Protection Modification to Avoid Surge Arrester Failure Jawale Girish1, Gawde Yatin1, Joshi Surendra1 1The Tata Power Company Limited, Mumbai Online published on 16 April, 2022. Abstract The Tata Power Company (TPC) is the largest integrated private sector utility in the business of Power Generation, Transmission and Distribution in India. It has installed capacity of Generation of 13068 MW in india and presence in all segments of power sector viz fuel & logistics, Generation (Thermal, Hydro, and Renewables), Transmission, Distribution. Tata Power caters to variety of customers like, Distribution Utilities, Large, Medium & Small scale industries, Refineries, Railways, commercial and residential buildings etc. in Mumbai, it has its own transmission network of 220 kV and 110 kV within the Mumbai City. Earlier, the Railway traction supply was fed from Receiving stations on 22 kV and at Traction s/s the supply was converted to 1.5 kV DC for Electrical Locomotives (Local Trains) in Mumbai City. All other trains in PAN India are running on AC supply except in Mumbai. Recently, Railways have converted their traction system from 1.5kV DC system to 25kV AC System inside the Mumbai City also for nationwide standardization. The Railways traction s/s are now fed by Tata Power through two phase supply from the receiving station on 110 kV and Further it is stepped down through 110/25 kV Traction Transformer as Single Phase Traction Supply. One terminal on 25 kV side is grounded and other terminal runs along the train (catenary) for traction supply. All the traction load is fed from 25 kV side. Two nos. 110 kV/25 kV Transformers are available in the traction s/s. There is a provision of paralleling of these two transformers on 25 kV side. Even paralleling of feeders fed from two different stations is also possible through 25 kV SP/SSP sectionalisers. Even though, as a normal operating philosophy the transformers are operated sectionalized mode, depending upon the load requirement, the supplies are paralleled on 25 kV side. At present construction of Metro Railway is in progress and Metro is supplied through three phase supply but at Metro end, traction load is fed through single phase supply from Metro end and other station supply is on three phase supply system. The traction supply arrangement is similar to Railway supply i.e. through single phase transformer. The Supply to Railways as well as Metro is through cable network, hence to avoid damage to cables due to switching, Surge arresters are provided at sending end as well as receiving end. The supply end is Either AIS (Air insulated switchgear) or GIS (Gas Insulated Switchgear). It is observed that SAs (Surge Arresters) are failing if there is any cable fault as the transformers are parallel on 25 kV Catenary side or two sources from different stations are paralleled through 25 kV catenary. This phenomenon is noticed even though the fault is cleared within 100 mS. The Paper describes detailed analysis of Protection operation during the Occurrence along with the disturbance Records. To avoid such recurrence of such incidences, modification in Protection, incorporation of additional protection is carried out as per the analysis and recommendations and all these modifications, the reason behind the modification etc is given in detail in the paper. Top Keywords Railway, Metro, Traction, Surge Arrester, Protection TPC. Top |