The article presents the concept of the main circuit for a hybrid rail vehicle, improved with independent power storage, designed to transport various equipment for building, diagnosing and measuring of rail infrastructure. The vehicle is expected to have three independent drive systems, i.e. catenary line, batteries and emergency power generator. It can reach a speed of 160 km/h with catenary line power supply. In case of failure or shortage of catenary lines, the vehicle can use it's batteries. The batteries can be charged from catenary lines while driving or from a charging station when parked. The advantage of the vehicle is its zero-emission to the natural environment and the possibility to recover energy while braking. The energy is stored and used for propulsion to prolong its operation supported by power supplied from batteries. The power generator will only be used in an emergency, for short-distance driving at reduced speed. Modes of this vehicle operation were discussed, with particular emphasis on traction characteristics. All the energy flows in the main circuit under different operating conditions of the vehicle were analyzed and presented.