SCADA, what can it do for you?
Tim Sawtelle, P.E.
Dirigo Engineering
tim@dirigoeng.com
(207) 453-2401
John Murray
Control Point, Inc.
johnmurray@controlpt.com
(207) 841-5948
SCADA
A REVIEW OF THE PURPOSE AND
BASIC FUNCTIONS OF
SCADA SYSTEMS FOR
WATER AND WASTEWATER SYSTEMS.
Things to be aware of as you plan
the installation or upgrade of
your SCADA system.
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
Monitor the Process
SCADA Station
Mobile Web Thin
Clients
Internet
(ISP)
(Web-browser)
Manage Events and Alarms
Plant PLC and Remote I/O
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.

WATER
WIZARD
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)


Discrete Outputs (energize a relay coil)


Examples – tell a pump to start, turn on an alarm light
Analog Inputs


Examples – a pump is running, a float is up, switch position
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
#2
#3
#4
#1
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.
SCADA, what can it do for you?
Tim Sawtelle, P.E.
Dirigo Engineering
tim@dirigoeng.com
(207) 453-2401
John Murray
Control Point, Inc.
johnmurray@controlpt.com
(207) 841-5948