Integrated energy system is an important trend of power and energy industry, but its basic theories still need to be further studied. The calculation of energy utilization efficiency should be based on the second law of thermodynamics and the relevant national standard is being formed. The characteristics of transfers of energy and exergy through pipelines play an important role in the plan, design and optimization of integrated energy system. The mathematical expressions of variations of electric, thermal and pressure energies and exergies along pipelines are derived from the generalized expressions of transfer and conversion equations of energy and exergy. These expressions show that the losses of energy and exergy are related with the geometrical dimensions and the material qualities of the pipelines. These dimension and quality determine the investment of the equipment, and these expressions show that the greater the investment, the smaller the losses of the energy and exergy. So the research presented in this paper will provide a theoretical foundation for optimization of integrated energy systems.