Advanced methods of intrinsic safety

Again and again, testing houses, manufacturers and users of intrinsically safe products have put the question, how could the narrow borderlines of classic intrinsic safety concerning available power be passed over These borderlines are determined by reference curves as well as by installation rules. The following approaches are dealt with in more detail below  

In certification practice, the so-called intrinsically safe systems are known as well. Deviating from a (single) apparatus which is certified individually, an interconnection of several apparatus is under consideration for an intrinsically safe system, including the connecting cables for the most part. Several intrinsically safe circuits and different categories of these circuits as a part of an intrinsically safe system are permissible. 

The standard EN 50039 permits uncertified systems, too. In this case, type of protection intrinsic safety shall be established by knowledge of the data of all apparatus including those not certified and the cables. 

This proof is subject to experts in most cases. Documentation as a system s description is imperative. 

In addition, it may be mentioned as a special feature of intrinsically safe systems that a fault analysis (as an assessment for individual apparatus) (two faults are assumed for category ia, one fault for category ib) may be applied to the system as a total and not to each individual apparatus. 

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