1 www.eit.edu.au Nuts and Bolts of Troubleshooting of SCADA and Data Acquisition Systems by Steve Mackay Dean of Engineering www.eit.edu.au Topics • Background to SCADA • A Simple SCADA & Data Acquisition System • Typical SCADA Communication Structures • Troubleshooting Techniques for SCADA Engineering Institute of Technology (EIT) Troubleshooting of SCADA and Data Acquisition Systems Free Webinar
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1
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Nuts and Bolts of
Troubleshooting of SCADA and
Data Acquisition Systemsby
Steve Mackay Dean of Engineering
www.eit.edu.au
Topics
• Background to SCADA
• A Simple SCADA & Data Acquisition
System
• Typical SCADA Communication Structures
• Troubleshooting Techniques for SCADA
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EIT Micro-Course Series• Every two weeks we present a 35
to 45 minute interactive course
• Practical, useful with Q & A throughout
• PID loop Tuning / Arc Flash Protection, Functional Safety, Troubleshooting conveyors presented so far
• Upcoming: – Electrical Troubleshooting and
much much more…..
• Go to http://www.eit.edu.au/free-courses
• You get the recording and slides
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Background to SCADA
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SCADA
Supervisory Control And Data Acquisition
– SCADA is not just Software or Hardware
– But a complete control system including
communications systems
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SCADASupervisory Control and Data Acquisition
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Remote Terminal Unit
• The complete assembly of equipment at
an end point of the control system in the
field, factory or industrial site.
• This can be a Programmable Logic
Controller (PLC).
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Typical SCADA System
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Local Area Networks
• High speed access
• Ethernet
• Industrial Ethernet
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SCADA Systems Software
10
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Components of a SCADA System
I/ODatabase
RS-232Trend Server TaskReport Server Task
Input / Output Server Task
In InOut
Analog Digital
Out
Instrumentation& Control
DisplayServer #1
DisplayServer #2
Printer
RadioModem
RadioModem
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Key Features• User Interface
• Graphics Displays
• Alarms
• Trends
• RTU (and PLC) Interface
• Scalability
• Access to data
• Database
• Networking
• Fault Tolerance and Redundancy
• Client/Server distributed processing
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SCADA Software Package• Centralized
– Central Control Room
– Distance Between RTU’s and Control Room
• Distributed
– De-Centralized Control
– Multiple Operators
• Proprietary
– Produced by a single company
• Open Standard
– Interoperability
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Client Server for SCADA Systems
Display Node Display Node Display Node Printer
Local Area Network
Server Node
ProgrammableLogic
Controllers
Bridge
I/ODatabase
Databases
Tasks TaskI/O
Alarms
Alarms
Trends
Trends
Reports
DisplayDatabase
Report Display
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Mainframe
Management QualityControl
DisplayClient
DisplayClient
DisplayClient
DisplayClient
AlarmServer
I/OServer
PLC #1 PLC #2 PLC #3
PLC #4 PLC #5 PLC #6
TrendsServer
ReportServer
Bridge
FileServer
Engineering
LAN
LAN
LAN
RadioModem
LAN
RTU#1
RTU#2
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Industrial Communications Protocols
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Topics
• EIA-232 Interface Standard
• EIA-485 Interface Standard
• MODBUS Protocol
• DNP 3.0 Protocol
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RS-232 Connections (DB25)
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RS-232 Breakout Box
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Protocol Analyzer Connections
Protocol
Analyzer
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RS-485 Review
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EIA-485 interface standard
• Distances of up to 1200m
• Data Rates of up to 10Mbps
• 32 Line Drivers
• 32 Line Receivers
NOTE : Total of 32 devices on same line
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• RS-485 Is the Most Common Voltage
Standard in Use Today for Multi-drop
Communication Systems.
