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Copyright © SEL 2011
Communications –
Basic
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Overview
• Serial Communications
• Ethernet
• Fiber-Optic
• SCADA Protocols
• Peer-to-Peer Protocols
• Ethernet Protocols
• Comm Architectures
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Communications Architectures
Serial Network
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Serial Communications
Serial is the simplest form of communication
between two devices
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Serial Standards
• RS–232
• EIA–485
• Universal Serial Bus (USB)
• RS–422
• G.703
• Many others…
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Serial Standards
• RS–232
• EIA–485
• Universal Serial Bus (USB)
• RS–422
• G.703
• Many others…
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So What is RS–232?
RS–232 is a ‘Recommended’ Standard by
which two devices communicate♦ General practice recommends distances no
greater than 50 feet over copper media
♦ Standard does not define protocol, only physicalinterface functionality
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RS–232 Wiring
• The original RS–232 specification denotes
usage of a 25 pin cable• Modern RS-232 devices use DB9, including
SEL serial products
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RS-232 Flow Control (Handshaking)
• Software (XON / XOFF)
• Hardware (RTS / CTS)
• Important to consider when transmissionmedium can require careful timing (wireless
radios)
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RS-232 Connector Types
Two different connectors are associated with
two major types of hardware♦ Data Terminal Equipment, or DTE; SEL relays,
meters (IEDs, in general) etc. are DTE
♦ Data Communications Equipment or DCE; SELcommunications devices such as transceivers,media converters, etc. can be DTE or DCE
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RS-232 Connector Types (cont)
• DTE will transmit on pin 2 and receive on pin
3• DCE will transmit on pin 3, and receive on
pin 2
• Null modem allows DTE-DTE or DCE-DCEcomms
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RS–232 DB9 Pin-Out (DTE)
DB–9M Function Abbreviation
Pin #1 Data Carrier Detect CD
Pin #2 Receive Data RD or RX or RXD
Pin #3 Transmitted Data TD or TX or TXD
Pin #4 Data Terminal Ready DTR
Pin #5 Signal Ground GND
Pin #6 Data Set Ready DSR
Pin #7 Request To Send RTS
Pin #8 Clear To Send CTS
Pin #9 Ring Indicator RI
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RS–232 DB9 Pin-Out (DCE)
DB–9M Function Abbreviation
Pin #1 Data Carrier Detect CD
Pin #2 Transmitted Data TD or TX or TXD
Pin #3 Receive Data RD or RX or RXD
Pin #4 Data Terminal Ready DTR
Pin #5 Signal Ground GND
Pin #6 Data Set Ready DSR
Pin #7 Clear To Send CTS
Pin #8 Request To Send RTS
Pin #9 Ring Indicator RI
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“ SEL IED” RS-232 DB9 Pin-Out
(DTE connector)
DB–9M Function Abbreviation
Pin #1 5 Vdc n/a
Pin #2 Receive Data RD or RX or RXD
Pin #3 Transmitted Data TD or TX or TXD
Pin #4 + IRIG–B n/a
Pin #5 Signal Ground GND
Pin #6 - IRIG–B n/a
Pin #7 Request To Send RTS
Pin #8 Clear To Send CTS
Pin #9 Shield n/a
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DTE->DCE Communications
• In serial cable terms, a “straight-thru” cable
is used• ‘C285’ cable w/ 2 x DB9-M ends
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DTE->DTE Communications
• In serial cable terms, a “null-modem” cable
is used• ‘C273A’ cable w/ 2 x DB9-M ends
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Transmitting Data – How does it
work?
• RS–232 communication is dependent on a
set timing speed at which both pieces ofhardware communicate
• The hardware knows how long a bit shouldbe high or low
• RS–232 also specifies the use of “start” and
“stop” bits
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To Talk the Talk…
• Both devices must have the same data rate
to communicate, but they must also know tohandle problems
• Baud rate is the number of changes in thesignal per second, also known as bits persecond, or bps
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Common Serial Settings
Most serial communications port settings areread in the following form:
♦ Bits per second (baud, or speed)
♦ Number of data bits
♦ Parity
♦ Number of Stop bits
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Speed Limitations
• All serial devices have
an “UART” controller • SEL devices are
typically limited to 57600
baud• Older SEL products may
be limited to 38400, or
even 9600 baud
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What is RS–485?
