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begginings of new summary - Topic focus on how protection...

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Topic focus on how protection failures lead to cascading failures and blackouts. Hidden Failure Model looks promising An approach for modeling the protection system in transmission network reliability evaluation When protection systems are out of order, they can cause significant impacts on the network. In a study by NERC, failures in protective relays have been involved in 75% of major disturbances. Protection reliability considering the effect on power systems has had advancements. Markov model can be used to estimate simple and small problems, but the parameters become too complex for large scale systems. Fault or event trees can also be used, but there use is most beneficial for small networks, too. Protection for power systems serves two purposes: isolation of faults and protection of system components from over-voltage and over-current. All components contain their own protection devices, and when a component fails, its protection can create isolation from the system. If a breaker fails to trip, backup system protection is needed where a more extensive backup zone is tripped. In this zone, multiple components are separated from the rest of the system, which means a longer restoration process is required. In this paper, a minimal cutset method is used to model larger systems. A three state model is used for components: state before fault, state immediately after fault (in this state, active failure, a mode that causes the protection zone around the component, must be considered, and state after isolation but before repair, where passive failures, like undesired tripping and open circuits are considered. The parameters modeling breakers are: a-component short circuit from backup protective devices; FT- switching device opening without command; P s
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  • Spring '09
  • Arabshi
  • cutset, force outage failure, Transmission System Protection

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