REPLACEMENT OF CERNAVODA UNIT 2 BOP OBSOLETE CONTROL EQUIPMENT BY DISTRiBUTED CONTROL SYSTEM DCS

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REPLACEMENT OF CERNAVODA UNIT 2 BOPOBSOLETE
CONTROL EQUIPMENT BY DISTRiBUTED CONTROL SYSTEM
(DCS)
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UNIT 1 BOP Control Architecture

• At Cernavoda NPP Unit 1 the control functions
  related to BOP areas and Support Systems were
  provided by some different systems
• - Nuovo Pignone for Analogue Control
• - Leeds Northrup for Winding Temperature
  Supervisory system (temperature signals related
  to motors, compressors and transformers)
• - Marconi for Digital Control
• - ORTEC panels in Main Control Room (MCR), for
  control, indication and supervision functions
• - other dedicated local panels for the
  integrated Support Systems (Pump- House, HVAC and
  D2O tower systems), such as York cubicle for
  Chillers, AECL / Gec-Alstom for Sequencers or
  Romanian products.

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• The technology of these systems was mainly
  based on hardware interconnections point to
  point between field instruments, logic cabinets
  in Equipment Room (E/R), with electronic cards
  and cabled static elements, and a conventional
  operator interface in Main Control Room (MCR)
  with hand switches / push-buttons,
  electro-mechanical indicators (EMI) and different
  signalization lights (alarms, status, ...).
  Functional Group commands for Digital Control,
  with the single component commands located inside
  the logic cabinets in E/R, or from local panels
  close to the equipment in field were also
  available.
• The digital signals to/from the field or MCR,
  conditioned and manipulated in local
  instrumentation panels, were transmitted to/from
  Marconi cabinets passing through a Central
  Distribution Frame (CDF) located in E/R. The
  dispatching function of the signals between the
  various CI components (included Plant Computers
  (DCC X/Y), for trending, data logging,
  supervision activities, and some control
  functions) was provided by CDF.

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UNIT 2 BOP Control Architecture

• In Unit 2 all the different and formerly
  foreseen Control Systems are replaced with a
  single product, a Distributed Control System
  based on processor technology, able to integrate
  all typical control functions (modulating and
  digital controls, supervision and alarm, etc.),
  and to use an advanced Operator Interface too.
• The DCS Automation Nodes are distributed over
  the Plant, located as close as possible to the
  process areas where the controlled components and
  sensors are. Commands/signals to/from MCR are
  handled by cabinets located in the adjacent E/R.
  All the signals are multiplexed, the cabling and
  terminal connections numbers are reduced, the
  cable-trays layout are optimized, and the
  communication buses run all over the BOP area.
• The Unit 2 BOP Control Architecture includes
  the traditional MCR operator interface (hand
  switches / pushbuttons, electro-mechanical
  indicators, lamps, window tiles) already supplied
  for MCR.
• Only the A/M Stations for manual modulating
  control located onto the MCR boards has been
  replaced by new corresponding DCS units (with a
  little carpentry arrangement only), so keeping
  the same functional interface by the operator
  point of view. The other A/M Stations and digital
  manual units located in E/R will be replaced by
  Virtual Control Panels onto an Operator Station.

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• Software Operator Stations are also used for
  the Winding Temperature Supervisory system, for
  the overall BOP supervision, including the
  control of some Support Systems (Pump-House,
  HVAC, D2O Up-grading, partially Chillers,
  Compressors and Stand-by Diesel Generator
  Sequencer functions).
• These Operator Stations will be distributed
  over the Plant. An Engineering Work Station (EWS)
  for Configuration and Tuning functions is
  provided too.
• The DCS main features base on open
  architecture, modularity, expandability, high
  reliability, respect of the safety constraints,
  ease of use and of keeping pace with further
  technology evolution.
• Dedicated requirements are easily implemented
  in terms of Redundancy, Channelization,
  Functional Partitioning, Fault-tolerance, Safe
  failure modes, and are detailed in the
  followings. But evident advantages are also
  obtained by considering the amount of hardware
  reduction, the flexibility of software
  optimization and the high standardization degree,
  which permits drastically lowering the
  implementation working efforts. Test,
  installation, commissioning, operating and
  maintenance activities can be made simpler than
  in case of a traditional hard-wired approach.

