Against the triple redundancy and quadruple redundancy structure of turbine protection system(ETS)

the paper studies the failure model of different redundancy structures

and analyzes the transformation process of the ETS redundancy structure from normal state to degrade status and failure status. Moreover

it establishes the reliability model of the triple redundancy and quadruple redundancy ETS by using the Markov model

and investigates the reliability of the ETS with different redundancy structures from both the aspects of safety failure ratio and functional test cycle. The simulation researches prove that

when the probability of danger failure is larger

using the quadruple redundancy structure can better improve the ETS's MTTF than using the triple redundancy structure. When the probability of safety failure is larger

using the triple redundancy structure can better improve the ETS's MTTF than using the quadruple redundancy structure. Using the quadruple redundancy structure can better prevent ETS refused action and allow longer functional test cycle than using the triple redundancy structure.