Coal Fired Power Plant In-Phase Bus Transfer Simulation of Forced and Induced Draught Fan Motors

Application of fast bus transfer schemes requires high speed circuit breakers in order to minimise the dead-time during the transfer process. On the other hand, combination of high and low inertia loads such as fans, pumps and mills leads to an increase in residual bus voltage frequency decay rate; which often result in fast bus transfer scheme failing to execute. In-phase bus transfer scheme, although slower than fast bus transfer scheme; can be considered as an alternate transfer process to transfer load when main power supply is lost as a result of upstream equipment failure. Unlike in the case of fast bus transfer scheme, high decay rate of residual voltage frequency is favorable for in-phase bus transfer process; while circuit breaker closing time does not necessarily impact the performance of the transfer scheme. The paper investigates the application of in-phase bus transfer scheme to transfer load to an alternate supply when the main supply is lost in a power plant unit auxiliary power distribution system. Simulation results presented in the paper indicate that in-phase bus transfer scheme can be used to transfer draught fan motors to an alternate supply while maintaining stable boiler furnace pressure, and therefore maintain process continuity.