LTA and SMRT identify cause of major train disruption on July 7th

The Land Transport Authority (LTA) and SMRT have pinpointed a contaminated electrical component as the cause of a massive disruption that crippled the entire East-West and North-South lines on July 7^th, reported The Straits Times. Salt deposits had accumulated on an insulator for the power-supplying third rail along a stretch of the East-West Line between Tanjong Pagar and Raffles Place stations.

In a media briefing some three weeks after the incident, LTA Deputy Chief Executive for Infrastructure and Development Chua Chong Kheng said a tunnel leak at that stretch resulted in water with high chloride content dripping near one of these rail insulators. This led to surface contamination of the insulator, hence reducing its effectiveness.

Mr. Chua said there were other third rail insulators that were also found with weak electrical resistance. The insulators insulate the electrified third rail from the ground and ensure that electricity from the third rail only flows to the trains via the trains' current collector shoes. The contaminated insulator resulted in a higher than normal voltage difference between the running rail and the ground, he said. It was this higher-than-usual voltage difference that tripped the power system.

As a follow-up measure, SMRT is changing out third rail insulators with low resistance in the next four to six weeks. The eventual plan is to replace all 30,000 insulators on the network with new one. SMRT aims to change out 16,000 of them by the first quarter of 2016, and the remaining 14,000 by the first quarter of 2017.