a traction drive supported by said ungrounded vehicle frame and selected from the group consisting of an electric traction drive and a hybrid-electric traction drive;
• a current collector being electrically connected to said traction drive and can be brought into galvanic contact with a contact line of a grounded contact line system to supply traction energy;
• and
• an electrical protection system for preventing dangerous contact voltages on said ungrounded vehicle frame or on a vehicle part conductively connected thereto, said electrical protection system having a second protection stage, being constituted by electrically single-insulated mounting at least of said traction drive on said ungrounded vehicle frame, and a first protection stage, being additionally constituted by an electrically isolating DC-DC converter which is connected between said current collector and said traction drive, said electrical protection system further having a switching element by means of which said electrical protection system can be switched between said first protection stage and said second protection stage through an optional connection in circuit or bypassing of said DC-DC converter, wherein said first protection stage providing a higher degree of safety from the dangerous contact voltages than said second protection stage, and said traction drive being supplied with the traction energy from the contact line in both said first and second protection stages.