Communications interface using a ‘balanced’
or differential signal process to supportpoint–to–point, point–to–multi–point, andmultiple drop applications
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Physical Media: Twisted Pair
Network Topology:Point-to-point, Multi-dropped, Multi-point
Maximum Devices: 32 drivers/receivers
Maximum Distance: 4000 feet
Mode of Operation: Differential
Maximum Baud: 100 kbit/s - 10 Mbit/sVoltage Levels: -7 V to +12 V
RS–485 Specifications
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RS-485 Has Better Noise Immunity
Opposing polarities
and twisted pairconductors fortransmit and receive
signals providesimmunity to
magnetically–
induced noise
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RS–232 vs. RS–485
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RS–485 Full–Duplex
• “4-Wire” Standard
• All device connections are consistent• Only first and last devices in chain connect the
reference wire
• Required for SEL point–to–point or LMD protocols
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RS–485 Half–Duplex
• “2-Wire” Standard
• Only one device can talk at a time• Rx and Tx matching polarities are tied together (+
to + and - to -)
• Does not support SEL protocols
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RS–485 Half–Duplex
• Half-Duplex Comms imply that receive/transmit beaccomplished on same data lines.
• Two methods to switch rx/tx mode:
♦ - RTS Line “High” on 232 Connector (HW+SW)
♦ - “SDC” – Send Data Control (SW-only)
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RS–485 Termination Resistors
• Used to match impedance of 485 TX node tocommunication cabling in use.
• If mismatch is in place, portion of messagereflected back at transmitter, data is truncated.
• Connect +/- (or A/B) pairs of Transmitter /Receiver, only at extreme ends of network
• Use resistors in range of 120-150 ohms.
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Serial
Physical media
Copper Fiber optics
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Fiber-Optic Serial
• Dual-Transceivers encode serial data over fiber-optic links
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Universal Serial Bus (“ USB” )
• Developed as open standard for interconnectionof computing peripheral devices.
• Software Drivers required to determine behaviorof USB connection.
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USB/RS232 Converters
• Connect a PC with no physical RS232 ports tolegacy IEDs.
• SEL Solution = C662
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Network Communications
• OSI Model
• Physical media♦ copper/twisted pair
♦ fiber optics
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Network Communications
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What is a ‘Network’?
A collection of two or more elements linked
together for the purposes of sharinginformation, resources, etc.
♦ ARPANET was the world’s first ‘packet
switching’ network
♦ ARPANET successfully passed the firstcommunication packets in 1969
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Jump Forward 40+ Years…
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The (OSI) Reference Model
Layer Function
Layer 7 Application Interface between NOS
and user’s applicationsoftware
Layer 6Presentation
Data representation
Layer 5 Session Name to address translation,access security
Layer 4 Transport Reliability of transmissionfrom end to end
Layer 3 Network End-to-end addressing(specific to the protocol)
Layer 2 Data Link Media access and addressing(on the same physical wire)
Layer 1 Physical Cables, connectors, wires and
signaling issues
Application Data
Wire/Fiber
• Top 3 layers areapplication-oriented
• Responsible forpresenting theapplication to the user
• Unaware of how dataget to the application
• Lower 4 layers dealwith packaging &delivery of data
• How it is transmitted
• How it is reliably
received
• How it is routed
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OSI Stack and Ethernet
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Ethernet
• Establishes direct connection betweensender and receiver
• Based on MAC (Layer 2) address
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MAC Address
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Ethernet Devices - Hubs
Hub: Simple Muxing Device That Redistributes
all Data that it Receives to all Connections• Physical Layer
• Lowest cost• Effectively Obsolete (tough to buy new)
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Ethernet Devices - Switches
Switch: Intelligent Muxing Device Monitors
and Redistributes Data to AppropriateConnections; will not Redistribute DetectedBad Data
• Uses Data Link layer (MAC address filtering)
• Additional functions in ‘Managed’ switches
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Ethernet Devices - Switches
• Can be used to interconnect differentEthernet cabling mediums (Copper, Fiber,
etc)
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Ethernet Devices – Managed Switches
• Advanced Functions provided by managedswitches include:
♦ Port security (disabling, VLAN, priority)
♦ Network Monitoring (SNMP, web interface)
♦ Redundant (ring-style) networking (RSTP)
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Ethernet Devices - Routers
Router: Interconnects Two Networks Such as
Substation LAN and Utility WAN• Uses Network Layer/Transport layers
• Commonly used for Network Security• Often contain ‘Firewall’ functions
Eth t M di T
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Ethernet Media Types
• CAT5E / CAT6 Twisted Pair Cable, RJ45Connectors
♦ Most common interface standard, cables arerelatively easy to manufacture.