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Criteria to allocate I/O signals into the DCS
cabinets

• The DCS Architecture is influenced by the
  fulfillment of some general Design Criteria
• - geographical distribution of DCS equipment
  (function of I/O signals location too),
• - redundancy of all critical components
  (multifunction controller, communication
  interface and bus, power source)
• - channelisation (Even/Odd lines),
• - functional partitioning of Plant systems
  (partitions 1/2/3 or NP1/NP2/NP3),
• - categorisation of Plant systems
  (Safety/Non-Safety Related systems).
• These criteria have to be achieved also
  considering to optimize the Automation System
  performances (as response time, global
  throughput, data traffic on communication bus,
  ...), and to conform reliability/availability to
  Plant demands.
• It is requested to have a separation by the
  point of view of either the hardware
  configuration or the software implementation.

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• There is a hierarchy among the previous
  criteria
• - identify the different Plant areas where DCS
  cabinets should be placed
• - assume the proper redundancy of DCS
  master/slave modules (influencing the cabinets
  layout)
• - analyze the Channelization (Even/Odd lines)
• - separate the signals considering the
  Functional Partitioning criteria
• - separate the signals by the Categorization
  criteria (if it is possible)
• Hence, the input signals shall be grouped,
  considering the location of instruments, local
  panels and controlled devices and the appropriate
  distribution of DCS cabinets. These groups
  include all signals pertaining to each Even or
  Odd line, separated successively among the
  Partitions 1, 2, 3, NP1, NP2 and NP3 (and Safety
  or Non-Safety Related systems too). All the
  involved Plant signals will be distributed
  between the resulting different sub-groups, and
  correctly assigned to different DCS cabinets.
• The following flowchart, (F1), identifies the
  sequential steps to define the I/O signals
  allocation into DCS cabinets, in accordance with
  the hierarchic structure formerly noted (and also
  considering an appropriate internal layout of DCS
  cabinets).

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Geographical Distribution of DCS cabinets

• Considering the BOP signals handled (for
  acquisition/actuation functions), and their
  availability all over the Plant included also
  those related to Pump-House, HVAC and .D2O
  Up-grading. systems and taking into account the
  former assumptions the geographical localization
  of DCS cabinets involves the following areas
• - Turbine building (T/B el. 100)
• - Electrical Bay (E/B) Even (el. 111.5) and
  Odd (el. 121.5) Rooms
• - Equipment Room (E/R - Service building (S/B)
  el.109)
• - Chillers building (C/B)
• - Pump-House (P/H) Control Room (el. 103)
• - HVAC Control Room (Heater Bay (H/B) el. 127)
• - D2O tower Control Room (el. 105)
• - Stand by Diesel Generators Building

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Channelization

• DCS cabinets manage all the signals correlated
  to the equipment and devices in field and on the
  MCR local panels, are supplied either by Even or
  Odd power supply lines in each Plant area and are
  interconnected to separated Even or Odd DCS
  networks (both redundant). These signals shall be
  mainly assigned to the Even or Odd channel, and
  consequently to the Even and Odd DCS cabinets, in
  accordance with the following rules and criteria
• - the signals shall be assigned to the same
  channel to which the process equipment or device
  is associated
• - the signals shall be assigned to the separated
  Even and Odd channel when redundant process
  equipment or devices are used,
• - where the above two rules do not apply, the
  signals shall be mainly assigned in order to
  achieve a balance between channels.
• Even/Odd Channelization requirement has to be
  fulfilled also for the signals associated to the
  digital (by conventional HS/PB units) and
  modulating controls (by A/M Stations supplied
  with DCS equipment) that are located inside the
  MCR boards, and displayed onto a Software
  Operator Station (Virtual Control Panel) in E/R
  or anyway.

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Functional Partitioning

• In consequence of the Functional Partitioning
  requirement stated before, the signals belonging
  to
• - Instrument Air (75100-.) systems
• - Main Feed-Water (43230) and Condensate
  (43210-43220) systems
• - Service Water (71300-71340-71350) systems
  shall be allocated in separated DCS cabinets.
• All the just defined systems are Safety Related
  systems.
• This requirement, although not strictly
  mandatory, has been adopted to permit also a
  physical separation that shall assure an
  independent functionality for the three
  partitions.
• The first set of DCS cabinets is defined
  Partition 1 (e.g., Process Control Unit 01, 02,
  05, 06, 09, 10,.) the second set of cabinets is
  defined Partition 2 (e.g., Process Control Unit
  03, 04, 07, 08, 11, 12,.) the third set of
  cabinets is defined Partition 3 (e.g., Process
  Control Unit 13, 14).
• With Process Control Unit is intended the DCS
  standard logic cabinet with the associated
  termination units cabinets.
• Once the process systems defined in the
  previous step are assigned to DCS cabinets of
  Partitions 1, 2 and 3, the other signals to
  integrate into the DCS Architecture (pertaining
  either to Safety or Non-Safety Related systems)
  are successively associated to the DCS Process
  Control Units.

