help from any one works about protective power systems

Discussion in 'The Projects Forum' started by fifona, Apr 14, 2010.

  1. fifona

    Thread Starter New Member

    Apr 29, 2009
    i need informations about failure rates of electronic compnents,the use of fault tree analysis in protective power system,reliability analysis,station arrangements...if someone works on this or have any informations please help me.
  2. Jazz Bass Special

    New Member

    Apr 9, 2010
    In my opinion, your best bet is to consult each components manufacturer.
    Often times they will have MTBF information.
    Truthfully, what you are asking for is audacious.
    You do not specify components or specific application information.
  3. someonesdad

    Senior Member

    Jul 7, 2009
    Get thee to a library -- there's lots of information out there. I haven't worked on reliability stuff in decades, so my info is out of date. But the basics don't change.

    Getting failure rate information is easier if you work in a big company, as their reliability engineering people will collect such data. Unfortunately, the statistics depend on the failure mode and assumptions -- and predictions can be hard to verify. But there are some established methods that can help you estimate composite failure rates from part failure rates.

    People like to encapsulate the "reliability" of components into one number, usually the "mean time before failure". This is a well-defined number, but unfortunately, the distribution of failure times strongly depends on the physical mechanism of failure. And many times the failures are accelerated through some type of stress testing (often at accelerated temperatures); then there's the additional assumptions of an Arrhenius acceleration factor for a particular failure mode. When you're careful with your data and analysis, you regretfully have to admit your predictions can be off by orders of magnitude -- and this is for one failure mode. The reliability texts help you make assumptions and models to deal with the complexity.

    The US military often estimates reliability of electronic devices. As I recall, they assume exponential distributions for failure distributions, which in general is a bad assumption, but their methodology has been used as somewhat of a standard. There will be a number of documents on this topic (check the IEEE publications too), but be prepared for boring, complicated reading.

    If you have to measure and analyze failure rate data yourself, Wayne Nelson's book on life data analysis is good. Other books sitting on my shelf are: Shooman, "Probabilistic Reliability: An Engineering Approach" and "Methods for Statistical Analysis of Reliability and Life Data" by Mann, Schafer, and Singpurwalla. Another good book to have on hand is "Probability, Random Variables, and Stochastic Processes" by Papoulis. Standards are the books by Feller and Wiley or Academic Press published a two or three volume reference work on discrete and continuous probability distributions.