to goose or not to goose that is the question.pdf

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To GOOSE or Not to GOOSE? – that is the question  Alexander Apostolov PAC World 1 Introduction IEC 61850 is being widely accepted around the world due to significant benefits that it provides compared with conventional hard wired solutions. However, there are still many specialists in the industry that are hesitating to make a decision and start using GOOSE messages for all the different protection and protection related functions. This is probably due mainly to the lack of understanding of the differences between hardwired and GOOSE based solutions. Taking advantage of the benefits is possible only when there is good understanding of the fundamentals and the applications. That is why the paper first introduces the concepts of the IEC 61850 GOOSE (Generic Object Oriented Substation Event). It describes:  Publisher and Subscriber functionality  Multicasting  Event reporting versus commands  Priority tagging  VLAN  Repetition mechanism  Data sets  Simulation bit The benefits of the IEC GOOSE are then described. Availability, security and performance issues are discussed. Interoperability and its impact on protection applications are analyzed. 2 GOOSE Basics The IEC 61850 international standard for power system communications is developed to meet the different requirements of protection, control, monitoring, recording, data acquisition, etc. functions. It allows the implementation of a new set of applications that will result in significant improvement of the functionality and at the same time reduction in the cost of substation automation systems. 2.1 Communication Types in Substation Automation Systems In order to understand the need for the development of GOOSE messages we need to consider the communications withi n substations. One of the most commonly used is Client – Server. The client in this domain can be defined as a device or function that sends a message to a server device or function, requesting from the server to perform a specific task (service). The client application usually manages the user-interface portion of the application, validates data entered by the user or sends requests to the servers. The client-based process is the front- end of the application that the user sees and interacts with in the substation automation system.  A server device or function fulfills the client request by performing the requested task. Most IEDs in the substation operate as servers while interfacing with bay or substation level devices or applications. Bay level devices can function both as clients (when interfacing with the equipment level IEDs) or servers (when interacting with the substation level functions.  A typical Client/Server operation is a complete transaction consisting of a request followed by information delivery of the requested information. It is important to note that one server can 583 978-1-4799-8722-1/15/$31.00 ©2015 IEEE ProRelay 2015

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To GOOSE or Not to GOOSE? – that is the question 

 Alexander Apostolov

PAC World

1 Introduction

IEC 61850 is being widely accepted around the world due to significant benefits that it providescompared with conventional hard wired solutions. However, there are still many specialists in theindustry that are hesitating to make a decision and start using GOOSE messages for all thedifferent protection and protection related functions. This is probably due mainly to the lack ofunderstanding of the differences between hardwired and GOOSE based solutions. Takingadvantage of the benefits is possible only when there is good understanding of the fundamentalsand the applications.

That is why the paper first introduces the concepts of the IEC 61850 GOOSE (Generic ObjectOriented Substation Event). It describes:

•  Publisher and Subscriber functionality•  Multicasting

•  Event reporting versus commands

•  Priority tagging

•  VLAN

•  Repetition mechanism

•  Data sets

•  Simulation bit

The benefits of the IEC GOOSE are then described. Availability, security and performance issuesare discussed. Interoperability and its impact on protection applications are analyzed.

2 GOOSE Basics

The IEC 61850 international standard for power system communications is developed to meet thedifferent requirements of protection, control, monitoring, recording, data acquisition, etc. functions.It allows the implementation of a new set of applications that will result in significant improvementof the functionality and at the same time reduction in the cost of substation automation systems.

2.1 Communication Types in Substation Automation Systems

In order to understand the need for the development of GOOSE messages we need to consider thecommunications within substations. One of the most commonly used is Client – Server. The clientin this domain can be defined as a device or function that sends a message to a server device orfunction, requesting from the server to perform a specific task (service).

The client application usually manages the user-interface portion of the application, validates dataentered by the user or sends requests to the servers. The client-based process is the front- end of

the application that the user sees and interacts with in the substation automation system.

 A server device or function fulfills the client request by performing the requested task. Most IEDs inthe substation operate as servers while interfacing with bay or substation level devices orapplications.

Bay level devices can function both as clients (when interfacing with the equipment level IEDs) orservers (when interacting with the substation level functions.