♦ Cable provides acceptable EMI shield for mostindustrial installations.
♦
Maximum cable limit of 300 ft.♦ 10 Mbit/s through to 1000 Mbit/s (gigabit)
Eth t M di T t
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Ethernet Media Types cont.
• Fiber optic cable, multi-mode (MM) orsingle-mode (SM)
♦ Common in substation installations, due to EMIimmunity.
♦ Maximum lengths of 15km (MM) and 110km(SM)
♦
10 Mbit/s through to 1000Mbit/s (gigabit)
D t P t l
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Data Protocols
P t l Wh t th ?
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Protocols – What are they?
• “A formal, defined set of digital messageformats and rules for exchange of data
messages between computing systems”
• Frequently include signaling, authentication
and error detection/correction capabilities
SCADA Protocols
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SCADA Protocols
• Follow Master/Slave (or Client/Server)relationship
• SEL Protocol
• Modbus
• DNP 3.0
SEL Protocol
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SEL Protocol
• Supported by all SEL IEDs
• Combination of ASCII/Binary data transfermodes.
• Supports auto-configuration of tag data
• Time-stamps supported in target datarange if target is in SER configuration.
SEL Protocol Auto Configuration
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SEL Protocol – Auto Configuration
• “CAS” Command – Return Meter and EventReport Configuration Data
• “DNA X” Command – Return completeindex map of relay word bits
SEL Protocol Fast Op Commands
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SEL Protocol – Fast Op. Commands
• Two main styles of bits can be written toSEL IEDs – Remote Bits (RBs) and
Breaker Bits (BRs)
• Breaker Bits correspond to OC and CC
targets in Relay Logic• Remote Bits typically used for additional
logic.
Serial Protocols Modbus
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Serial Protocols - Modbus
Modbus Protocol
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Modbus Protocol
• Referred to as “Modbus/RTU”
• Developed by Modicon for their PLCs• Simple Protocol Used in Many RTUs,
PLCs, and Other IEDs
• Compatible w/ RS-232 and 485
Modbus Register Mapping
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Modbus Register Mapping
• Register map defined by manufacturer
• Hard-coded and configurable map arepossible
• All boolean data types are single-bit
registers
• Holding and Input registers are 16-bit
Modicon Addressing
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Modicon Addressing
• Modicon Addressing
• 0X Discrete Output / Coils• 1X Discrete Input
• 3X Input Register• 4X Holding Register
Modbus Message Framing
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Modbus Message Framing
• Data Request and Response
♦ 1 byte Slave address
♦ 1 byte Function code
♦ n bytes Data bytes
♦ 2 bytes CRC-16 block check
Read Coil Status (01h)
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Read Coil Status (01h)
• Reads Status of Various Bits
• Read Up to 1000 Bits per Request• Technically classified as 'Digital Output'
status data type
Read Input Status (02h)
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Read Input Status (02h)
• Read Input Status (02h)
• Identical Operation as Read Coil Status(01h)
• Functionally used as 'Digital Input' data
type
Read Holding Register (03h)
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Read Holding Register (03h)
• Used to Read From Database Directly
• Data Response Is Entire Register • Read up to 125 Registers per Request
Read Input Register (04h)
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ead pu eg s e (0 )
• Functionally identical to Read Holdingregister op-code.
• Many devices will only have a singleregister map and will return the same value
whether op-code 0x03 or 0x04 is used.
Force Single Coil (05h)
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g ( )
• On SEL equipment, Operate Remote andBreaker Bits
• Clear Archive Records
• Hold and Release Copies of Data Records
Preset Single Register (06h)
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g g ( )
• Write 16-bit value (2 Bytes) Directly to aDatabase Register
• Technically corresponds with Input Registerdata map.
