Hi, your lecture is very beneficial and we share common understanding mostly in EMC and earthing. But to share, new EN 50122-2:2022 informed we dont need to additional rebar or stray current collection mat on top of trackbed reinforcement anymore. Refer section 8. Also, the recent development of trackwork is to use fibre reinforced track bed. This translate to much easier construction for them. Both above means no metallic structure under the rails. But shear connector still needed as adhesion between trackbed and tunnel invert concrete. in theory this improves the insulation level of rail compared to earth. What do you think of this solution? And what would be be treatment for shear connector you think?
Thank you so much sir your lectures are very well explained and knowledgeable it helps us alot...... Thank you so much..... If possible please made lecture on transfer protection and other relaying scheme....
Thank you for interesting lecture. I have two questions, please can you help to clarify: 1. Your calculations prove that Earthed SCCS is better approach than Floating SCCS due to numbers of shear connections which are impossible to provide Epoxy/sleeve. However in accordance to Electric Lines for Electrical Railways: Planning, Design, O&M Float SCCS is recommended for DC TPS. 2. Is Structure resistance (R's) are calculated by Structure/Civil engineer during design? because TPS design normally comes at later. Secondly can R's be measured by TPS at later stage? Thank you
Many thanks. 1.As per Contact line for electric railways (2001), it recommends not to use the drainage diode solution. It is recommends to bond the stray current collection net with structural earth cable. This related to Earthed SCCS. However, both systems have been adopted in metros. But nowadays majority of the metros prefer to go with earthed SCCS in which there is no requirement to install separate SCCC. 2. Rs’ to be used can be estimated after TPS simulation. Thus, the no. of rebars required will be decided after TPS design. In order to proceed with track design without complete knowledge of Rs’, it is preferable to follow Earthed SCCS as it gives the liberty to include track rebars (which include both dedicated & structure rebars) + SEC + handrails.
There can be 3 possibilities: 1. Install copper cable, however it will not catch the stray current as it is insulated and current will enter structural reinforcement. If we provide bonding in between at particular location with rails, then it is same as return cable along the alignment to reduce rail potential. Some amount will leak to structure as it will not carry any stray current, it will just support in reducing the amount of stray current. 2. If we put bare copper conductor, then its function will be same as using rebar for stray current collection. Stray current will enter the copper conductor and then leak from it too to the nearby metallic structure (structure reinforcement, etc.). Moreover, it will be very difficult and we need to provide measure to control galvanic corrosion that will occur between two dissimilar metals, steel in concrete below rails and copper conductor. 3. Use half insulated cable, this will also lead to leakage of same amount and corrosion with steel structure as reinforcement might come in contact. Thus, it is preferable to with either Floating SCCS or earthed SCCS (with earthed being comparatively better with ease of installation).
