The probability of failure on demand (PFD) for an emergency generator system is important when electrical power is needed to protect humans from harm or to prevent equipment damage. To evaluate the PFD for an emergency power system (EPS), we must consider:

• All the components for the fuel, the controls, the transfer switches, and the circuit breakers in the emergency load feeders.
• The capability of the weekly, monthly, semiannual, annual, and four-year inspections and proof tests to detect all the failure modes that can prevent correct operation of the generator system.

中文翻译：

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两台满负荷发电机——为什么计算出的应急电力系统按需发生故障的概率如此之高？

当需要电力来保护人类免受伤害或防止设备​​损坏时，应急发电机系统的按需故障概率 (PFD) 很重要。要评估应急电源系统 (EPS) 的 PFD，我们必须考虑：

• 紧急负载馈线中的燃料、控制装置、转换开关和断路器的所有组件。
• 每周、每月、每半年、每年和四年的检查和验证测试的能力，以检测可能阻止发电机系统正确运行的所有故障模式。