Preset Multiple Registers (10h)
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p g ( )
• Write Multiple 16-bit Words of Data toContiguous Database Registers
• Write up to 120 Registers at once
Modbus Error Responses
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p
• 01 - Illegal Function
• 02 - Illegal Data Address
• 03 - Illegal Data Value
• 04 - Failure in Associated Device• 06 - Busy, Rejected Message
Modbus Decoding - Poll
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• Ex: 01 03 00 00 00 10 DA FC
• 01 = Address of Remote Slave IED
• 03 = “Read Holding Reg” Op-Code
• 00 00 = Start a Holding Reg Addr 00• 00 10 = Return 16 x 16-bit Registers
• DA FC = CRC-16 Error Detection
Modbus Decoding - Response
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• Ex: 01 03 20 <DATA> DA FC
• 01 = Address of Remote Slave IED
• 03 = Holding Register Data Type
• 20 = Number of Data Bytes Returned• <DATA> = Raw Holding Register Data
• DA FC = CRC-16 Error Detection
Modbus Protocol Types
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• 4 Distinct Flavors of Modbus
♦ Modbus ASCII
♦ Modbus RTU
♦ Modbus RTU over TCP
♦ Modbus/TCP
Modbus Register-Encoding
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• How to use 16-bit registers for advanceddata?
♦ 16 Packed Boolean statuses
♦ 32-bit Integers
♦ 32-bit Floating Point
Modbus Packed Booleans
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• 16-bit Register is used to store 16individual Bit states:
♦ Given: 0x0A1F = 0000 1010 0001 1111
Bit 0 = IN101 = 1
Bit 5 = IN106 = 0
Bit 15 = IN116 = 0
Modbus 32-bit Integers
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• Combine 2 x 16-bit registers into a single32-bit Register:
♦ Host requests 2 registers, combines into 1.
♦ High and Low 16-bit register (order?)
♦ Signed or unsigned?
♦ Windows “Calculator” is a useful tool.
Modbus 32-bit Floating Point
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• Combine 2 x 16-bit registers into a single32-bit IEEE754 Floating point Register:
♦ Host requests 2 registers, combines into 1.
♦ High and Low 16-bit register (order?)
♦ 32-bit broken down into sign (1 bit), exponent(8 bits) and mantissa (23 bits)
www.binaryconvert.com
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• Free web-site for converting raw binary/hexquantities into formatted data.
DNP3 Protocol
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• Master/Slave (Client/Server)-style Protocol
• Overcomes many limitations of earlierSCADA protocols
• Open standard, free for implementation by
any vendor
DNP3 History
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DNP3 Introduction
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• DNP Intent
♦ Telecontrol
♦ Read / write of database data
♦ SCADA information
SOE (time-stamp retrieval) COS (state-change report)
time synchronization
SBE (select-before-execute)
DNP3 Introduction
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• Event Based
♦ Binary change of state
multiple change detection
SOE
♦ Analog % change
♦ Event classes
♦ Event buffer
DNP3 Introduction
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• Object Based
♦ Data specification
♦ No direct memory access
♦ Object types
value
change
frozen
♦ Additional attributes
DNP3 Reporting Mechanisms
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• A classic example of a Modbus-style pollingrequest
Master requests specific memory area from slave
Slave responds with all data in region
DNP3 Reporting Mechanisms
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• DNP3 can perform a ‘Static’ or ‘Integrity’Poll
Slave responds with all data of type or all Classes
Master requests all data of a type of Class 0
DNP3 Reporting Mechanisms
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• The master process can also utilize classpolling to use Report-By-Exception and
improve performance
Master performs periodic Class
0
poll
for
sync
refresh
Master performs regular Class 1,2,3 poll
Slave responds to Class 0 poll with all data
Slave reports event data
DNP3 Reporting Mechanisms
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• For extremely low-bandwidth connections,unsolicited reporting can be used.
Master performs
occasional
Class 0 poll for sync refresh
Slave reports unsolicited event data
Slave responds to Class 0 poll with all data
DNP3 Reporting Mechanisms
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• Quiescent polling can also be used, where-by the master process never polls for data
and relies entirely on the slave process toreport changes.
