scada systems for remote monitoring & control of commercial water supply

8/3/2019 Scada Systems for Remote Monitoring & Control of Commercial Water Supply

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- Engr. Paul I. Audu (PAUMA ENGINEERING CONSULTANTS)



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IN THIS PRESENTATION WE SHALL EXAMINE:

- SCADA System & Application- Introduction to Hydraulic Signal Detectors- Components of System Measurements- Digital Transducers

- Typical Site Infrastructures- Application Details



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- In Commercial Water supply system, the primary role of theoperators is to provide continuous service to all consumers with

optimum supply security, quality, and cost.

- There is the need for use of Real-time Control and Supervisory Systems .

- State-of-the-art control and manipulation of physical system

parameters as well as real-time system integration are now possiusing the SCADA systems

- SCADA means Supervisory Control And Data Acquisition systems



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SYSTEM MONITORING AND CONTROL

- It a system of engineering that is involved in real-time

measurement of physical data (Data Acquisition) and translatingthe electrical replica of the physical measurement through real-time communication link to a remote control centre (SupervisoryControl) for effective monitoring and control

- This is achieved via a localised Remote Terminal Unit.

- The hierarchy of such a control system is illustrated in the figurebelow



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This hierarchy is categorised as

follows:

Level 0 - System Hardware

Level 1 - Local Controls(electrical Transducers and RTUs)

Level 2 - Area Controls(man-machine interface)

Level 3 - Supervisory Control



FROM THE PREVIOUS SLIDE IT IS OBVIOUS THAT:

Data acquisition is obtained through ‘hard-

wiring’ with site equipment

Logging, Supervisory Control and Monitoring is

done through Communication Channels e.g.

Microwave Radio Channels, within an RTU (orRemote Terminal Unit).

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When using a SCADA RTU station automation system,the object is that all the information provided on thetwo-way channel can be completely accessed so that

the following centralised remote functions can beimplemented:

- Remote Monitoring

- Remote Control- Remote setting of Protection parameters- Remote Measurement- Event Recording- Monitoring of all Switching devices- Analysis of Fault Recorder data



MALALI PLANT

KADUNA SOUTH

PLANT

RTU

RTU

RTU

RTU

RTURTUTU

RTU

RTU

RTU

RESERVOIR

RESERVOIR

-Flow Cont.

-Level Cont.

-Pressure

-Leak det.

Master Control Center

Booster Station

Lift Station

Line Filter

-Flow Control

-Vol. Control

-Vel. Control

-Pressure Control

-Quality Control-Flow Cont.

-Level Cont.

-Pressure

-Leak det.-Flow Cont.

-Level Cont.

-Pressure-Leak det.

-Vol. Cont.

-Level Det.

-Level Cont.

-Leak det.

-Flow Mon.

-Pressure Mon.

-Leak det.

RTU

-Flow Control

-Vol. Control

-Vel. Control

-Pressure Control

-Quality Control

Lift Station

RTU

-Flow Cont.

-Level Cont.

-Pressure

-Leak det.

RTU

-Flow Cont.-Level Cont.

-Pressure

-Leak det.



The City Water Supply example isa large system with componentsof Inputs and Outputs

The Inputs and Outputs consist of

quantity of water of varying quality and flow into and out of the systemat given pressures.

There are secondary inputs andoutputs, consisting information on

the quality and quantity of water ineach system components withcommand signals for water to bepumped from one component toanother for treatment and fiteration



A typical application is the versatile MOSCAD SCADASystem from MOTOROLA, shown below:



A Typical SCADA system contains the following elements:- Primary Sensors and Control Devices- Remote Terminal Units (RTUs)

- Communication Subsystem- In-plant Control Station

- Central Computer The Primary Sensors and Control Elements will be

determined by the specific installation requirements e.g.Wet well (dry well) – High/Low AlarmsLevel/Flow – High/Low Level, Flow, Pressure measurements Pump Status – Run, Fail, Temperature, Run-time, VibrationPower Monitoring

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- For effective monitoring and control, there is the needfor converting data variable of the Physical System intoa signal whose magnitude and sense are representative

of the data variable.

- Sensing Devices that convert physical phenomenonand chemical composition into electric, pneumatic, orhydraulic output signals known as Transducers are very

useful for this purpose.Two basic categories of transducers are available as follows;

- those based on electric effects - those based on mechanical effects



Fluid Monitoring & Control

- Monitoring and control are mostly implemented at the variouspoints where actuators are applied in the system.

- Modern monitoring is achieved using intelligent instrumentation,and a wide range of measurements are made in measuringinstruments and control systems. The most common are:

- Pressure

- - Temperature- - Flow

- These three forms of measurements account for 90% of allmeasurements made on physical systems.



Other less common measurements that shall be utilised include

PositionVelocity

AccelerationDensityForceWeightLevel

These are effectively utilised in modern transducers that form theprimary data acquisition components in primary systems.



In the design of our measuring instruments, these threecriteria shall, of necessity, be established;

- What is to be measured?

- Why is it to be measured?- What accuracy is required?