 A typical Client/Server operation is a complete transaction consisting of a request followed byinformation delivery of the requested information. It is important to note that one server can

583978-1-4799-8722-1/15/$31.00 ©2015 IEEE ProRelay 2015

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respond to the requests of multiple clients and vice versa. Usually data flows primarily from theserver to the clients.

Master/Slave communications can be described as a management scheme called polling in whichone IED (the Master) requests specified information from one of a group of IEDs (Slaves) to bedelivered. Only Masters, not Slaves, may issue unsolicited data or commands. This type ofcommunications is not very efficient due to the fact that it results in exchange of information even

when there is no change of state or values. It is used where data flows primarily between theSlaves and the Master.

The Client/Server communications can also be described as connection-oriented, which meansthat the devices at the end points establish an end-to-end connection before any data is sent.Connection-oriented communications are considered a more reliable network service, becausethey guarantee that data will arrive in the proper sequence. The Transmission Control Protocol(TCP) is a connection-oriented protocol.

The problem with Client/Server communications is that due to their principles they cannot meet therequirements for performance, especially for protection applications. This resulted in the idea fordevelopment of different types of communications based on a Connectionless method. In this casedata is sent from one device to another without prior arrangement. Connectionless protocols areusually described as stateless, because the end points have no protocol-defined way to rememberwhere they are in a "conversation" of message exchanges. Since an IED transmits data to another

device without first ensuring that the recipient is available and ready to receive the data, there is noguarantee that the data will be received. The device sending a message simply sends it addressedto the intended recipient. Because of that IEC 61850 has introduced specific mechanisms toensure the delivery of the data to the recipients.

Peer-to-peer is the characteristic communications type for the IEC 61850 based systems. It is oneof the distinguishing features of the standard that makes it attractive to protection and controlspecialists. It describes the ability of arbitrary pairs of IEDs connected to the substation network tomanage the exchange of information as necessary with all devices having equal rights, in contrastto the master/slave communication.

Fig. 1 Multicast communications

Peer-to-peer communications in IEC 61850 based systems use multicast for data delivery. It is amethod that allows the sending IED to deliver the information simultaneously to a group of

destination IEDs using the most efficient strategy - to send the messages over the network onlyonce. By comparison with multicast, conventional point-to-single-point delivery is called unicast.

Peer-to-peer communications are used to perform protection, control, monitoring and recordingfunctions. Any function can be divided into sub-functions and functional elements. The functionalelements are the smallest parts of a function that can exchange data. These functional elements inIEC 61850 are called Logical Nodes [1, 2]. When a function is executed based on the exchange ofcommunications messages between two or more devices, it is called “distributed function”.

The exchange of data is not only between functional elements, but also between different levels ofthe substation functional hierarchy. It should be kept in mind that functions at different levels of the

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functional hierarchy can be located in the same physical device, and at the same time differentphysical devices can be exchanging data at the same functional level.

Figure 2 shows Logical Connections (LC) - the communication links between functional elements -in this case logical nodes of the P and R groups. IEC 61850 also defines interfaces that may usededicated or shared physical connections - the communication links between physical devices.

Fig. 2 Distributed Function definition in IEC 61850

The allocation of functions between different physical devices defines the requirements for thephysical interfaces, and in some cases may be implemented into more than one physical LANs.The functions in the substation can be distributed between IEDs on the same, or on different levelsof the substation functional hierarchy. IEC 61850 [1] defines three such levels:

•  Station

•  Bay/Unit

•  ProcessThese levels and the logical interfaces are shown by the logical interpretation of Figure 3. IEC

61850 focuses on a subset of the interfaces shown in Figure 3 with Interface 8 (shown in red) beingused for high-speed peer-to-peer communications.

Fig. 3 Logical interfaces in Substation Automation Systems

 Bay

computer 

Distributed

function

 IF 8LC1

P..

R...LC2

 Protection

 IED

 IF 8

 Protection

 IED

P...

R...

P...

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The logical interfaces IF8 is defined [1] as direct data exchange between the bays especially forfast functions like interlocking.

