Investigation and Experimental Verification of the Spray Intensity of Transformer Water Mist Firefighting System Under Applied Wind Speed

The outdoor transformer protection performance of fine water mist, which is widely applied to indoor electrical fire protection, is strongly affected by ambient wind. In this study, the effect of imposed wind speed on water mist distribution was quantified through a full-scale cold spray experiment conducted using a 110 kV transformer in a large wind-tunnel facility. Two nozzle configurations with flow coefficients of 2.0 and 1.7, which corresponded to nominal single-nozzle flow rates of 20 and 17 L/min, respectively, at a terminal operating pressure of 10 MPa, were tested at imposed wind speeds of 0, 4, 6, 8, and 10 m/s. Fifty-eight water collection boxes were used, including 54 boxes on the transformer sidewall and four boxes on the top surface, and the spray duration for each condition was 30 s. The wind-induced redistribution of the mist became evident at 4 m/s and intensified with increasing wind speeds. Water deposition generally decreased on the windward side and shifted toward the downwind region, while the response of the top surface differed because of geometric obstruction and the combined contribution of multiple nozzles. At the same wind speed and operating pressure, the K = 2.0 nozzle configuration maintained a more favorable spray distribution than the K = 1.7 configuration. These full-scale cold spray data clarify the wind sensitivity of outdoor transformer water mist systems and provide an experimental basis for subsequent fire tests and wind-protection design.