3.distributed_control_systems.pptx

7/27/2019 3.Distributed_Control_Systems.pptx

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Distributed Control Systems


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Dedicated Computer Control


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Dedicated computer control have wide

applications in

Small plant operation

Large scale operations

Signal and Image processing, etc.


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Essential functions of a computer

Process monitoring

Data acquisition

Alarming and signaling Data processing

Data archiving

Process control


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Centralized computer control


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Distributed Vs centralized computer

control


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De-Centralized computer control

system


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Evolution of DCS


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Famous DCS


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Functional requirements of distributed

computer control system


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Plant operator requirements


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Maintenance engineering

requirements


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Design/Development Engineer

requirements


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Manager/Supervisor requirements


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System Architecture


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DCS Hierarchy Structure


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Hierarchical levels


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AEG-Telefunken Logistat CP80


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Hierarchical levels

Level 1 Process Level

Level 2 Unit Control Level

Level 3 Group Control Level Level 4 Process Control Level

Level 5 Operation Control Level


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DCS Hierarchy Structure


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b


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DCS Sub-system


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Main sub systems of DCS

Field stations

Presentation and monitoring devices

Communication units


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PROCONTROL Local field station


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Local Field Station

Smallest intelligent unit of the DCS is themulti-loop control in the field attached tomany local controllers.

Honey well TDC 3000 field station is known ascontroller file

Siemens TELEPARM field stations are known a

Automation subsystem BBC PROCONTROL Field station is known as

Compact processing station


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Field station

Field station usually consists of

1. A microcomputer with

32 to 64Kb RAM

16 to 32 analog inputs8 to 16 analog outputs

upto 48 digital I/Os

a serial and parallel bus interface

2. Hard copy output terminal

3. Local display terminal


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Library of functions

Inputing signals

Input signal conditioning

Signal and hardware testing

Limit values and trends check

Alarming Reporting and logging

Mathematical and logical signal processing

On-line and off-line signal processing

Visual display and printing

Output signal conditioning

Signal outputting


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Presentation and monitoring devices

On the display screen the following will be

usually represented

Current values of measuring data

Positions of actuators

Logs of the plant

History of individual signals

State of different plant parts, control loops, etc.


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The information displayed on the screen can

be generally classified as follows:

Plant overview;

Group overview;

Local multi-loop representation of individual

process variables reporting and logging

Representation of secondary plant data (statistical parameters, etc.)


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TDC 3000 displays

TDC 3000 displays are used in three operating

modes:

Normal conditions

At time of process upset

In the event of control equipment malfunction


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Normal condition displays


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Overview display


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Schematic display


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Group display


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Group display with trends


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Trend curve updating


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Group display with hourly average


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Detail display


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Trend overview display


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Batch/sequence operation display


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Batch summary display


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Batch display


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Process upset displays

Alarm annunciator display


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Area and unit alarm display


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Process management system display


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Communication options in DCS

The communication system also follows hierarchy system For short distance applications star network is applicable

At level 1 usually point-to-point connection is applicable toconnect individual sensors and actuators to analog and

digital inputs and output of the field station. For shorter distances instrumentation bus like IEEE 488, or

special bus like k-110 of AEG Telefunken can be used.

For level 2 and 3 long distance buses like IEEE 488, PDVBUS , PROWAY, etc which are extendable upto 5 to 10kms

are used. Generally long distance buses are serial buses.


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Field bus communication


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Step 1: Configuration of operating system

Composition of groups and overview displays

Period for trend displays

Hi-way station priorities

Message tables


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Step 2: Configuration of controller functions


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Some popular DCS

Leeds and Northup Max-1 System


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Leeds and Northup Max-1 System


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Control Bailey Micro-Z System

H ll TDC 2000 TDC 3000


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Honeywell TDC-2000, TDC 3000

system


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TDC 3000 system architecture

The basic modules are;

Controller file

Operator station

Hiway traffic director(HTD)

Analog unit

Process interface unit


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Honeywell TPS system


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TPS Honeywell

The basic components of TPS system are:

Global user station (GUS)

Total plant desktop module

Total plant engineering tools

Total plant history module

Advanced application software packages like total

plant batch control, multivariable control,optimization, etc.


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Echelons Lonwork System

The basic building blocks of Lonworks are

Neuron chips

Lontalk communication protocol

Lonworks transceivers

Network management services


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Lonwork System


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Features of DCS


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Advantages of DCS

3.distributed_control_systems.pptx

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