Research On The Cable Failure Characteristics And Prediction Method Under Fire Conditions

As one of the most important element to cause exacerbate disaster,there is a great deal of cables losing operating ability in fire processes.In order to provide scientific basis and practicable technology for cables quantitive screening,life-cycle management and fire probabilistic risk assessment of cables engineering,it is necessary to realize cable failure characteristics in fire.The research is of great importance to increasing safety management skill of important projects and avoiding tremendous security disasters.The simulated fire experimental investigation was conducted on SDR-1 cable heat radiation testing table,and cables samples include YJV,ZR-VV,WDZ-HK3-PYJP3YJP3 and ZR-KYJV.The influence of materials,structure and size,and core quantity on cable failure characteristics was analyzed.The dominant element and influence principles were determined.Insulation layer material was the dominant element which influenced cable insulation failure temperature,and determined the vulnerability of cable under thermal damage.Other cable internal structure factors were the dominant factors that influenced cable insulation failure time,and determined heat transference process from outside to inside.The influence of weathering ageing on cable failure characteristics have been studied experimentally.SDR-1 cable heat radiation testing table was used to provide several simulated fire conditions.And YJV,ZR-VV and WDZ-HK3-PYJP3YJP3 cable samples after heat ageing,ultraviolet ageing and ozone ageing were selected.The impact of weathering ageing form and ageing time on cable failure characteristics of thermoplastic cables and thermosetting cables was systematically analyzed.The research revealed the differences of influence laws and degrees of heat,sunshine and ozone on thermoplastic cables and thermosetting cables.By stretching cable ageing life curve,the link between cable insulation failure temperature and practical served time,the link between cable insulation failure time and practical served time were established.The simplified physical model of a single cable with a unidimensional three-layer structure and the simplified scheme for bundled cables were presented in this article.And the cable insulation failure prediction method was conducted.By constructing microelement heat transmission differential equation,the internal temperature of cable was calculated,and a series of cable insulation failure prediction models with different laying patterns were established.By simplifying the internal layer cables or external layer cables of bunch of cables,cable insulation failure prediction models for bundled cables were established.Combined with practical examples,the article analyzed cable insulation failure probability with different laying patterns in fire of switching room of nuclear power plant.