IEC 60870-4:1990 pdf free download – Telecontrol equipmentand systems
lt is intcnded that this part serves as a common platform for thesystem planner and the ‘supplier or manufacturer ofteiecontroisystems. The system planner will find the contentshelpful indetermining the requirements for a particuiar teiecontroi system. inaddition,these rules provide a means of comparing the products ofdifferent suppiiers. The supplier or manufacturer will find guidelinesforthesystem design and a base forclassification of systemperformance.
Thispartcomprises a main body, which containsthe actualstandard, together with twoappendices， which contain furtherinformation and recommendations.
The main body is devoted chiefly to a treatment of the variouscharacteristics as operational parameters. A short description of eachoperational parameter isfollowed by a listofthenecessaryperformance requirements and,where feasible,a classification of theoperational parameters in performance classes .
The performance classes serve to specify the system requirementsfor a particular application and to evaluate the system performance ofdifferent telecontroi systems.
The performanceciasses usedare to be optimized foreachapplication and agreed upon between the user and the supplier .
3. Classification of operationa! parameters
This clause covers those properties which infiuence the performanceof telecontrol systems. Appropriate requirements and,where feasible,performance ciasses have been specified for each of lhe propertiescovered.
The classification ratings given apply in general to the performanceof the units of the ovcrall system. The performance of ‘the overal!system shall be derived from the performance of all components of atelecontrol system (in the restricted sense)，excluding the process andthe operator sequipment. Certain properties , however， such asreliability and availability, can be applied as performance criteria toindividuai items of equipment. The components of an overali systemare, for instance:
3.1 Rellabllity
Reliability is defined as a measure of an equipment or system to perform its intended function under specified conditions for a specified period of time (see 1EC Publications 271, 271A and 300). it is a probability figure, based on failure data and length of operating time.
The reliability of a telecontrol system is expressed by the” mean time between failures” in hours (MTBF)， and can be caiculated from the reliability figures of the individual system components (see the standards of T echnical Committee No. 56).
The reliability of a system depends on the following factors:
-the relibillity of the system equipment and the software;
-the configuration of the system.
Measures which may enhance the reliability are listed in appendix A, clause A.1.
3.1.1 Rellabllty requirements
The overall system reliability and partial reliabilities of certain specified sections of the teiecontroi system are to be caicuiated by the supplier from the reliability figures of the individual comonents, and proved against the actuai performance in the field over a given tria period. The start and duration of the trial period should be agreed upon between the supplier and the user and should exclude the early failure period.
The equipment supplier should provide on request failure distri-bution data for aii components. assemblies and units which, on failure,could cause loss of a function or malfunction of the system.
The failure modes and the effects of failures on the system performance shall be analysed by the supplier and the results made available on request.