Tuesday, July 5, 2011

FBD-based PLC program from NuSCR





This article expresses a methodical process of generating FBD-based PLC program from NuSCR requirement with permanent set-point increasing trip with running bypass instance included in the specifications for Reactor Protection System (RPS). After for a moment initiating the tour logic, it introduces NuSCR key features and programming of FBD.

Background of Reactor Protection System
The system protection of KNICS digital plant contains of three subsystems: automatic test and interface processor (ATIP), RPS, and engineering safety features-component control system (ESF-CCS). RPS divided into coincidence processor (CP) and BP, employs trip logics so the plant can be shut down safely in situations of emergency for example enlarged reactor temperature or defeat of coolant. EFS-CCS, it is similar in features to RPS, efforts to decrease influence of other reactor industrial accidents while ATIP occasionally tests EFS-CCS and RPS so that safety of plant is always guaranteed. BP recognizes inputs from 18 diverse sensors and carries out required calculations to supervise the status of reactor’s safety. Amongst some trip logics, unchanging set-point increasing trip with operating bypass produces the trip signal (th_X_Trip) if value of input f_X increases above the value of predefined threshold. Nevertheless, trip logic has to be bypassed if a user presses the button of bypass while the value of input stays in the permitted and normal range. Preliminary and different trip logic, whose set point is faintly lesser than that of the trip, warns a user of potentially imminent trip. The system is pretty complicated in that specifications for CP and BP alone in NuSCR go over 400 pages. All 4 BPs redundant copies and a CP are applied on divide PLCs and performed occasionally.

NuSCR gets better articulateness of the document and readability of the requirement of SCR. it explains features of the syntax NuSCR and formal semantics in detail, and it reports a NuSCR-based specifications of environment engineering namely NuEditor. It momentarily of assessments only on the necessary features to understand how code of FBD is synthesized from NuSCR. The function overview diagram (FOD), in document alike to the diagrams of data-flow, imprisons dependence relative among a variety of nodes hierarchically so that complicated specifications can be identified in a fashion of divide-and-conquer. FOD for e.g_Fixed_Setpoint_Rising_Trip_with_OB demonstrates the overall structure for permanent set-point dropping trip logic. It is a NuEditor screen-dump. The nodes of rectangular designate outputs and inputs, and different types of nodules are drawn in diverse color and shape so that the functions are obvious visually.



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