Abstract: High confinement of the underground substation could reduce severe explosion, scientific setting of pressure relief has become one of an important factor to ensure the safety of underground substations. The basic law of gas explosion in confined room under different combustible gas volumes and pressure relief areas were studied by small-scaled experiments. A computational fluid dynamics software FLACS was used to model the typical 220 kV underground substation and calculate the explosion overpressure of the combustible gas in the main transformer chamber by setting different gas masses and relief areas. The results show that the explosion overpressure will change from slow growth to sharp growth at a critical mass point with the increase of combustible gas mass. A nonlinear relationship between the critical mass of the leakage gas and the explosion overpressure can be discovered with the increase of the pressure relief area. A correlation of explosion overpressure and pressure relief area of 220 kV underground main transformer chamber is proposed. with the error about 11.27%.

Key words: underground substation, transformer room, explosion overpressure, pressure relief area, calculation correlation, FLACS, combustible gas