On Physical Modeling of the Current Measurements in a Jet of Fire Extinguishing Agent

In accordance with the current regulations for extinguishing a fire, including without disconnecting electric power supply of direct (alternating) current of industrial frequency, fire extinguishers are allowed with a leakage current in a jet of extinguishing agent of not more than 500 µA, which is measured with an applied potential difference of 36 kV. Therefore, the recommendations for preliminary disconnection of electric power supply do not cover fire extinguishers that are certified according to the level of safe leakage current. The article deals with fire extinguishing agents based on aqueous solutions. It is obvious that the development of such fire extinguishers requires additional analytical and experimental research. The purpose of this article is the computational and physical modeling of the current leakage process, and the justification of the requirements for the parameters of the extinguishing agent flow at the outlet of the exhaust nozzle. As a result of the conducted research, the calculation methodоlogy and a scheme of the physical model of a high-voltage test bench for measuring the leakage current were developed based on measuring the active resistance of fire extinguishing agent flow in a constant voltage field and the electric capacitance of the measuring space of the test bench. The developed methodology allows to increase the reliability of the calculated results and significantly reduce the cost of working out the nozzle design. Measured at an applied voltage of 36 kV of industrial frequency, the amount of current leakage in a jet of the extinguishing agent is satisfactorily consistent with the calculation. The obtained computational and experimental results allowed to determine the range of permissible values of the active resistance and the requirements to the length of the continuous section of the jet of the extinguishing agent, which ensure safe use of the fire extinguisher for fire-fighting, including without disconnecting the electric power supply of the constant (alternating) current of industrial frequency with a voltage up to 1000 V.