In order to implement high-speed protection and control functions over the substation local areanetwork, we need to make sure that the system will meet some specific performance requirements.Different distributed functions impose different performance requirements that have to beconsidered in the design process of substation protection, control, monitoring and recording

systems.There are two independent groups of performance classes:

•  for control and protection

•  for metering or power quality applicationsSince the performance classes are defined according to the required functionality, they areindependent from the size of the substation. The requirements for control and protection are higher,because of the effect of the fault clearing time on the stability of the system or on sensitive loads.IEC 61850 defines three Performance Classes for such applications:

P1 - applies typically to the distribution level of the substation or in cases where lower performancerequirements can be accepted.

P2 - applies typically to the transmission level or if not otherwise specified by the user.

P3  - applies typically to transmission level applications with high requirements, such as bus

protection.IEC 61850 transfer time definition [1] is based on Figure 4 below:

Fig. 4 Transfer time definition

Where:

ta - time from the moment the sending IED (PD[n] in Figure 4) puts the data content on top of itstransmission stack until the message is sent on the network

tb - the time over the network

tc  - the time from the moment the receiving IED (PD[m] in Figure 4) gets the message from the

network until the moment it extracts the data from its transmission stackThe overall performance requirements also depend on the message type. Type 1 is defined in thestandard as Fast Messages. Since Trip (Type 1A) is the most important fast message in thesubstation, it has more demanding requirements compared to all other fast messages. The sameperformance may be requested for interlocking, intertrips and logic discrimination betweenprotection functions.

For Performance Class P1, the total transmission time shall be in the order of half a cycle.Therefore, 10 ms is defined. For Performance Class P2/3, the total transmission time shall be

Communi-cationprocessor 

f i f k

Physical device PD[n] Physical device PD[m]

Transfer time t = ta + tb + tc

ta tb tc

Communi-cationprocessor 

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below the order of a quarter of a cycle. Therefore, 3 ms is defined for the high-speed peer-to-peercommunications.

The communications of data between different multifunctional IEDs working together in distributedfunctions are achieved over the substation LAN. In order to understand some of the specificfeatures included in the IEC 61850 design of high-speed peer-to-peer communications, we need tolook first into the type of Ethernet frames being used.

The performance of GOOSE based schemes is consistently better than the performance ofconventional hard-wired schemes. This is due to the fact that if we apply the same definitions forthe transfer time between two IEDs connect with wires, the communications interface of thesending IED is a relay output with typical time about 3 ms, while the communications interface ofthe receiving IED is the opto input. Depending on the design of the IED this interface can introducea non-deterministic behavior which may result in delays up to half cycle.

2.2 Ethernet Frames and GOOSE

Ethernet is used for substation communications based on the IEC 61850 standard. The Ethernet inthis case is not the hub based collision detection protocol from 10 years ago. It is the advancedhigh-speed protocol of today. Perhaps the most important advancement in Ethernet networks is theuse of switched Ethernet. Switched networks replace the shared medium of legacy Ethernet with a

dedicated segment for each IED. These segments connect to a switch, which acts much like anEthernet bridge, but can connect many of these single segments. Some switches today cansupport hundreds of dedicated segments. Since the only devices on the segments are the switchand the end device, the switch picks up every transmission before it reaches another node. Theswitch then forwards the frame over the appropriate segment, and since any segment contains onlya single node, the frame reaches only the intended recipient, thus allowing many conversations tooccur simultaneously on a switched network.

 Another technological advancement is full-duplex Ethernet. Full-duplex is a data communicationsterm that refers to the ability to send and receive data at the same time. Legacy Ethernet is half-duplex, meaning information can move in only one direction at a time. In a totally switched network,nodes only communicate with the switch and never directly with each other. Switched networksalso employ either twisted pair or fiber optic cabling, both of which use separate conductors forsending and receiving data. In the substation environment fiber is the preferred option.

In switched Ethernet the devices connected to the network can forgo the collision detection processand transmit at will, since they are the only potential devices that can access the medium. The endstations in this case can transmit to the switch at the same time that the switch transmits to them,achieving a collision-free environment. That allows the development of new functionality insubstation automation systems practically impossible in the hub based LAN at the early stages ofthe development of UCA 2.0 GOMSFE.

