LV generator protection - engineering site - Schneider Electric

2.2.2. SequenceMain source / Generator Set transferTransfer generally takes place with a short break (a few seconds) the timerequired to start the Generator Set and to switch over:b switching to Generator Set sequencev loss of mains voltage at TA- load-shedding of non-priority feeders (if necessary) and important feedersv after time delay starting of Generator Set at TBv on appearance of Generator Set voltage at TC- opening of Main source circuit-breakerv closing of Replacement source circuit-breaker (Generator Set) at TDv sequenced restoration of important feedersb switching to Main source sequencev restoration of mains voltage at TAv after time delay at T'B- opening of Replacement source circuit-breaker- restoration of non-priority feedersv closing of Main source circuit-breaker at T'Cv stopping of Generator Set at T'D.E88044EE88045ENon-priorityFigure 10: Block diagram.PriorityMain Replacement MainFigure 11: Type 3 chronogram.Transfer of loads on the Generator Set, the Replacement source, impliesconsideration of the generator’s specific characteristics. This takes the form of anadditional study concerning:b the protection plan (setting and discrimination)b load management (putting back into operation)b supply of sensitive and non-linear loadsIn addition, to ensure optimised operation and maintenance, it is important toimplement additional monitoring and supervision functions (frequency and voltagemonitoring, phase unbalance, etc.).Note: return to the Main source can be performed using a synchrocoupler toensure switching without voltage breaking.15