doi:10.3850/978-981-08-6396-8_T3-01

ABSTRACT

An underground 66kV electrical substation (ESS) has been planned on the Singapore Downtown Line (DTL) mass rapid transit system project. The ESS, along with the other substations, provides power to the entire DTL. The ESS will be the first substation of its kind in Singapore to be located entirely underground to facilitate better use of land while providing good integration with the surrounding environment. There will be four 66kV/22kV transformers housed in individual rooms in the ESS. This paper is to outline the approach and considerations in substituting the deluge with water mist system. The standard provision is to provide a deluge system and its associated supporting E&M services. Water mist system has advantages over the conventional water spray system. It provides microdroplets, and therefore requires low water flow quantity to extinguish fires by rapid vaporization, local oxygen depletion and maximum heat absorption.

A Computational Fluid Dynamics (CFD) study was carried out to compare the heat removing effort between traditional water spray system and water mist system for a fire on the transformer. The comparison study has shown similar effect between the two systems by assessing the temperature in the space. However, in reviewing the benefits given by the water mist system such as fire fighting water consumption, pump size, pipeworks, as well as large drainage pump capacity and sump pit size required for disposing the water, the benefits of adopting water mist system in this underground ESS are apparent.

This paper addressed the comparison of the water mist system and water spray system in the ESS by CFD simulation results as well as other design validation tools in deciding the more suitable fire extinguishing system for the transformer rooms.

Keywords: Water mist, Underground, Transformer.

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