tender for retrofitting of existing hpa 12/1640, 12 kv,1600 a sf-6 gas circuit breaker with vacuum circuit breaker including supply, dismantling, erection , commissioning and testing of the new v.c.b at ph-i, sgtps, mppgcl, birsinghpur. , supply part , supply and retrofitting of vacuum circuit breaker (type siemens-3ae55666 / abb-vd4-hpa.12.1640/ equivalent model) (one to one retrofit againest existing hpa 12/1640, 12 kv,1600 a sf-6 gas circuit breaker) , work part , retrofitting solution , including, dismantling work of existing abb make hpa 12/1640, 12 kv, 1600 annual periodical maintenance sf-6 gas c.b. and erection, commissioning & testing of supplied v.c.b