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Functional Partitioning

• For these signals, as stated before, a
  Partition NP (non partitioned), and a
  successive grouping in three sub-groups
  identified as NP1, NP2 and NP3, has been
  conventionally defined. They can be allocated
  together the signals associated to Partition 1, 2
  and 3 without any peculiar constraint (in the
  related cabinets PCU 01, 02, 03, 04, ., 13, 14).
  The association of these signals to one of the
  above listed Partitions is mainly based on
  functional considerations, process correlation
  and/or some specific conveniences (homogeneity
  and acceptable filling of DCS cabinets,
  considering also the requested .free space. to
  provide, etc.).
• However, at the present time most of the signal
  of the systems collected in Partition sub-group
  NP1 have been allocated with the systems
  identified as Partition 1, those pertaining to
  Partition sub-group NP2 with the systems
  identified as Partition 2, and those pertaining
  to Partition sub-group NP3 with the systems
  identified as Partition 3.

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Categorization

• The signals related to Safety and Non-Safety
  Related systems could be assigned to different
  I/O slaves, placed in different racks of the same
  logic cabinet.
• The separation between safety and not-safety
  related systems, although not required by DCS
  Design requirements, is opportune for a clean
  panel filling, from a design point of view, and
  for a more functional Plant operability and
  maintenance activity, but it is not strictly
  mandatory.

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Additional Requirements

• The standard signals associated to A/M Stations
  for modulating control (e.g. 1AI, 1AO, 1DI and
  1DO) must be collected together, associated to a
  specific DCS I/O Slave module and a related
  conditioning unit to put inside the proper DCS
  cabinets.
• All conventional A/M Stations are located on
  the MCR boards and the related signals are
  allocated and assigned to the same Partition of
  the controlled device, thus they too achieve the
  partitioning rules already defined.

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DISTRIBUTED CONTROL SYSTEM (DCS) HARDWARE

• This section describes the physical arrangement
  and technical architecture of the Distributed
  Control System (DCS) related to the Cernavoda
  Unit 2 NPP.

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General Description

• The implemented Automation Architecture
  consists of a number of Processing Control Unit
  (PCU) cabinets, of associated Termination Unit
  (TU) cabinets, of some communication loops, of
  communication bridges between them, of all the
  required cabling and connections. The cabling may
  be of various types (hardwiring, optical fibers),
  depending on the particular functions.
• It reflects the general functional philosophy
  of Odd/Even separation and some other criteria
  (e.g.Partition) within each process system.
• In each PCU cabinet there are a number of
  digital processing electronic equipment modules,
  plus power supplies, cooling fans, racks with
  connections. The number of functional modules
  varies from a cabinet to another. Each PCU
  cabinet contains processor modules, a
  communication port, plus a number of slave
  analog/digital input/output modules (for a total
  of at most 96 electronic cards). The TU cabinets
  only contain input and output termination unit
  module cards.
• Each equipment of the DCS is housed in steel
  cabinets, except for the display monitors and
  peripheral equipment.

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• The DCS performs the following control
  functions in an integrated solution
• - Closed Loop Control
• - Open Loop Control
• - Alarm Management
• - Plant Supervision
• - Signal acquisition, conditioning and
  management.
• The DCS for CERNAVODA Unit 2 NPP is an
  Integrated Process Automation System based on the
  ABB Symphony Harmony Rack I/O System with TENORE
  Operator Interface Stations.
• Specifically designed for process management,
  Symphony Harmony System architecture is based on
  the high speed, high throughput (10 Mb), and high
  security C-NET Data Highway.
• C-NET is a scaleable and unidirectional Control
  Network, forming a ring to grant a higher
  security, which connects all the Process Control
  Units (PCUs) and the TENORE Operator Interface
  Stations (OIU).

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• Several C-NET rings are connected together by
  means of Bridge devices (INIIL/INIIR) in a STAR
  configuration.
• The heart of Symphony Harmony is the Multi
  Function Processor (MFP) module, that is the
  equivalent of a stand-alone process computer
  without the added complexity. Each MFP processes
  the downloaded control program, which implements
  the control strategies, handling thousands of
  analog and/or digital Input/Outputs.
• The MFP communicates with I/O modules (Slaves)
  by means of the Expander Bus, a high-speed
  parallel bus, and with the other MFP.s and the
  C-NET node of the PCU by means of the Control
  Way, 1 Mb Ethernet type network.
• The Symphony Harmony multi-layered hierarchical
  communication architecture is represented in the
  following Figure 1.

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System Overview

• The following Figure 2 shows the general layout
  of the DCS dedicated to Cernavoda Unit 2.

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