Automated Control Systems

ADO.NET is data access technology it is evolution from DAO to RDO to ADO

DAO- Data Access Objects
RDO-Remote Data Object
ADO-ActiveX Data Objects
ADO.NET-Not an acronym
ADO.NET Features
•ADO.NET supports both connected and disconnected solution
•It has tight integration with XML and .Net Framework
•HTTP is used to transport XML between layers
•ADO.NET is managed library of code and has same rules as managed library Connected Layer
•In this our base code will explicitly connected with a data base, the connection is explicitly opened and closed
•It is achieved using Data Reader objects to get records from data store using forward-only, read-only approach

Disconnected Layer
•The disconnected layer is achieved using Dataset. Dataset is local copy of any number of related data tables
•Once the user gets Dataset object it is completely disconnected from the DBMS
•the connection is opened and closed automatically on our behalf
•Data adapter objects are used to fill a Data set with Data Table
•Using Dataset the client tier is able to update and modify its contents of data source while it is disconnected, and it can submit the modified data back using related data adapter
•The main advantage of this layer is data is manipulated without incurring the network traffic

The control concept of control systems also applies to Thermal power.  In that way, there are certain ways in which the thermal power plant is to be controlled

1. Controlling the power generated

First, the power generated needs to be controlled in MW (megawatt). It is not possible to store power. Therefore, the power depends on load on the grid. The load/generation decides the frequency of the grid which is actually controlled by the turbine. The voltage is controlled by the generator and the frequency is controlled by the grid

2. Controlling the steam flow

The power generated directly depends on the steam flow. Turbine valves are throttled (mechanism which restricts the speed or the power of engines) to control the steam flow

3. Controlling steam pressure

Controlling steam pressure depends on the steam flow. The amount of the steam flow decides its pressure. More flow increases the pressure and less flow decreases

4. Need to control the fuel/Air inputs to the boiler

There is a necessity to control the fuel or the air inputs to the boiler (a device that generates steam)

5. Need to control feed water flow to boiler

With “Supervisory Control” primary loop control is returned to analog controllers, while computer monitors the process & adjusts the set points. Computer is relieved from computational tasks & can be utilized for process optimization & plant management

In a Supervisory Control System, Analog control subsystem& panel instrumentation is used for controlling but it is interfaced to a Supervisory Control Computer through interfacing hardware. This Supervisory Control computer provides the facility for monitoring process (which provides the process mimics on the video display units for operators with features like Alarm Handling, Data Storage)

Drawbacks

• Extensive wiring between analog controllers & other instrumentation to the computer system
• Interfacing Multiple Vendor sub-system-Interfacing one vendors computer system to another vendors analog instrumentation
• Costly than DDC

Hierarchical Computer control System

• A hierarchical system is network of process and/or information management computer systems integrated to serve a common functions like management and control of large refineries, pipeline network, energy production facilities for whole country
• Information passed from primary level of process monitoring & control, up through supervisory levels, to decision making/top management level & vice versa
• With hierarchical systems, primary computers provide direct control of process & can be DDC, supervisory or microprocessor base

Drawbacks

• De-centralized control But not centralized & de-centralized control
• Impractical redundancy

To provide a safe shutdown of the system or tripping of equipment, when the operating constraints are violated. The requirements are availability and integrity. Dual redundant, triple redundant or quadruple redundant systems are available. Features like memory test, self test, functionality test are done routinely to test the integrity of the system

Protection in power plant – overview

• Plant Level
• Subsystem Level

1. Boiler Safety
2. BMS – Burner Management System – Guided by NFPA guidelines
3. Interlocks and Protection for Mills
4. EMS – Electromagnetic Safety Valves

• Turbine and Generator Protection

1. Over-Speed
2. Low Vacuum
3. Low LO pressure
4. Steam temp. Trips
5. Seal oil/H2 Diff Pressure
6. Electrical Trips of Generator

• Shutdown Sequences
• Individual Equipment Level

1. ID Fans
2. FD Fans
3. PA Fans
4. Mills
5. BFP
6. CEP etc.,

Alarm systems

• Alarm System – alerts the operator about a trend towards a operating constraint.
• Alarm Management – Very important – provide Alarm priority, Grouping and action plan for each alarm.
• Types

