WWAC2014 DNP3 - Jeff Miller

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DNP3 Implementation

The Do’s and Don’ts

2014 ISA Water / Wastewater and Automatic Controls SymposiumAugust 5-7, 2014 – Orlando, Florida, USA

Speaker:Jeff M. Miller, P.E., ENV SP

2014 ISA WWAC SymposiumAug 5-7, 2014 – Orlando, Florida, USA 2

Presenter

• Jeff M. Miller, P.E., ENV SP– Jeff is a Water Solutions Architect for Schneider Electric’s

Water Wastewater Competency Center.

– Jeff has a B.S. in Electrical Engineering and has workedas an engineering consultant and a control systemsintegrator in the water industry for 24 years.

2014 ISA WWAC SymposiumAug 5-7, 2014 – Orlando, Florida, USA 3

Presentation Outline

• Understanding DNP3

• Planning DNP3

• Executing DNP3

• Summary

How come youdon’t have

comfortableseats like ours?

2014 ISA WWAC SymposiumAug 5-7, 2014 – Orlando, Florida, USA

DNP3

UNDERSTANDING


Understanding DNP3 History

• DNP3 : Distributed Network Protocol– Originally developed by Westronic (now GE) in 1990

– Owned and governed by DNP3 Users Group since 1993

– Widely accepted advanced communications protocol that is…

– A robust and secure protocol over unreliable communications media

– Open to allow interoperability between many different vendorhardware and software solutions

– Efficient for data and application transmission on many types ofmedia and communication frameworks

– Richly featured with built in capabilities preventing the customcoding or configuration needed with other protocols

– A live standard that evolves as technology changes but still allowsbackward compatibility

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Informative References

• www.dnp.org ~ DNP3 Users Group

• www.TriangleMicroWorks.com ~ DNP3 Training

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Understanding DNP3Traditional Polling Protocol Architecture

• Master controlscommunications andprevents collisions

• Data Concentrators may beneeded for repeaters andpossibly for the Master

• Repeaters avoided

• No advanced featureswithout custom programming

– Current data only

– Inefficient, all datatransferred with possibleseparate transmissionsfor different data types

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DataConcentrator

SlaveSlave

Slave

Slave

Slave

Slave

Slave

MasterRadio

Master DataConcentrator

SCADA

– No time stamping

– Little verification ofactions or data quality


Understanding DNP3 ConceptsTerms

• Masters and Outstations

• Static and Event Data

• Routing vs. Data Concentrator

• Reporting ~ one or a combination of the following:– Polling

– Unsolicited

– Unsolicited Report By Exception

– 2-Pass Control

• Classes

• Implementation Levels

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Understanding DNP3 ConceptsKey Concepts

• Static Data = present value

• Event Data = triggered data

• DNP3 Outstations can buffer event data and backfillbetween communication connections

• DNP3 typically has a larger message size– Can transfer multiple data types in single message

– Additional point and message data for quality, security, andconfirmation

• DNP3 includes time stamped data and automatic timesyncing

• DNP3 Masters and Outstations have communicationdatabases that need to be configured

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Understanding DNP3Store and Forward

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100%

0%

50%

TIME

100%

0%

50%

TIME

100%

0%

50%

TIME


Understanding DNP3Polling

• Possible long delaysbetween updates but data is“backfilled’

• Prevents collisions if onlymethod used

• Different data classes maybe polled at different rates

• Infrastructure avoidsrepeaters in architecture

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DataConcentrator

OutstationOutstation

Outstation

Outstation

Outstation

Outstation

Outstation

MasterRadio

SCADAMaster


Understanding DNP3Routing Without a Data Concentrator

• Known as Message Pass-Through or Routing

• Data concentrator may stillbe needed for outstation-to-outstation control

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Outstation


Outstation

Outstation

Outstation

Outstation

Outstation

MasterRadio

SCADAMaster

ROUTING


Understanding DNP3Unsolicited

• Unsolicited messages sentfrom Outstation by time and /or events

• Very efficient but collisionsmay occur on simultaneouscommunications

• Classes determineresponses

• Data may be sent out on astate change or when adeadband is exceeded alongwith a hold time and countvalues to prevent spurioustransmissions

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Outstation


Outstation

Outstation

Outstation

Outstation

Outstation

MasterRadio

SCADAMaster

COLLISION

REPORTED BY EXCEPTION


Understanding DNP3 ConceptsKey Concepts ~ Class

• Class 0: Polled Data– Typically infrequent polls (e.g. daily)

– Typical Data

– Integrity

– Transfer of non crucial stored data

– Run times, etc.

