Turbine Control System Replacement at NPP Krško, Turbine Emergency Trip System and Moisture Separator Super Heater Control

Purpose of the project was the replacement of Turbine Control System (TCS) at Nuclear Power Plant (NPP) - Krško. From the plant construction time and the first plant start-up in 1981, the NPP TG (Turbine Generator) set was controlled and monitored by DEH (Digital Electro Hydraulic) Mod II Control System designed in 70's, based on P2500 CPU and number of I/O controllers and modules. The P2500 CPU and associated controllers were built with discrete TTL components (TTL logic chips) and the P2500 CPU had 64k of 16 bit words of ferrite core memory. For that time, DEH Mod II had sophisticated MCR (Main Control Room) HMI (Human Machine Interface) based on digital functional keyboards, one alphanumeric black & white CRT monitor and printer.

After twenty-eight years of operation and because of several other reasons, NEK decided to replace the old DEH Mod II Control system with the new Emerson Ovation' based DCS (Distributed Control System) on redundant platform for the control and monitoring of secondary plant systems in the NPP Krško, and the new system was named PDEH (Programmable Digital Electro Hydraulic) TCS.

The project enveloped implementation of PDEH system on three application platforms: BG KFSS (Background Krško NPP full scope simulator), FG KFSS (Foreground full scope replica Krško NPP full scope simulator) and PDEH system installed in the plant. The HMI for the BG KFSS platform constitutes only of soft panels or monitor graphics (all MCB - Main Control Board and its controls are available as graphic images on workstations), while the HMI for FG KFSS includes full scope replica of NEK MCR and MCB.

The new PDEH system was installed on two KFSS platforms (BG and FG) in October-November, 2008; pre-outage or on-line field installation work was performed in the January-March 2009 timeframe; while the old DEH Mod II was decommissioned and the new plant PDEH system was installed during the outage in April, 2009 and tested with the plant on line in May, 2009.


Picture 1: Old DEH and turbine monitoring NEK MCB HMI equipment before project implementation with marked-up equipment that will be removed


Picture 2: New PDEH MCB HMI equipment

The scope of project was enveloped with the basic DEH turbine control system replacement and additional functional items as listed below: 

  • Replacement of the existing DEH Mod II Turbine Control System with the new PDEH (Programmable Digital Electro Hydraulic) system built by Westinghouse Electric Corporation on Emerson Ovation DCS platform. Several functional, reliability, and HMI improvements were implemented against the existing DEH Mod II TCS (Turbine Control System).
  • Replacement of the existing Turbine ETS (Emergency Trip System) with several functional, reliability and HMI improvements against the existing Turbine ETS. Included were also replacements of hydraulic control system – single transmitters replaced with manifolds with double or triple sensors, permitting redundancy and on-line maintenance of failed sensors.
  • Replacement of the existing MSR (Moisture Separator Reheater) Control System with several functional, reliability and HMI improvements against the existing MSR Control.
  • Controls and indicating lamps that were used for remote control and testing of 12 EX (Extraction Steam) valves were removed from one of the MCR operator panels and integrated within the new PDEH. Also several reliability and HMI improvements against the existing manual controls on the MCR operator panel located behind the MCB (Main Control Board) Section A.
  • Remote control and monitoring of the main electric generator hydrogen purge system for which the new PDEH system provides HMI platform and programmable digital platform on which HMI and control algorithms have been implemented.
  • Implementation of the new PDEH system on background and foreground KFSS. 

The Sipro scope of services was electrical, I&C and mechanical engineering and design required for the development of Design Modification Package; engineering support to Westinghouse during design, installation and testing phases; as-built drawings; preparation of modification Turnover Package.

Project Manager: Marko Šegula, B.Sc.E.E.