Notes455_2 - Purpose: Research and broadly understand...

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Purpose: Research and broadly understand hidden failures in protection systems while also tying in cascading outages Hidden failures may originate from almost any part of the power system. Protection systems are made of components such as relays, current and voltage transformers, circuit breakers, relays, etc. to help deter the effect such failures may have on the system. Hidden failures can also be found in these protection devices causing a complex analysis that is needed to take into account when researching potential catastrophic hazards. Currently, the focal point of most research in regards to hidden failure analysis is being conducted on relays. Due to this, other elements which may be the origin of hidden failures are less studied therefore leaving gaps in creating a more reliable system. With the increased efforts in providing more reliable power systems numerous electronic devices such as phasor measurement units and digital protection relays have been integrated into the operation of generating and distributing electricity. Although these devices have vastly improved the reliability of day-to-day operations there are still many improvements than can be made in areas such as circuit breakers. The functionality of circuit breaker trip mechanisms cannot be observed using the same devices previously stated. Hidden failures can go undetected due to faulty circuit breaker trip mechanisms therefore degrading the dependability of the system. This can lead to the possible failures of a circuit breaker failing to open. Possible Hidden Failures Current Xformer- Due to a fault the current transformer may become saturated. If this occurs naturally the transformer will not operate properly therefore secondary currents cannot be properly related to the primary current. Voltage Xformer- For example a coupling capacitor voltage transformer, the output voltage of the transformer may drastically differ from the primary voltage after the fault Relay- May fail to or incorrectly detect system changes therefore causing unnecessary trips in parts of the system Circuit Breaker- Circuit breaker plates may fail to open due to high voltage or current levels causing the plates to fuse together. Also the trip coils can be open circuited.
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Notes455_2 - Purpose: Research and broadly understand...

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