• This Is Because …
•It Is Very Resistant to Noise•It Can Send Data at High Speeds
•And Can Go Long Distances
RS 485
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Two Wire Multidrop RS-485
R
R
G
GRX RX
TX TX
A A
B B
A A
B B
GWG GWG
Rt Rt
R
G
RX
TX
A
B
A
B
GWG
R
G
RX
TX
A
B
A
B
GWG
- Generator
- Receiver
- Circuit ground orcircuit common
- Protective ground orframe ground
- Green wire ground orpower system ground
G
R
GWG
Note: The RS-485 standard documentation
leaves out the invertes for the receiver
1200M (4000 FT)
TERMINATION RESISTORS AT BOTH ENDS ONLY
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R
R
G
G
RX RX
TX TX
A A
B B
A A
B B
GWG GWG
Master Slave
Rt
Rt
Rt
Rt
R
G
RX
TX
A
B
A
B
GWG
Slave
R
G
RX
TX
A
B
A
B
GWG
Slave- Generator
- Receiver
- Circuit ground orcircuit common
- Protective ground orframe ground
- Green wire ground orpower system ground
G
R
GWG
1200M (4000 FT)
Note: The RS-485 standard documentation
leaves out the invertes for the receiver
Four Wire Network
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Installation of Bias Resistorsto Minimize Noise
B A560Ω 560Ω120Ω
120Ω
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MODBUS
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Modbus Message Format
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Modbus PLC Notation
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Messages & Functions
• Two types of messages:
– Query/response - specific slave addressd
– Broadcast - address 00, no response required
• Function codes specify:
– what the slave is to do
– what section of the memory map to find or deposit the data
• e.g. Coil Status, Input Status, Input Register,
Holding Register
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What is DNP3?
• Distributed Network Protocol Version 3.0
• Defines communications between:
– Master Stations
– Remote Telemetry Units (RTUs)
– Intelligent Electronic Devices (IEDs)
• More than just communications
• Originally developed in Electrical Utility
Industry
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Designed for SCADA
• Features
– Time stamping
– Optimised use of bandwidth
– Reporting by exception
– Variety of operating modes
• Data Structure
– Analogs
– Binary
– Counters
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Why use DNP3?
• It is an open protocol
• It is optimised for SCADA communications
• It provides interoperability between different vendor’s
equipment
• It is supported by a substantial number of SCADA
equipment manufacturers
• It will provide immediate and long-term benefits to
users
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Features of DNP3• Supports time stamped messages for Sequence of Event (SOE)
recording
• Breaks messages into multiple frames to provide optimum error
control and rapid communication sequences
• Allows peer-peer topology as well as master-slave
• Allows multiple master topology
• Provides user definable objects
• Provides for reporting by exception / event without polling by
master
• Provides for ‘changed data’ only responses
• Broadcast messages
• Secure configuration/file transfers
• Addressing for over 65,000 devices on a single link
• Provides Time synchronisation and time-stamped events
• Data link and application layer confirmation
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Troubleshooting and
Maintenance
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Troubleshooting the telemetry system
• Ensure that components are not removed on line whilst the system is powered up unless the manufacturer specifically indicates that this is permissible.
• Damage to components and modules can occur when removing whilst the system is still powered up.
• Ensure that the antenna system is not disconnected from the system unless a dummy load has been installed, otherwise the radio power amplifier may be damaged.
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The RTU and component modules
Check:
• Analog input modules
• Digital input module
• Interface from RTU to PLC (RS-232 / RS-485)
• Privately owned cable
• Switched telephone line
• Analog or digital data links
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The master sites
• The master sites will generally consist of a more complete telemetry unit and higher quality radio equipment.
• The same troubleshooting techniques can be applied to the master site as are used at the RTUs.
• Additional equipment would include links to other master sites, to the central site and computer control facilities
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The central site
• The operator stations
• The software for the system
• The communications network for the
operator stations
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The operator station and software
There is not much that can be done here if a system fails or has intermittent problems except to systematically replace each connected unit to identify the faulty module
• Operator terminal (normally a personal computer)
• Local area network card(s)
• Bridge unit to radio, microwave or landline system
• Printer connected to operator terminal
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There are however a few problems which
can be examined:
• Operator terminal locks up
intermittently
• Throughput of the operator station and
associated system drops off
dramatically
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Maintenance tasks
• Whether the maintenance tasks are to be
undertaken internally by your company or
outsourced to a maintenance contractor, it
is vital that there is a comprehensive and
planned approach to maintenance
• Tasks should be broken down in to those
things done daily, weekly, monthly and
annually.
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The maintenance unit system
• In industry today there is an increasing
tendency for companies to reduce
permanent staff to cover only the core
business of the company and to contract
out peripheral activities to specialist
maintenance companies.
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Thank You For Your Interest
If you are interested in further training, please visit:
The Engineering Institute of Technologies
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IDC Technologies
www.idc-online.com
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