Kolkata Metro Rail Corporation (KMRC), carried out tests in the stretch between Salt Lake Stadium and Phoolbagan on Wednesday evening to check whether the third rails inside the tunnels are properly aligned with the Third Rail Current Collectors (TRCCs) or Current Collection Devices (CCDs) attached to the rakes.
In case the alignment is not proper, the rakes would not be able to draw power from the third rail and there would be flashing. “These tests are crucial as Metro plans to throw open the stretch till Phoolbagan in the next three months. Once this happens, a jump in the number of passengers is expected and we want unhindered services.
Normal tests that are carried out in the elevated stretch aren’t possible inside the tunnels as there isn’t any WiFi or GPRS connectivity. The main aim is to locate the position of the CCDs with respect to the third rail pedestals. Unless this happens, it is not possible to identify the exact spot where flashing occurred due to a problem in the alignment of the third rail,” the source said.
To find out the exact location of flashes (sparks), if any, permanent magnets are fitted in the wheels. Sensors are then fitted facing the wheels to measure the magnetic flux. The sensor then acts as a counter. As the diameter of a wheel is known, the distance and speed is properly mapped using a software. Using encoders, starting chainages are fed into the software and calibrated with the run. This provides the exact position of any CCD. The margin of error is less than 0.5%, the source said.
“Flashes inside the tunnel can disrupt services and damage equipment in the long run. At times, there can be smoke emission causing distress to passengers. Any stoppage may also require emergency evacuation. This test is important to avoid all this,” the source added.