【作者】 王鹏；

【导师】 白焰；

【作者基本信息】 华北电力大学 ， 控制理论与控制工程， 2014， 博士

【摘要】 火电机组装机容量的不断增大、发电过程风险的不断增加,对电力安全生产提出了更高的要求,电力行业安全仪表系统的功能安全分析成为新的研究热点。炉膛安全监控系统(Furnace Safeguard Supervisory System, FSSS)作为锅炉侧保护系统,隶属安全仪表系统的范畴,并在火电机组得到了广泛的应用。本文以国际功能安全标准IEC61508、IEC61511为理论背景,结合火电厂设计的标准、规程和规定,以安全完整性等级(Safety Integrity Level, SIL)为指针,通过结构化的分析方法实现火电厂锅炉的危险与风险分析、FSSS整体目标SIL的确定,以及在役FSSS系统安全功能的功能安全评信。主要研究成果如下：(1)提出了基于连续时间马尔科夫模型的可用性评估方法。针对工业控制器的四种冗余结构,建立连续马尔可夫模型,得到要求时失效概率、安全失效概率及可用度指标的变化曲线,直观反映了不同冗余结构的性能特点,简化了求解过程。(2)改进了考虑共因失效的系统可靠性与安全性评估方法。针对串联、并联、n取k、混联等典型工业系统结构,基于改进的多重β因子模型,建立可靠性框图模型、故障树模型,得到可靠度、平均故障前时间、要求时失效概率及安全失效概率等指标的计算公式。通过对比IEC61508标准中基于简单β因子分析法得到的计算公式,证实该方法更具有一般通用性；通过实例验证,采用该方法对工业系统常用的手动跳闸按钮不同设计方案进行可靠性和安全性评估,得到正负逻辑两种跳闸方式下的最佳方案。(3)提出了基于锅炉压力容器爆炸模型的火电厂锅炉炉膛爆炸后果的分析方法。通过建立数学分析模型,得到炉膛爆炸能量及冲击波超压的量化计算方法,明确火电厂直流锅炉给水预热蒸发系统各部件不同程度爆裂产生的爆炸能量、冲击波超压大小、爆炸破坏程度及风险指数。采用保护层分析方法对火电厂锅炉炉膛爆炸可能性进行量化分析,并通过风险图、风险矩阵法确定炉膛安全监控系统的目标SIL。(4)针对炉膛安全监控系统最重要的安全功能——主燃料跳闸(Master Fuel Trip, MFT),实现硬跳闸回路的安全性与可靠性分析、MFT的功能安全评估,并通过实际SIL与目标SIL的对比,提出可行的整改措施。计算结果表明：对MFT的SIL指标影响较大的是执行器和传感器部分,逻辑控制部分影响较小。要提高FSSS的功能安全水平,必须重视执行器这个最薄弱环节,并在仪表的选择及功能测试周期的确定上进行充分考虑。更多还原

【Abstract】 With the increases of the installed capacity and power generation process risk in thermal power plants, more strict safety requirements for power production will be faced. Functional safety analysis of safety instrumented systems becomes a new hotspot in the power industry. As the protection system of the boiler, FSSS (Furnace Safety Supervisory System) is one category of safety instrumented systems, and has been widely used in thermal power plants. In this paper, based on international functional safety standards IEC61508and IEC61511, combined with the design standards, procedures and regulations of thermal power plants, and taking Safety Integrity Level (SIL) as a guiding index, hazard and risk analysis of boiler in thermal power plant through a structured analysis is achieved, the target SIL of FSSS is determined, and functional safety assessment of an in-service FSSS is made. The main results of this study are as follows:(1) The evaluation method of availability based on continuous-time Markov model is proposed. Continuous-time Markov models for four redundant structures of industrial controllers are established, curves of probability of failure on demand, probability of fail safely and availability are obtained, which directly reflect performances of different redundant structures, and simplify the solving process.(2) Reliability and safety assessment methods considering common cause failure are improved. Reliability block diagram models and fault tree models are built for typical industrial architectures-series, parallel, k out of n, hybrid, et al. Based on the improved multiple β factor model, formulas of reliability, mean time to failure, probability of failure on demand, and probability of fail safely are obtained. Compared with formulas proposed by IEC61508, which is based on simple β factor analysis method, this method is confirmed more general. By this method, reliability and safety assessments of different structures for manual trip button are evaluated, and the best solutions in two modes-positive and negative are got.(3) Explosion consequence analysis method of the boiler furnace in thermal power plant is proposed, which is based on the boiler and pressure vessel explosion models. Furnace blast energy and shockwave overpressure are quantified by mathematical analysis model. Blast energy, shockwave overpressures, explosion damage extents and risk indices for different explosion extents of the in feed water preheat evaporation system in one-through boiler are confirmed. Quantitative analysis of the explosion possibility for thermal power plant boiler furnace has been made, using layer of protection analysis method. The target SIL of FSSS has been determined through risk diagram and risk matrix method.(4) For the most important safety function of FSSS-Master Fuel Trip (MFT), safety and reliability analysis of hard trip circuit and functional safety assessment of MFT are achieved. Possible corrective measures are made by comparing the actual SIL with target SIL. The results show that:actuator and sensor have greater effects on the SIL index of MFT, compared with logic control section. To raise the functional safety level of FSSS, more importance should be attached to the actuator, and full consideration must be made in determining the functional test cycle, and the structure of instruments.更多还原