Standalone

• Hardware based
• Software base

Integrated

Alarm Sequences & Standards

• Normal Sequence
• Ring-Back Sequence
• First- Up Sequence

Power plants are controlled by control systems which provide a manual and automatic control of plant

• Maintain an adequate margin from safety and operational constraints – Control System
• Monitor these margins and plant conditions and provide immediate indications and records – Indications, Recording and historization
• Draw the attention of the operator by an Alarm System to any unacceptable reduction in the margins – Alarming
• Shutdown the plant, if Operating Constraint is violated – Safety and Shutdown system

Types of controls

• Analog Control –  Controls a particular parameter as per Set point

• Binary Control

1. Sequence Control – For Startup and Shutdown
2. Motor Control – For Motor Operated Devices

• Permissive
• Interlocks
• Protection

• Protection System – Trips the system

Control Islands in Conventional TPP

• Boiler
• Steam Turbine
• Balance of plant

1. Regenerative system
2. Cooling System
3. Various Auxiliaries

• Misc. Systems

1. Fuel Handling System
2. Ash Handling System
3. Nox Reduction System

Integration of Power Plant Controls

• Co-ordinated Control Mode

1. Integrates Boiler and Turbine Operations
2. Set point received from Unit Load Dispatch Center

• Sliding Pressure Operation for Power Plant

1. Complete control operation by Boiler itself
2. Turbine valves are fully open except for the Pressure Protection

• Integration with Enterprise Level Control – Private Power Bidding

• Integration with Grid level Control

What is DCS ?

Functionally and physically separate automatic process controllers, process monitoring and data logging equipment connected with each other to share relevant information for optimum plant control is called distribution control system

How is DCS ?

• Microprocessor based DCS Systems are a form of DDC that divide data acquisition & control functions among a number of independently operating microprocessor controllers. The controllers are linked together with a data highway that is routed through the plant & connected to the operators console in the control building
• Basically DCS is task partitioning, the breaking up of duties of mainframe computer into many smaller tasks distributed throughout the system
• DCS can be called a computer, but it is no longer a single mainframe.  Instead, many small computers are distributed throughout the remote area installations, sharing the work that the mainframe had to do alone. In fact, even if central station facilities breakdown, remote control operation will continue without interruption

Why DCS ?

• Dominates drawbacks of DDC, Supervisory & Computer control system
• Cost: costless as compared to features they provide
• Versatility: Process plant control, Start-Up, Shutdown & Multifunction capability (Logic, sequence, loop controller, data logger etc.).Used for advanced control, optimization, management level
• Expandability: Handles hundreds of IOs & Used in number of industrial process control application
• Flexibility : Supports new technologies

Nowadays DCS is nothing but Distributed computer control System

Avionics

It is science and technology of electronic systems and devices for aeronautics and astronautics

The electronics used for piloting an aircraft are called avionics

Avionics mainly consists of

• communications and navigation systems,
• Autopilots
• Flight management system(FMS)

Navigation :

• Absolute Navigation Systems that measure the state vector without regard to the path traveled by the vehicle in the past:
• Dead Reckoning Navigation Systems that derive their state vector from  a continuous series of measurements beginning at known initial position.
• Mapping Navigation Systems compares the images of the ground, profiles of altitude, sequence of turns, or external features comparing observations to a stored database.

Communication :

Intercom among crew and external two way voice and data links

Flight Control:

Stability Augmentation and Autopilot, the first points the airframe and controls its oscillations, while the latter provides such functions as attitude-hold, heading-hold, and altitude hold. Flaps, slats, and spoilers are often controlled electronically in addition to rudder, elevator and ailerons.

Engine Control: Electronic control of the engine thrust, often called throttle management. Flight

Management: FMS stores the coordinates of the route way points and calculates the steering signals to fly towards them. It calculates the climb and descent profiles that may be followed with or without constraints on the time at which the designated fixes and altitudes are crossed

Subsystem monitoring and Control: Faults in all subsystems are displayed, as are recommended actions to be taken. This subsystem includes wired logic and software for automatic reconfiguration of faults in critical subsystems

Collision Avoidance: This subsystem predicts impending collisions with other aircraft or the ground and recommends an avoidance maneuver.

