iec 61850 process bus

8/10/2019 IEC 61850 Process Bus

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IEC 61850 Process Bus


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Scope

IEDs for Process Bus Page 26


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Digital Substations In Context

On-Line Stability

Smart Dispatch

Management of Renewables

Demand Response

Management

On-Line Asset Management

Extended IEC 61850 Interfaces

Advanced Sbstation User Interface

1Gbit/s Ethernet

Cyber & Physical Security

Wide Area Protection & Control

Substation State Estimation

Digital NCIT & Substation

Equipments

VSC Grid Connections

STATCOM for Wind

Static Var Compensators

Energy Storage

Smart Control rooms Digital SubstationsSmart Power

electronics

Smart Transmission Grids


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Generic Digital SS Architecture

Proxy

Multiple Ethernet

IEC61850.8-1

Station Bus

C37.118 Phasor Data

Grid Control

Rooms

AMU

Primary Eqpt with

embedded sensors

for Condition Monitoring

Prot. Px40

DRUs

Switches

WAN

CMU

SCS HMI

Multiple Ethernet

IEC61850.9-2 &

IEC61850.8-1

Process Bus

Digital SS ComponentsIntegrated Substation Automation System with

1. Substation Control System (SCS)

2. Condition Monitoring System (CMS)3. Smart Grid Applications (SG APPS Cyber,

Intrusion,

Wide Area Management)

4. Substation Phasor Data Concentrator

Several IEDs

1. Protection / Measurement with 9-2 interface

2. Bay Controller Unit (BCU)

3. Condition Monitoring Unit (CMU)

4. Switches & Telecom

5. Proxy Server

6. Merging Units7. Wide Area Control Unit

8. Power Quality /Disturbance Record Unit

(DRU)

9. Energy Meters

DMU

SG APPSCMS PDC

WACU

BCU

Other

substations

sPDC

SG APPS

APPS 2012 Stafford UK


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Scope



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Process Bus Elements Ethernet Network, 100 Mb/s

IEC 61850-9-2 LE for Sampled Values SV

Current measurement (CT)

Voltage measurement (VT)

IEC 61850-8-1 GOOSE Service Status position of Circuit Breaker / Switches (CB)

Trip signals from protections to CBs (Trip)

Commands from Control Systems (Open/Close)

Others (monitoring status reports, health, settings)

Time synchronisation

Microsec accuracy required


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61850-9-261850-9-2

61850-8-1

61850-8-1

Bay Level

Protection Control

Station LevelFunction A Function B

HV Equipment

Bay Level

Protection Control

HV Equipment

33

11

33

1166 66

99

44 55 44 55

88

77 Technical ServicesLogical View Of SA


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IEC 61850 -9-2 Overview

Sampled Value Transmission

Unidirectional link (MU to IED)

Physical layer : Optic fibre (copper optional)

Data Link layer : Ethernet 100 Mbit/s

Application Layer : IEC 61850-9-2 Light Edition guideline to aid

implementation and interoperability

Sampling rate : 80 or 256 samples per cycle

Neutral current and/or voltage may be measured, or derived

Sampled values are multicast on the LAN

Defines Logical Device MU

Synchronising of sampling


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4V; 4I

4V; 4I

IEC 61850-9-2LE Sampled Values

Each SV message has 4 voltages, 4 currents

Primary values, quality info

Current : 1mA to 2.14 MA, Voltage : 10mV to 21.4 MV

MU-L1

MU-L2

Protection

Bay 1Protection

Bay 2

(I1a, I1b, I1c, I1n, V1a, V1b, V1c,

V1n)

(I2a, I2b, I2c, I2n, V2a, V2b, V2c,

V2n)


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SV frames are multicast

MAC Address range: 01-0C-CD-04-00-00 to 01-0C-CD-04-1F-FF

input on Merging Units Note the frame overhead : 24 bytes of raw data (per 3-phase

voltage and current) in about 125 byte Ethernet frame

Iax1000

32bitInt

IaQuality

32bits

Ibx1000

32bitInt

IbQuality

32bits

Icx1000

32bitInt

IcQuality

32bits

Inx1000

32bitInt

InQuality

32bits

Vax1000

32

bit

Int

VaQuality

32

bits

Vbx1000

32

bit

Int

VbQuality

32

bits

Vcx1000

32

bit

Int

VcQuality

32

bits

Vnx1000

32

bit

Int

VnQuality

32

bits

-9-2LE Sampled Value Frame


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Merging Unit Typical Naming

AMU : Analogue Merging Unit Interface with conventional instrument transformers

DMU : Digital Merging Unit

Interface with CB / isolators / earth switches

CMU : Condition Monitoring Merging Unit

DMU with condition monitoring features

NMU : Numerical Merging Unit

Interface with digital instrument transformers


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CB

Status &

Trips


Conventional Bay -typical Main 1, Main 2, BCU

Individual CT cores per IED

Independent tripping paths forMain 1 and Main 2 typically



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DMU#1

-8-1PRP

AMU#1

-9-2LE

DMU#2

-8-1PRP

AMU#2

-9-2LE

AMU#3

-9-2LE

Main1

P546

-9-2LE

-8-1PRP

Main2

P446

-9-2LE

-8-1PRP

BCU

C264

-9-2LE

-8-1PRP

Process Bus

(conceptual)

Digital Bay - Typical Main 1, Main 2, BCU

AMU, DMU

Ethernet links andswitches

Time synch eqpt



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Sampling Synchronisation Why ?

