The purpose of improving the insulation of platform screen doors (PSD) is to increase the insulation resistance between PSDs and station building structure which will indirectly causes PSD and EMU having same potential. In this case where voltage difference between PSDs and EMUs are avoided, electric shocks that may be experienced by passengers and station staffs can be prevented. If PSDs unfortunately encounter grounding failure, the negative return current in the rail may burn the control unit circuit board of the PSD. Since the PSD s and rail tracks adopted floating grounding, the insulation resistance between PSD and station structure is regulated to exceed 0.3MΩ/250Vdc.
Upon on-site inspection and test results, insufficient insulation areas were discovered and the MRT Engineering Office of BOHSR demanded the contractor to show correction and improvement. Reasons of insufficient insulation include design factors such as damages of the insulation gasket caused by uneven pressure and the additional base plate causing the insulation gap being too narrow; Construction factors such as extended stationary bolts of piers causing direct contact with the door frame, improper installation of metal washers resulting in direct contact with the base, iron scraps of segmented bolts were not properly removed, and uneven surfaces were not corrected and smoothed. In addition, the PSD contractor should hold CIP meetings with civil engineering tender contractors in advance for verification to prevent disturbing issues such as torn up sandbags causing Cement Asphalt Mortar to fill up the platform door base grooves and disrupts insulation.
After correcting the above deficiencies, insulation still fluctuation on account of weather change (fog, rain, etc.) at some stations. Fortunately, the door panels are anodized and an insulation film is applied under the platform surface within 2.5m range nearby PSD so that there would be no casualties if this happens.