Internal arc pressure assessment of outdoor compact substation

The medium voltage outdoor compact substations (22-33 kV) which are installed in public area should pass the internal arc test according to IEC 62271-200 Annex A for personnel safety. To design and build a prototype outdoor compact substation to withstand internal arc fault and meet all criterion, it needs to predict the arc pressure due to internal arc fault for construction of compact substation. This paper assesses internal arc pressure due to vaporized metal of compact substation in the arc process. Voltage drop of arc is evaluated in order to calculate arc pressure and the value is 22-25 V/cm. Arc energy to vaporize the metal in arc process is found to be 15.5% of three-phase or phase to phase arc energy to vaporize the copper-copper electrodes. The value of 29% of phase to ground arc energy will be used to vaporize the copper electrode and steel housing. Pressure in the compact substation due to internal arc fault is determined and the result is only 5-10% different from the measured values in arcing tests