Tim Sawtelle, P.E.Dirigo Engineeringtim@dirigoeng.com(207) 453-2401

SCADA, what can it do for you?

John MurrayControl Point, Inc.

johnmurray@controlpt.com(207) 841-5948

A REVIEW OF THE PURPOSE ANDBASIC FUNCTIONS OFSCADA SYSTEMS FOR

WATER AND WASTEWATER SYSTEMS.

Things to be aware of as you planthe installation or upgrade of

your SCADA system.

SCADA

Definition of SCADA

“Supervisory Control And Data

Acquisition” Computer controlled system that monitors, controls

and records industrial or utility processes. Implications

Supervisory Control Big Picture• set parameters for control• monitor performance

Programable Electronic Controllers Usually involves communication with remote site(s) Data is displayed and recorded on a PC

SCADA System

SCADA Software

SCADA System vs. SCADA Software

SCADA System – The entire system including master station, remotes, instrumentation, communication systems and the SCADA software.

SCADA Software – The software package that normally resides on the primary SCADA PC at the master station.

SCADA Software

Database running on one or more PCs Usually one PC at the master PLC Graphical representation of system Collects and records data and handles alarm

annunciation HMI Functions plus unlimited recording

Data Analog trends, discrete trends/histories Alarm histories SQL or other formats, data can be exported

Statistical Process Control (SPC) information

Internet

(ISP)

SCADA Station

Plant PLC and Remote I/O

Mobile Web Thin Clients

(Web-browser)

Monitor the Process

Manage Events and Alarms

SCADA Software

Tags or Points List of values used in the SCADA system/software

Real world I/O Setpoints Status of Discretes Calculated Values

Totals, etc.

WATERWIZARD

HMI

“Human-Machine Interface”. Displays process data for the operator (M to H) Allows operator access to change/control the process (H

to M)

HMI is usually referring to a keypad/display or touch-screen panel located at a remote site or in the “plant”.

HMI is sometimes used to refer to SCADA Software. An alternative term – Operator Interface Terminal (OIT)

HMI

Telemetry

A system that automatically transmits measurements from remote locations. tele = far metron = measure

Includes: Sensor(s) Transmission/Reception

Radio/Telephone/Network/Cellular Display/Record/Control

RTU

Remote Terminal Unit or Remote Telemetry Unit

A microprocessor controlled device that interfaces with the station or plant. The RTU sometimes controls the local equipment, sometimes includes an OIT/HMI and usually communicates with the master station. Package (integrated) device, proprietary Emphasis on data transmission not programmable

control

RTUs

Typical Remote Site

PLC

Programmable Logic Controller. A microprocessor based device that interfaces with

instruments and equipment at the facility and provides for control and communications. Often is connected to an OIT/HMI Communicates with master Programmable for local/distributed control

Usually uses relay ladder logic• And, or, not, Boolean Statements, math calculations, etc.• If it can be put in words it can probably be put in RLL

Interface with local facility inputs and outputs (I/O) Analog I/O & Discrete I/O

I/O

Field Inputs & Outputs Discrete Inputs (on/off contact closures, relays)

Examples – a pump is running, a float is up, switch position Discrete Outputs (energize a relay coil)

Examples – tell a pump to start, turn on an alarm light Analog Inputs

Examples – flow meter reading, chlorine residual reading Analog Outputs

Examples – send a speed to a VFD, send a SPM signal to a chemical pump

Typical Analog Input

Field Instrument Measures parameter & displays on instrument Produces a DC voltage or current proportional to the

signal 4-20 mA

PLC reads the analog input and converts it to digital real world units for display on OIT and use in local control decisions

Digital value can also to transmitted to master station

Some “words” about PLCs

PLC data storage and communication is measured in “words”. 1 word = 1 numeric value 1 word = 16 statuses

Typical communication with remotes Simple station 1-5 words Complex station 20-50 words Typical radio transmission rate using serial = 600

words/sec.

Communication

Wireless Data Transmission (serial and/or IP) VHF (150 MHz), requires FCC license UHF (450 MHz), requires FCC license 900+ MHz, spread spectrum Cellular Satellite

Wired Data Transmission Phone

leased line or PSTN (dialup) Private Line Network Internet

Wireless Communication

Wireless Communication Components Communication Port & Cabling Radio/Modem

Speed, “words”/minute Transmission System Antenna Path(s) Schedule (polling)

Radio Communications

Store and Forward

#1

#2#3

#4

Cellular Communications

Control Methods

Manual Visual observations, manual switches, manual form ………

Semi-Auto Adjustable Switches & Time Clocks Instruments with control/alarm setpoints Chart Recorders (with setpoints/ relay outputs) ………

Automatic SCADA with programmable control

Local/Distributed Control

To the greatest extent possible individual control decisions are made at the remote site by the PLC Example –transmit tank level to remote station vs.

transmit a request for pump run to remote station Assumes proper design of hydraulic and control system. Need proper interlocks for safety and protection. Automatic procedures at remote with loss of

communication.

Design controls to function as well as possible even if communication is lost.

Emergency/Backup Control

Maintain “manual” operation capability HOA Switches with “Hand” outside PLC Visual feedback; pressure gauge, etc.

Backup controls where possible High/High and/or Low/Low Floats High/High and Low/Low Pressure Switches, etc. Advantages of VFDs

Start and stop gently Short cycles are less problematic

Startup/ Testing

At Startup Ring out all the I/O Test/ prove every procedure

During Operation Be familiar with “normal” operation

What lights are on/off or flashing, etc. Is it acting normal and as you expect it to? Note any unusual operation

Periodically Test critical interlocks/ alarms

License Class Requirements

Is a water or sewer utility with a SCADA system more difficult or complicated to operate than a utility without a SCADA system?

Top 5 SCADA Security Threats per SynergistSCADA

Inability to easily detect anomalous activity

Installing inappropriate applications on critical SCADA host computers

Unauthenticated PLC / Remote Site network connections

The false belief that SCADA systems have the benefit of security through obscurity due to the use of specialized protocols and proprietary interfaces

The belief that SCADA networks are secure because they are not connected to the Internet

SCADA Security Threats

Building and equipment security Entry control, locks, passwords, etc.

Unauthorized employees or former employees Entry control, locks, passwords, etc. Multi-level passwords, etc.

Communications & Network Security

SCADA Security Threats

SCADA Security Threats

The “Isolation” Philosophy Plug into Power & PLC only

No Internet No email No installations allowed No other software No thumb drives, etc. Dedicated backup

SCADA Security Threats

Reasonable approach for semi-obscure systems? Dedicated SCADA PC, no other uses allowed Firewall Internet Security Software Very limited web access, no email reception Send email only from SCADA If use remote access, utilize VPN

Worker Safety

Comply with OSHA, DOL and NEC requirements. Arc Flash, Lockout/Tagout, etc. Utilize panel interface port to eliminate opening

panels for programming.

Variations on the theme

SCADA is a rapidly evolving technology Computer & Software Developments Communications Innovations

We only introduced some of the more common equipment and software possibilities.

There is almost unlimited software choices and add on software products for alarm-notification, reporting and other features.

Also, almost unlimited hardware choices and manuf.

Tim Sawtelle, P.E.Dirigo Engineeringtim@dirigoeng.com(207) 453-2401

SCADA, what can it do for you?

John MurrayControl Point, Inc.

johnmurray@controlpt.com(207) 841-5948