Knowledge of air-water vapor mixtures thermal plasmas thermodynamic properties is important to estimate the performances of electrical arc cutting in this gas by a circuit breaker. In this paper, air-water vapor mixtures thermal plasmas thermodynamic properties are calculated in a temperature range from 5000K to 30000K. The calculations are
carried out by supposing local thermodynamic equilibrium at pressure of 1; 5 and 10 atm. The obtained results show the influence of the water vapor initial proportion but also that of the pressure on these plasmas thermodynamic properties.

Mixture; plasma composition; thermal plasma; thermodynamic properties; circuit breakers.