• Weather detection: This subsystem observes weather ahead of the aircraft so that the route of flight can be altered to avoid thunder storms and areas of high wind shear.

YEAR PRODUCT

1900-1908    : Manual control with gauge and valves

1938-1940     : Pneumatic signal and instruments

1950’s              : Electronic signal and instruments

1960’s              : Computer starts to be used.(1962: Introduction of direct digital control)

1968                 : PLC arrived on scene (G.M.USA)

1969                 : First PLC manufactured for automotive industry as electronic equivalent to relays

1970                 : First application of PLC outside automotive industry

1972                 : Introduction to distributed control and PID control

1973                 : Introduction of “smart“ PLCs for arithmetic operations printer control, data move, CRT operation

1974                 : Honeywell, U.S.A. announces its first DCS TDC 2000

1975                 : First use of DCS in hierarchical configurations

1980                 : Introduction of intelligent I/O modules to provide higher speed and accuracy

1982                 : Honeywell introduces large DCS with smart MMI software techniques, TDC 3000

1984-1985     : Communication come to the forefront MAP, TOP

1985                 : SCADA Software for HMI/MMI for IBM PC coupled to panel mounted controller

1986                 : Unix Operating System and Computer Buses

1887                : DCS uses satellite to control remote plant from one control room

1990                : Windows 3.0 and X Windows

1992                : Third party interface in DCS

1995                : Windows NT/95(32-bit word)

1998                : Use of Java(internet technologies), Visual Basic

2001-02        : Use of XML, .NET technologies in DCS/PLC software’s

Fire Panel

It is the hardware that controls fire sensors and other peripherals

Fire Panel Should

• Be able to sense fire.
• Have some means to alert the concerned person.
• Be ready to operate.
• Be easily maintainable

Components Used

Detector

Detector is essentially a fire sensor. Conventional detector is a non-addressable detector whereas intelligent detector is addressable.

Module

Module is a general purpose switch. It can be input point or output. Input point is called as monitor module. The output module is called as control module. These are meant to interface external devices with the fire panel.

Alarm

Event generated by the system which gives the indication of the fire.

Point

The smallest addressable entity in the system. Detectors, modules etc are points. System capacity is often measured in terms of the number of points

Fire Alarm Control Panel

SLC Loop

The circuit in which the majority of the sensors and other devices are connected. Loop could support 100-150 detectors and equal number of modules.

Networking

The panels can be networked with their proprietary protocol. The panels can communicate with one another.

Add-on Devices

Which add more points to the system like SLC, but with a different physical connection.

Anunciator Devices

Which are meant to announce the alarm or trouble conditions in location different than the panel.

Access control is devices which answers for the questions like who, when, where

Control Cards Technology

• Magnetic Stripe
• Barcode
• Barium Ferrite
• Wiegand
• Proximity
• Keypads
• Card/Keypad Combos
• Biometrics
• Smart Cards

Magnetic Stripe

• Four tracks
• An exposed read head is placed in the reader used to read the Cards

Barcode

• Card is swept through a reader
• The reader captures a picture of the thickness of the  bars and the space between bars

Barium Ferrite

• Thin sheets of magnetic material are embedded between the layers of a card to give each card a unique number

Weigand

• Special alloy wire is used to create two distinct magnetic regions in a single piece of wire when it is passed over a magnetic field
• A wire is embedded inside the card in a specific order to create an unique code

Proximity

• Reader transmits an Radio Frequency signal that powers the card
• Card retransmit its data to the reader when the host system reads it

Keypads

• Multi-digit number is entered to gain access

Card/Keypad Combinations

• Keypad number must be entered after card is presented
• Each card is assigned a PIN number

Biometrics

• Reads a property of the body

-          Retina

-          Voice match

-          Finger print

Smart cards

• Special chip technology to receive/store data

-          Contact – chip is touched by wires to transmit data

-          Contactless – data is transferred via RF much like proximity