Which of the following triggers the failure of successive parts?

Brownout triggers the failure of successive parts.

1.) Brownout

• It refers to a temporary reduction in voltage that directly triggers cascading failures but can affect system performance.
• Unintentional brownouts can be caused by excessive electricity demand, severe weather events, or a malfunction or error affecting electrical grid control or monitoring systems.
• Intentional brownouts are used for load reduction in an emergency, or to prevent a total grid power outage due to high demand.
   

2.) Non-cascade tripping

• Non-cascade tripping refers to a situation where a protective relay or circuit breaker does not operate in a way that isolates a faulted section of the system effectively, leading to the potential for a fault to spread and cause additional failures in other parts of the system. 
   

3.) Incipient fault in power transformer

• It indicates a developing fault, but it does not immediately lead to the failure of successive parts until it becomes a more serious issue.
• When the condition of system equipment degrades because of some electrical, thermal or chemical effects, intermittent incipient faults begin to persist in the system.
   

4.) Load shedding

• Load shedding is a controlled process used to prevent overloading and cascading failures by disconnecting certain loads or areas, so it is a preventive measure rather than a cause of cascading failures.
• Load shedding aims to prevent a power grid or power source from overloading. As a type of load management, load shedding works by rotating power outages or reducing power consumption from primary sources until demand decreases and more capacity becomes available.