2011 07 iec61850 with as6802 layer2 qos capabilities v4

Copyright © TTTech Computertechnik AG. All rights reserved. www.tttech.com

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ionSubstation Automation with IEC61850:

Adding TDM-style communication with SAE AS6802 Layer-2 QoS for EthernetJuly 30, 2011

Mirko [email protected]


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IEC 61850 and Networks

• Integrate all of the protection, control, measurement, and monitoring functions within a substation

• Reduce wiring, configuration and maintenance costs

• Provide the means for high-speed substation protection applications, interlocking and inter-tripping

• Communication plays key role in integration of Intelligent Electronic Devices (IEDs) and time-critical substationfunctions

Substation is an advanced integrated(netcentric) system


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Substation Definition with IEC61850

Unambiguous description of:• IED capabilities• Relationship between the switchgear (single line) and

the data of the substation automation system• Communication services

… is critical for substation operation and maintenance.


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Network capabilities and communication servicesessential for grid availability(!):

• Deterministic operation under different faults, loads and securitybreaches

• Robust partitioning of bandwidth among integrated control and protection functions

• Prevention of fault propagation among functions bytemporal/functional interdependncies

GOOSE is used for time-critical communication in substation protection applications (sampled/periodic and event-driven communication), via VLAN and QoS guarantees at Layer 2


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Is VLAN good enough to satisfy all substation designchallenges?Is network performance testable enough to preventtransient gliches or rare failures?What happens if the network is suddenly overloaded(fault, DoS attack)?How much testing is viable/enough to ensure reliableperformance?What happens with network performance if we go to 1Gbit/s?Impact of network capabilities on distributed applicationdevelopment and integration?


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SAE AS6802 Time-Triggered Ethernet


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SAE AS6802 "Time-Triggered Ethernet":A Layer 2 QoS Enhancement

Time-triggered extensions on top of standard switched Gigabit-Ethernet

• Synchronous startup

• Synch recovery

• Robust fault-tolerantdistributed clock

Makes Ethernet viable for any criticalembedded system application


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AS6802 and Ethernet Protocols

Distributed control applications and protectionfunctions can use different means of communication!

Ethernet 802.3

SAE AS6802Services

UDP, TCP, ...

Rate-Constrained Traffic (RC)

Best-EffortTraffic (BE)

Time-TriggeredTraffic (TT)

IPIP

UDP, TCP, ...

Rate-ConstrainedServices

Data

Data

Data


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Capability: Ethernet Trafficwith Fixed Latency and µs-JitterFull control of timing/jitter in a system(synchronization of end systems) unaffected by workload


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Capability: Synchronous & AsynchronousEthernet CommunicationSynchronous multicast traffic (protection, critical control functions) cannot be affected by asynchronous Ethernet traffic

Highly robust in comparison to VLAN/Priority-based traffic (green)


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GOOSE: Can operate via priority-basedVLAN or SAE AS6802 virtual links …

With SAE AS6802, GOOSE delivers signal data and operates in completely overloaded multi-hop networkwith defined QoS, µs-jitter and fixed latency

• 0x88B8 (IEC 61850 GOOSE) can be delivered either via VLAN/multicasting -or- via synchronous time-triggered frames (virtual links - VLs)

• Virtual Links extension complementary (+backward compatible) to IEC61850

Data

Data

ProtectionD

ata

Control &

ProtectionD

ata


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Design of reliable substation systems withAS6802

Challenge: VLAN operation depends on failurescenarios and bandwidth use

• Statistical multiplexing with prioritization does not guarantee communicationperformance (but it works in most cases)

• Critical controls in by-wire systems in other industries (e.g., aerospace) do not use VLANs and do not rely on IEEE1588

Guaranteed end-to-end QoS for critical control loopsSimplifies substation design and testing

• Communication perfomance known at design time

• Upgrades and updates of controls do not influence already tested substationprotection performance

Critical protection function cannot be influenced fromoutside (security!)


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Impact on Integrated Protection & Controls

• Reduction in software/system design and verification complexity and lifecycle costs

• what if we design, add new or modify existing functions using different communication apporaches?