Master does not poll
Slave reports unsolicited event data
DNP3 Protocol Benefits
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• Optimized Communication
♦ Event-driven polling
class 0
class 1, 2, 3
♦ Minimum message size
DNP3 Protocol Benefits
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• High Data Integrity
♦ 16-Bit CRC every 16 bytes
♦ Hamming distance of 6
♦ Data link confirmations
♦ Application confirmations
DNP3 Protocol Benefits
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• Structured Evolution
♦ Subset definitions
♦ Object definitions
♦ Standard documentation
♦ Conformance testing♦ User’s group
♦ Technical committee
DNP3 Recent Developments
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• ‘Recent’ is defined as 2000-era
• Ethernet LAN/WAN Support
• Virtual Terminal Applications
• File Transfer Capabilities
DNP3 Protocol Structure
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• DNP Structure
♦ Modified 3 Layer OSI modelApplication
Presentation
Session
Transport
Network
Data Link
Physical
ApplicationData Link
Physical
DNP3 Message Structure
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• Typical DNP3 Message Frame
05 64
DWG: #853_001
DNP3 Message Structure
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• Data-Link Header, every message startswith this.
• 0x0564• Length
• Control Byte• Destination and Source Addresses
• 16-bit CRC
LEN05 64LSB MSB
SOURCE
LSB MSB
CRCDESTINATIONDLC
DNP3 Message Structure
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• Transport and Application Layer includesactual data.
• Transport Header
• Application Header
• Object Header
• Data Block• CRC
APP Header TH CRCDataObject Header
DNP3 Message Structure
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• Application-Layer Object Data
• Object Header
♦ Group
♦ Variation
♦ Qualifier
♦ Range
DataObject Header
DNP3 Message Structure
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• Common Application Layer FunctionCodes:
♦ 01 – Read
♦ 02 – Write
♦ 03 – Select, 04 – Operate, 05-Direct-Operate♦ 23 – Delay Meas, 24 - Record Current Time
♦ 129 – Response
♦ 130 – Unsolicited Response
DNP3 Message Structure
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• Common DNP3 Default Object Types andVariations:
♦ Binary Inputs – Obj 1,2 Var 2
♦ Binary Outputs – Obj 10 Var 2, Obj 12 Var 1
♦ Counters – Obj 20, 22 Var 5
♦ Frozen Counter – Obj 21,23 Var 1
♦ Analog Inputs – Obj 30 Var 4, Obj 32 Var 2
♦ Analog Outputs – Obj 40,41 Var 2♦ Time/Date Objects – Obj 50 Var 1
♦ Class Objects – Obj 60 Var 1,2,3,4
DNP3 Class Data
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• Reports “Change Event” data from an IED
• Q: What does Class 1, 2 and 3 data
represent?
• A: Whatever the IED defines it as!
• Typically: Binary = 1, Analog = 2, Counter =3
DNP3 Static vs. Event Data
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• Static data from Class 0 object poll
♦ “Current” (snapshot) Value
♦ Does not contain timestamp information
• Event data from Class 1,2,3 object poll
♦ “New Value” from IED event buffer
♦ Timestamp is critical component of message.
DNP3 Message Structure - Options
Obj t T O ti l C t
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• Object Type Optional Components
♦ Time-Tag (Change events-only)
♦ Status Flag
Value, Forces, Restart, Online
Point Force (Local or Remote)
Over-Range
DNP3 Message Structure - IIN
IED R ill i l d 2 b t f IIN
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• IED Responses will include 2-bytes of IIN(internal indications) bits.
♦ Device trouble, re-start, in-local, corrupt
♦ Time Sync Required
♦ Class 1, 2 or 3 data available
♦ Event Buffer Overflow
♦ Requested objects are unknown
DNP3 Commands
U “C t l R l O t t Bl k” (CROB)
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• Use “Control Relay Output Block” (CROB)from host to write to Binary Output Index.
• Supported styles of commands:
♦ Pulse On, Pulse Off
♦ Pulse w/ Trip or Close Qualifier
♦ Latch On, Latch Off
DNP3 Commands – IED Interpretation
IED ill h diff t i t t ti f
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• IEDs will have different interpretations ofDNP3 command codes
• Check the device-specific DNP3 appendix
• From SEL-351S-7:
Peer–to–Peer Protocols
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• Serial: Mirrored Bits®
• Network: IEC 61850 GOOSE
SEL MIRRORED BITS Review
Relay-to-Relay Logic Communication
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Relay to Relay Logic Communication
Proprietary
µ Wave
.....
..... .....
.....
Relay 1
DB9 Connectors
AudioRadio
Other
. . .
. . .
