The article introduces the structural features, operation mode of the China CRH-series EMU braking system by the example of CRH2. Then, the article analyses the safe-protection measure of each sub-system of EMU braking system in detail, such as braking control system, wind-source, basic braking system and electric braking system. Basing on the analysis, it classifies the braking fault into four types according to the principle of whether the EMU can continue to run safely. Afterwards, the article calculates the braking distance of the fault type III and IV and draws the conclusion; 1 ) When the braking power decreases by 1/8 or more, it will be unable to ensure that the EMU does not overrun the stop signal even if ATP system works well still. 2) The probability of overrunning the stop signal will be greater when the train runs in lower speed, and then the distance of overrunning the stop signal will be longer when the train in higher speed. 3) After the braking power decreases to some extent, EMU will probably exceed the permissible turnout speed when entering into the station via branch line, and there exists the risk of EMU's rolling over. Altogether, after braking system faults, it will be unable to ensure the EMU running safely only by using the method of manual-speed-restriction, so it is necessary to apply more effective safe-protect ways.%以CRH2为例,介绍我国CRH系列动车组制动系统的结构特点、工作模式,对动车组制动系统中的各子系统(如制动控制系统、风源、基础制动系统、电制动系统等)自身的安全保障措施进行了详细剖析,并以此为基础,按照动车组制动系统故障后是否可以继续安全行车的分类原则将制动系统故障归纳为四类,之后对涉及到运行安全的第Ⅲ、Ⅳ类故障进行制动距离计算,得出的结论是:只要动车组的制动力下降幅度≥1/8,列控系统即使处于完全监控模式,也不能保证动车组列车不冒进停车信号；而且列车速度较低时,冒进信号的几率较大,速度较高时,冒进信号的距离较大；另外,当制动力下降到一定程度后,列车在侧向进站的过程中还有可能超过道岔规定限速,存在侧翻的危险隐患.因此,动车组制动系统故障后仅用人工限速的措施并不能保证行车安全,必须采取更加有效的安全防护对策.
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