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Copyright © TTTech Computertechnik AG. All rights reserved.

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AS6802 Operation Principle


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Time-Triggered Services in SAE AS6802

Time-Triggered Ethernet (SAE AS6802) services add:• Distributed fault-tolerant synchronization

• Continuous time service in case of multiple system faults; no master clock; formally verified

• Synchronous hard real-time communication (audio/video/hard RT controls)

• TDMA-style bandwidth partitioning• Enables parallel low-latency/lossless/hard RT and standard LAN applications in one network


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All nodes are synchronized using a robust global time base

How does Deterministic Ethernet with AS6802 work?


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AS6802 System Synchronization

Synchronization without GPS or "wall-clock" distribution (Distributed Fault-Tolerant Clock)

• Synchronization by executing distributed fault-tolerant algorithm for alignmentof local clocks within prescribed precision time

• Zero fail-over time in case of master clock loss• Continuous time available with multiple faults

• Helps to avoid synchronization instability

• Can be used as backup function for reliable synchronous operation, even ifIEEE1588 or GPS fail


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Switch

TT TTTT TT TTTT TT

3ms cycle

2ms cycle

3ms cycle 3ms cycle

2ms cycle 2ms cycle 2ms cycle

6ms cluster cycle

RC BE BE BE RC BE t

TT TT TT


BE BE BE t

TT TT TT


BE BE RC BE

t

Sender 1

Sender 2

Receiver


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TTEthernet Technology Services (I)

Sync

hron

ous

(TT)

Tra

ffic

Rat

e-C

onst

rain

ed

(RC

) Tra

ffic

IEEE

AVB

/DC

BA

RIN

C66

4IE

EE1

588

Bes

t-Effo

rt (B

E)

Ethe

rnet

Tra

ffic

TTEthernet integrates time-triggered, rate-constrained(streaming) and standard Ethernet best effort traffic


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Certifiable Ethernet Switches

D

C

A

B

1234

ABCD

IndustrialIEC 61508SIL

AutomotiveISO 26262ASIL

AerospaceDO254DO178B

10-7

10-5

10-9

10-6

10-8

Failu

rera

te (p

er h

our)

TTEthernet (AS6802) addresses a broad variety of Real-Time and Safety-Related Applications


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Deterministic Unified Ethernet with SAE AS6802


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Network capabilities impact architectureand application design

• the number of ECUs, wiring and weight

• use of network bandwidthand computing resources

• level of functional integration

• system and application complexity• cost of SW/HW design and integration

• maintenance, reuse and upgrades

• obsolescence management

Deterministic Networking & Platforms forAdvanced Integrated Systems


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QoS for Critical Networks & Systems

• Our products and technologies enable:• Deterministic unified Ethernet networking for fault-tolerant systems with FT

distributed clock, robust partitioning, fault isolation and quick recovery

• Ethernet capable of end-to-end connectivity with precise control of timing and QoS for mixed traffic („white channel“ with well understood behavior!)

• Enhances design of "flat" Ethernet-based architectures and virtualizedenvironments hosting critical and non-critical applications

• TTTech brings proven experience in critical (by-wire) embedded systemdesign and methodology


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By-wire Integrated Modular Architectures: Deterministic Unified Ethernet Network

The network is a hard real-time distributed fault-tolerant computer

• … with efficient partitioning of computing and networking resources

• Key enabler: TDMA network capability

• … to enable hosting of distributedmixed criticality functions

• Different traffic classes supported • Hard RT for any distributed function is viable


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By-wire Integrated Modular Architectures: Deterministic Unified Ethernet Network

Virtualization of computing and networkingresources for critical infrastructure

• Critical distributed applications are not affected by other less critical distributed functions, independent of the system workload

• Can be seen as robust cloud slicing, potentially applicable in enterpriseand smart grid applications


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Closed control loops and end-to-endQoS/Determinism in Smart Grid?


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www.tttech-automotive.com

2011 07 iec61850 with as6802 layer2 qos capabilities v4

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