These questions are important in establishing aninstrument specification, especially for computer control

schemes in SCADA systems. Figure below illustrates ageneral instrumentation system and the interface withintelligent instrumentation schemes as obtainable inSCADA systems.



Neither instruments nor control systems can have anexistence unless measurements can be made.

There is a wide range of measurands, which are detectedby a wide variety of sensors and are processed by alesser number of transducers.

Measurement of fluid flow involve a long chain of

operations that may involve the process below.

These form the basic principles of techniques that shall beutilised in sensing the measurand (water) characteristicsfor SCADA implementation.

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Flow-rate is sensed by detecting apressure difference across an orifice plate

Pressure is converted to a displacement ina differential pressure cell

Establishment of Pneumatic output

Pneumatic output converted to electricalSignal



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Inductive Pressure (displacement) Transducer



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PRESSUREPressure is a measurand that cannot be measured directly. It isusually measured as follows:

A mechanical device providesdisplacement In response to a pressurechange

This displacement is is translated into

electrical signal by means of displacementtransducer

Electrical signal communicated tocomputer terminal for modern computer

control



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Elastic ElementPressure

Transducer

Mechanical toElectrical

TransducerMechanicalEnergy Output(displacement)

ElectricalEnergy Output

(Voltage orcurrent)

Auxiliaryenergy input

Basic Principle for a Pressure Transducer



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WATER LEVEL

There are many different techniques, some direct (actual measurements)and others indirect (using another measurand). The variety of methods that

provide continuous, automatic signal include:

- Float method- Differential Pressure method- Diaphragm Switch method

- Direct Pressure method- Load Cell method- Capacitive method- Ultrasonic method



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We have looked at measurement of natural phenomena such as flow,pressure, force, level, pH, etc., using analogue variables.

Some of these signals are converted into electrical signals while some

are transmitted as pulses or coded signals.

For these signals to be useful in digital computation, manipulation ofdata associated with natural phenomena is carried out using digitalprocessing.

There is a great effort involved in the translation of analogue signals toa digital format, and there are variety of devices which easily give adigital output in response to natural phenomena.



The following applications are in use:

A digital transducer should measure the natural phenomenon and produce aparallel binary or binary-coded-decimal (BCD) output as shown in figure

7.1(a). This type is known as Direct Digital Encoding and it measuresdisplacement The following applications are in use:

1 The digital transducer shown in figure 7.1(b) operates as Pulse,Frequency and Time Encode r, where a digital pulse train is produced in

response to physical phenomena. Pulse, frequency and time aredependent variables related by:

Time = 1/frequency

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1 The third type shown in figure 7.1(c) is an Analogue to Digital Encoder ,where an analogue effect such as the change in resistance value or thechange in tension on a wire can be operated on by hybrid electronic

circuitry to produce a frequency or pulse train.

2 The last but not the least is the Analogue to Digital Converter , wherean analogue signal from a transducer such as strain gauge orthermocouple can be presented to a digital computer by analogue to

digital conversion. This is illustrated in figure 7.1(d).



DIGITAL FLOW TRANSDUCERS

There are a number of interesting digital techniques in themeasurement of fluid flows. These include:

(a) Transit Time Flowmeters which measure the time differencebetween

transmitting an ultrasonic beam upstream, and downstream across ahomogeneous fluid flow contained in a pipe. This is illustrated below.

Transit Time Flowmeter - 08028451593, 08054143288, 08030723801



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(b) Doppler Flowmeter uses the Doppler effect technique tomeasure

velocity and obtain a corresponding frequency output. The

configuration is shown below:

Doppler Flowmeter



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(c) The Vortex Shedding Flow Transducer uses the principle offlow

diversion or obstruction. If a bluff body is placed in a fluid flow

themoving fluid cannot follow the contours and sheds eddies orvortices. The vortex pattern depends on the bluff body’s shape

andthe fluid’s properties, but the frequency of the vortices depends

on the flow rate of the fluids.



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The photographs of various critical locations requiring measurement forSCADA application are given below;



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FLOW CONTROL

The installation may be a typical insertion type McCrometer (model 282, twoinch full pipe Sensor) for flow measurement shown below:

Sensor for Flow Detection



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TYPICAL DETECTOR INSTALLATION



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LEVEL DETECTORS

For Level detection we are going to utilise the Conductivity SensingTechnology, and in doing this we shall make use of HiTECH’s “Conducti- Probe” , model CP-1 shown below.

The detection level is idealfor

- Pump Control- Run Dry Protection- Overfill Alarm

- Spill/LeakDetection



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Arrangement of a two-level Floatless Controller



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Arrangement of a three-level Floatless Controller



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Equipment Connection for Water

Supply



Various configurations that shall be used for site installations include:

G - Automatic water supply and drainage control

G1 - (a) Automatic water supply and drainage control

(b) Automatic water supply (idling prevention)Automatic water supply (abnormal shortagealarm)

G2 - Automatic water supply and drainage control(abnormal water increase alarm)

G3 - Automatic water supply and drainage control(abnormal filling/shortage alarm)

G4 - Water source level indication, prevention of pump idlingdue to water shortage, automatic water supply control,and indication of water level in tank

scada systems for remote monitoring & control of commercial water supply

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