• Classes 1 → 3: Event Data– User configurable by event and response time

– Typically:

– Class 1 immediate unsolicited response (e.g. alarms, controlactions)

– Class 2 delayed unsolicited response (e.g. monitored values)

– Class 3 further delayed unsolicited response (e.g. collected values)

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CLASSES NOT CLASSROOM


Understanding DNP32-Pass Control

• Simple built-in handshake to verify control action andresponse

15

Outstation

MasterRadio

SCADAMaster

OFF ON FAIL


Understanding DNP3 ConceptsImplementation Levels

• Level 1: Typical of simple IED (Intelligent Electronic Device)

– Simple reads and writes, no analog time stamping

– Possible simple unsolicited messages

• Level 2: Typical of small RTU– Supports Level 1 plus

– more types of messages

• Level 3: Typical of large RTU or Data Concentrator– Supports Level 1 & 2 plus

– Fully configurable unsolicited messages by class

• Level 4: Advanced “Smart” RTU– Supports Level 1, 2 & 3 plus

– Additional communication and network options

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Why is DNP3 not used all the timeon Water / Wastewater Implementations?

If I answerthis correctlywill I get free

stuff?

With all theseadvantages I

don’t seewhy it isn’t?


Roadblocks to DNP3 Usage inthe Water / Wastewater Industry

• Started in energy industries

• Mindset of old technologies and designmethodologies

• Not connecting the advanced featureswith application advantages

• Unfamiliar or lack of experience

• Misapplication ~ configuring the old way

• Understanding update rates versesresponse time

• Poor configurations lead to poorperformance and give DNP3 a badreputation

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DNP3

PLANNING


Do’s Don’ts

20

Planning DNP3

• Leverage features to lowersystem infrastructure costs

– Lower antenna heights

– Use of repeaters

• Leverage features to help inthe choosing of communicationmediums

– Fiber, Radio, Ethernet, Cell,Satellite, land line, etc.

• Consider the classes of data indesign

• Understand update ratesverses response times

• Design like a traditional staticdata system

• Dictate a fast response time forall data

• Classify all data as crucial


DNP3

EXECUTING


Do’s Don’ts

22

Executing DNP3

• Plan your data reporting andtake advantages of classes

• Keep network traffic low toavoid collisions

• Leverage features to lowerdata costs on cell or satellitelinks

• Train users to understand thedifference between dataupdate rates and responsetime

• Minimal configuration mayprovide minimal performance

• Assume effort is like otherprotocols you have usedbefore

• Implementation withoutplanning

• Configure for the fastest dataupdate rate possible


Executing DNP3Don’ts ~ Common Configuration Errors

• Too many critical class data points

• Unnecessary data transmitted. Configure only what is needed.

• Hold Time & Hold Count values poorly set– Can cause too much network traffic or can cause too much latency

• Inappropriate or missing deadband & debounce values

• Requesting Confirmation messages at both Application & Data Linklayers is redundant & inefficient

• Confirmation is not required in a Master– Master Writes already require confirmation

– Master Requests require a reply anyway. If no response, retries automaticallyoccur

• Data Link confirmation may be used on very noisy networks, or setFragment Size below 249 bytes and enable Application Layerconfirmation

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Executing DNP3Don’ts ~ Common Configuration Errors

• Data object type buffer sizes improperly set– Too large – wastes limited event buffer space

– Too small – lost events due to buffer overflow

• Multiple Masters can cause poor communications – events will notbe removed from Outstation buffers until all Masters receive

• Poor choice of Network mode – can cause low network efficiency orlatency issues

• Incorrect choice of Operating mode – know when to use Routing(message pass through) or a Data Concentrator

• Understand the implications of choosing Ethernet TCP verses UDP– Ethernet TCP has additional overhead

– Ethernet UDP’s lack of message validation is covered by DNP3 protocol features

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DNP3

SUMMARY


Wisdom and Knowledge

• DNP3 is an advanced protocolthat takes knowledge, planning,and effort to implementsuccessfully

• The cost savings andperformance advantages of DNP3need to be accounted for early inthe design of the network in orderto take advantage of them

• Data must be organized by itsneed and cruciality


Questions?

Jeff M. Miller, PE, ENV SP

Solutions Architect

Water Wastewater Competency Center

8001 Knightdale Blvd.Knightdale, NC 27545-9023Office: 919.266.8360 | Mobile: 919.824.9114JeffM.Miller@Schneider-Electric.comwww.schnedier-electric.com


Bibliographical References

1. "Home - DNP.org - Distributed Network Protocol." Home - DNP.org - DistributedNetwork Protocol. DNP Users Group, n.d. Web. 02 May 2014.

2. Curtis/Woodland Engineering, Ken. A DNP3 Protocol Primer. Calgary, AB, Canada:DNP Users Group, 20 Mar. 2005. PDF.

3. DNP3 Overview. Raleigh, NC, USA: Triangle Microworks, Inc., 22 Feb. 2002. PDF.

4. Aubin, Philip, PEng. DNP3 Communications for Water and Wastewater Applications.Kanata, Ontario, Canada: Schneider Electric, 28 Aug. 2010. PDF.

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WWAC2014 DNP3 - Jeff Miller

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