Fiber SEL-28xx
Relay 2
Fiber
SEL-28xx
Other
SEL MIRRORED BITS Communications
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• EIA-232 Asynchronous Message (6-O-1)
• 8 Bits of Bidirectional Status or Control
• High Speed – 10 to 20 ms contact xfer time
SEL MIRRORED BITS Communications
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Channel
Interfaces and
Communications
Equipment
Relay 1 Relay 2
RMB1 . . . RMB8RMB1 . . . RMB8
Transmit
Receive
Transmit
Receive
TMB1 . . . TMB8 TMB1 . . . TMB8
Channel
1 2 3 4 5 6 7 81 2 3 4 5 6 7 8
1 2 3 4 5 6 7 81 2 3 4 5 6 7 8
Transmit “ Mirrored” to Receive
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Relay 1 Relay 2
TR ANSM
IT
RECE
IVE
TR ANSM
IT
RECE
IVE
TMB1
TMB2...
TMB8
RMB1
RMB2...
RMB8
TMB1
TMB2...
TMB8
RMB1
RMB2...
RMB8
1
0...0
0
0...0
0
0...0
1
0...0
Communications Media Requirements
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• Full-Duplex Communications
• EIA-232 Serial Port Interface♦ Up to 38400 bps
• Immune to Power System Fault GeneratedTransients
• Acceptable Speed for the Application
Ethernet Protocols
T l t
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• Telnet
• FTP• Web / HTTP
• DNP3 / IP• IEC 61850
(SCADA and real-time)
Telnet Protocol
P id Vi t l “T i l” i
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• Provide Virtual “Terminal” session onremote host
• Command-line session supported
• No built-in authentication
• TCP port 21
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Web / HTTP Protocol
“HyperText Transfer Protocol”
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• “HyperText Transfer Protocol”
• Supports HTML Text-file encodinglanguage that provides formatted datainformation from a server to a client.
• Simple Authentication supported
• TCP port 80
DNP3/IP Protocol
• “DNP3 over IP”
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• DNP3 over IP
• 99.9% Identical to serial SCADA protocol• Differs only in Time-synchronization
function codes and objects used.
• TCP Port 20000
IEC-61850 Protocol(s)
• Vendor neutral
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• Vendor-neutral
• MMS – Classic Client/Server protocol♦ “Tag-Based” Protocol Language
♦ Standardized Naming
• GOOSE – Peer-to-Peer messaging
♦ High-speed data sharing
Communications Architectures
• Star Topology
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• Star Topology
• Bussed/Daisy-Chain Topology
• Ring Topology
• Hybrid Ethernet Topologies
• “Classic” SEL Topology
Star Topology
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Star Topology
• Benefits:
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♦ Flexible for Serial/Ethernet hardware
♦ Independent Data Path to end devices
♦ Quick Concurrent polling of end devices
• Draw-Backs:♦ Additional Comms Cable, More $$$
♦
Occasional use of repeaters required♦ No redundancy
Bussed / Daisy-Chain Topology
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Bussed / Daisy-Chain Topology
• Benefits:
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Benefits:
♦ Inexpensive communications to many devices
(minimal cabling)
• Draw-Backs:
♦ Round-robin polling delays (slow data updates)
♦ Devices must be addressable (no SEL protocol)
♦ No redundancy
Ring Topology
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Ring Topology
• Benefits:
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♦ Less cost of cabling
• Draw-Backs:
♦ Extra Configuration
♦ Some devices do not support (for Ethernet,Managed Switches required)
♦ Proprietary Connections
Hybrid Topologies – Redundant Star
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Hybrid Topologies – Redundant Star*
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Hybrid Topologies – Star/Ring
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Hybrid Ethernet Topologies
• Benefits:
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♦ Redundant, self-healing Architectures
• Draw-Backs:
♦ Extra $$$ for additional cabling/switches
♦ Extra Configuration
♦ Some devices do not support (Managed
Switches generally required)
“ Classic” SEL Topology
• Communications processor concept• SEL-2032 vs. SEL-3530 RTAC
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SEL 2032 vs. SEL 3530 RTAC
• Settings and hardware features
Classic Comm. Processor System
Wireless
Device
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Non-SEL Relay
SEL-2407
GPS Clock
Modem
PC
Local HMISCADA Master
M e t e r i n g
E v e n t s
A l a r m s
C o n t r o l s
T i m e S y n c h r o n i z a t i o n
C o n f i g u r a t i o n
SEL RelaySEL Relay
SEL RelaySEL Relay
Device
SEL-3021
Satellite
SEL-2032
Modern Comm. Processor System
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Questions?