BS 8491:2008标准适用于大直径电力电缆，其直径范围为25mm至400mm。该标准要求对电缆进行防火完整性评估，以确保其在火灾发生时能够保持完整性，防止火灾扩散和烟雾蔓延。评估方法包括对电缆进行火灾试验和热试验。

火灾试验要求将电缆暴露在火焰下，持续时间为3小时。在试验期间，要求电缆能够保持完整性，不发生燃烧和烟雾蔓延。热试验要求将电缆暴露在高温环境下，持续时间为3小时。在试验期间，要求电缆能够保持完整性，不发生燃烧和烟雾蔓延。

除了火灾试验和热试验外，BS 8491:2008还要求对电缆进行机械试验和电气试验。机械试验要求电缆能够承受一定的拉力和弯曲力，不发生破裂和断裂。电气试验要求电缆能够承受一定的电压和电流，不发生短路和断路。

BS 8491:2008还要求对电缆进行标记和标识，以便于识别和追踪。标记和标识应包括电缆型号、直径、生产日期、生产厂家等信息。

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