Protection functions/algorithms require all input quantities to be

supplied in real time

Relay inputs may be from multiple MUs

o Substation layout

o Customer specifications

Eg: Distance Protection (Voltage & Current)

Both voltage & current supplied by one MU; synchronisation provided by

the MUVoltage from MU1 and Current from MU2; synchronisation by common

time reference input to MU


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AMU #2

-9-2LE

V 0

I 36

V 18

I 81

1 ms delay

2.5 ms delay


SV frames from different MU may have uneven delays

Relay measurements will be incorrect unless the SV frames are timealigned

SV frames from different MU may have uneven delays

Relay measurements will be incorrect unless the SV frames are timealigned


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Sampling Synchronisation - Techniques

1 PPS input on Merging Units

Merging Units with capability for IEEE 1588 synchronisation

Sampled Value frames carry synchronisation info

Time tags (count) relative to the start of the sec

Identifier for sync source Global, Local or No Sync

Indicates if the SV

frame is synchronised

Sample Count0 3999 at 50 Hz

0 4799 at 60 Hz

Counter resets every sec when a

time sync signal is received


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Sampled Values Alignment in Relays


Time alignment of SV frames is necessary, and ensures correct

operation of protection functions dependent on multiple MUs The number of MUs may change depending on site

requirements and customer preferences

Delays arise from

Merging Units, due to their processing

Network, depending on its configuration and switches

Delays have a direct impact on the operating time of the scheme

Time tags (count) relative to the start of the sec

Identifier for sync source Global, Local or No Sync



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Sampled Values Alignment in Relays


Case 1: Relay with

1 MU

Case 2: Relay with

2 MU

Case 3: Relay with

2 MU

MU Delay: Relay setting,

indicates worst case relative

delay expected in receiving

SV from all MUs linked to

the relay

In this case, no delaybetween SV frames from

MU#1 and MU#2

In this case, there is a 1msdelay between SV frames

from MU#1 and MU#2



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Sampling Synchronisation Accuracy

Time source accuracy +/- 1s SamplingacrossmultipleMUs synchronisedtowithin+/ 4s

MUshouldbecapableofcompensatingnetworkdelays>2s

MiCOM P594


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Sampling Synchronisation 1 PPS

1PPS signal, transmitted by fibre as medium

Rise and fall time < 20ns

Clock source : Typically based on GPS

Global 1PPS: GPS is alive, pulse width between 5s and 500 ms

Local 1PPS : Pulse width between 0.9s and 1.1s

No Sync : Merging Unit hold-over mode

1PPS

-9-2LE SAV

P594 Merging Unit


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IEC 61850-9-2 Overview

Sampling Synchronisation IEEE 1588

It is a high precision time synchronization (


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How does IEEE 1588 compare with NTP (SNTP) ?

Master/slave arrangement, against peer-peer in NTP

Target of microsec accuracy vs millisec in NTP

NTP is intended for internet, IEEE 1588 for LAN with few subnets

Smaller network message & computation requirement

Both include latency correction NTP has to be configured, whereas IEEE1588 is self-organising

Master Slave / Master Slave / Master


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t1 t4

t2 t3

Sync message from Master

Follow Up message from Master with value of t1

Delay Request message from Slave

Delay Response from Master with value of t4

Master

Slave

t1, t2, t3, t4

known to Slave

IEEE 1588 - Time correction on the network


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MS = t2 t1 = Clock offset + MS delay

SM = t4 t3 = Clock offset + SM delay

Clock offset = {( MS SM) (MS delay SM delay )}/2

MS delay + SM delay = { MS + SM }

ASSUME: MS delay = SM delay = Path delay

Then:

Clock offset = { MS SM}/2

Path delay= { MS + SM}/2

M : Master ClockS : Slave Clock

IEEE 1588 - Time correction on the network


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Scope


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IEDs for Process Bus ApplicationsRelay - Example

MiCOM P444 Distance Relay with SV Interface

Have the 9-2 board instead of the Analogue module The 9-2 module resamples the SV received

Analogue module output on the internal bus at relay sampling rate No change in protection algorithms

Selection of SV inputs

/ Logical Nodes


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IEDs for Process Bus ApplicationsRelay - Example

Px4x Process Bus Interface

Interface for -9-2LESampled Values

Interface for -8-1 GOOSE


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IEDs for Process Bus ApplicationsRelays

Point to point connections

Feasible when all the SV required by a relay areavailable from a single MU

Simple network, minimum delay, minimalengineering effort

Interfacing SV to Relays

MiCOM P446

IEC 61850

MergingUnit 1

IA1, IB1, IC1

VA, VB, VC


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Interfacing SV to Relays Transformer

Protection

P645

HV+LV+TV

HV Current - 1

HV Current 2

TV Current - 1

TV Current - 2

LV Current

Point to point

connection

not possible

Point to point

connection

not possible



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Networked connections

Required if the SV required by a relay are from multiple MU,eg: transformer IED, busbar IED

Ethernet switch(es) involved, possibility of additional delays

and sample jitter; substation-hardened switches required,similar to Station Bus applications.


-9-2LE


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Networked connections - redundancy

Network redundancy for SV may be achieved by externaldevices such as a RedBox, or it may be integral to the relay

Note that network redundancy only accounts for

communication link failures


LAN A

LAN B


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Settings for relay / MU configuration Logical Nodes

Number of MU could vary with application



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IEDs for Process Bus ApplicationsMerging Units

Merging units perform all the digital data processing necessary to produce aprecise, time-aligned output data stream of sampled values according to the

IEC 61850-9-2 standard

Includes tasks such as sampling, analogue to digital conversion, scaling,precise real-time referencing to the start of the last second and messageformatting

Design varies with the applied technology of the instrument transformers (eg:optical, Rogowski, voltage dividers, or conventional wound instrumenttransformers), the switchgear type and mounting space available

Alstom Grid portfolio will cover such solutions, for application in new

substations with digital NCITs, as well as refurbishments of olderconventional substations, or partial replacement by new sensors.


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FUNCTIONALITY TRANSFERRED

TO AN ANALOGUE MERGING UNIT

FUNCTIONALITY TRANSFERRED

TO A DIGITAL MERGING UNIT

IEDs for Process Bus ApplicationsMerging Units - Functionality


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IEDs for Process Bus ApplicationsMerging Units - Mounting


Located in the switchyard in the case of AIS Close to primary eqpt, inside LCC, for instance

Fibre optic cabling for protection signals


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IEDs for Process Bus ApplicationsEthernet Switches

What are the requirements for switches on Process Bus ?

Industrial, substation-hardened

Switches should be managed, to optimise LAN performance

Check the number of Fibre / Copper ports available and compare

with the application requirements

Switches should be VLAN-aware

Switches that are transparent clocks for IEEE 1588, where requiredfor time synchronisation

!! Protection scheme is dependent on switches !!

Typically, switches would be located with protection / BCU

Other IEDs may, optionally, integral a switch board


IED f P B A li i


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IEC 61850-3 : Switches , like relays, should comply with the

type withstands tests designed to simulate substation EMIphenomena such as:

Lightning impulses

Switching of inductive loads

Electrostatic discharges

Radio frequency interference due to portable radio handsets

Earth potential rise resulting from system fault conditions


IED f P B A li i


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IEEE 1618 : Standard for Environmental and Testing

Requirements for Communications Networking Devices in

Electric Power Substations

Defines optional Class 2 - requires that, during the

application of the type tests, the switch must exhibit:

No communications errors

No communications delays

No communication interruptions


IED f P B A li ti


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IEDs for Process Bus ApplicationsEthernet Switches - Example

Cascading H356 for additional ports

4 x LC Multimode

2 x RJ45



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Scope


hi l


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Process Bus Architecture ExamplesSingle AMU-DMU

Process Bus

IEC61850-8.1 and 9-2

Ethernet 100 Mbps

BCU MP2 MP1

Note: Conceptual architecture only,

the functionality of MP1, MP2 etc. is unspecified

-9-2-8-1

Control Room

Switchyard / GIS Room

Separate networks for-8-1 and -9-2

One CT core, SVdistributed by singleAMU

Status / trips viasingle DMU

Single AMU / DMU,thus failure affects fullprotection & control ofthe bay

Switch failure affects

full protection andcontrol of the bay

Substation Grade

Ethernet Switch

AMUDMU

ESW ESW

ESW


P B A hi E l


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Process Bus Architecture ExamplesDual AMU-DMU

Process Bus

IEC61850-8.1 and 9-2

Ethernet 100 Mbps

BCU MP2 MP1

Note: Conceptual architecture only,

the functionality of MP1, MP2 etc. is unspecified

-9-2-8-1

Control Room

Switchyard / GIS Room

Main 1 and Main 2protections haveindependent AMU and

DMU, separatenetworks

SV and GOOSE forBCU and MP2 sharecommon switch

Independent CT coresfor Main 1 and Main 2via AMU1 and AMU2

Two independent tripoutputs available DMU1 and DMU2

Substation Grade

Ethernet Switch

AMUDMU

ESW

ESW

AMU

DMU

-9-2 -8-1



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Time synchronisation for sampled values

Distribution of busbar voltage for check sync

Merging Unit with redundant ports

IEDs with redundant ports for Process Bus

Merging Unit common for analogues and digitals

Process Bus Architectures

Whats missing in the previous architectures ?

> Architecture must be optimised for the application

iec 61850 process bus

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