The performance of protection and other distributed functions is further improved through theavailability of priority tagging defined, while improvements in security are the result of using aVirtual LAN (VLAN). VLAN is a group of devices on one or more LANs that are configured in such away that they can communicate as if they were attached to the same wire, when in fact they arelocated on a number of different LAN segments. The IEEE 802.1Q specification establishes astandard method for tagging Ethernet frames with VLAN membership information. The key for theIEEE 802.1Q to perform the above functions is in its tags. 802.1Q-compliant switch ports can be

configured to transmit tagged or untagged frames. A tag field containing VLAN (and/or 802.1ppriority) information can be inserted into an Ethernet frame.

The format of the IEEE 802.1Q header is:

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TPID is the Tag Protocol Identifier - a 16-bit field set to a value of 0x8100 that identifies the frameas an IEEE 802.1Q-tagged frame.

PCP is the Priority Code Point- a 3-bit field which refers to the IEEE 802.1p priority. It indicates theframe priority level from 0 (lowest) to 7 (highest) and can be used to prioritize different classes oftraffic like GOOSE or sampled values messages.

CFI  is the Canonical Format Indicator - a 1-bit field. If the value is 0, the MAC address is in

canonical format – the setting for Ethernet switches.VID is the VLAN Identifier - a 12-bit field specifying the VLAN to which the frame belongs. A valueof 0 means that the frame doesn't belong to any VLAN; in this case the 802.1Q tag specifies only apriority and is referred to as a priority tag. A value of hex FFF is reserved for implementation use.

 All other values may be used as VLAN identifiers, allowing up to 4094 VLANs.

If a port has an 802.1Q-compliant device attached (such as another switch), these tagged framescan carry VLAN membership information between switches, thus letting a VLAN span multipleswitches.

Table 1  Ethernet Type II frame

Where:

Destination address (6 bytes) identifies which station(s) should receive the frame

Source addresses (6 bytes) identifies the sending station

Ethertype is a 2 byte code indicating protocol type in an Ethernet packet. The Ethertypes related toIEC 61850 GSE are as follows:

IEC 61850 8-1 GOOSE: 88-B8

IEC 61850 8-1 GSE Management: 88-B9

The tagged Ethernet frame shown in Table 1 can help us understand how different communicationmodes work in the Ethernet network environment.

2.3 GOOSE Model

High-speed peer-to-peer communications in IEC 61850 based protection and control systems usea specific method designed to meet a variety of requirements. It is very important that the conceptof the Generic Substation Event (GSE) model is not based on commands, but on the sendingindication by a function that a specific substation event has occurred. It is designed to supportreliable high-speed communications between different devices or applications and allows thereplacement of hard-wired signals between devices with communication messages exchange whileimproving the functionality of the protection, automation and control system.

The model includes several features that can be used to improve the reliability and availability ofthe system. At the same time the proper use of these features in vendors’ implementation will allow

the reduction in maintenance and increase in the flexibility of the system. To understand thereasons for these benefits, we need to look into some of the details of the Generic SubstationEvent model.

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Fig. 5 Publisher/Subscriber mechanism

The GSE method can be considered as a mechanism for reporting by a logical device. Theachievement of speed performance, availability and reliability depends on the implementation inany specific device.

The generic substation event model is used to exchange the values of a collection of Data Attributes defined as a Data Set. Two types of messages are defined in Edition1 of IEC 61850:

•  GSSE – Generic Substation State Event that includes state information only (represented by bitpairs).

•  GOOSE - Generic Object Oriented Substation Event that supports the exchange of a wide range

data types organized in a data set

Fig. 6 Publisher functionality

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The GSSE was included in IEC 61850 to support backward compatibility with legacy UCA 2systems as defined in GOMSFE (Generic Object Model for Substation and Feeder Equipment). Itis not included in Edition 2 of the standard.

The GSE information exchange is based on a publisher/subscriber mechanism.

The publisher writes the values in a transmission buffer at the sending side and multicasts themover the substation local area network to the different subscribers – clients or servers.

The data in the published GOOSE messages is a collection of values of data attributes defined asmembers of a data set. The receiver reads the values from a local buffer at the receiving side. AGSE control class in the publisher is used to control the process. If the value of at least one of theDataAttributes has changed, the transmission buffer of the Publisher is updated with the localservice “publish” and the values are transmitted with a GOOSE message.

The publisher/subscriber mechanism allows the source IED to reach multiple receiving IEDs thussignificantly improving the efficiency of the communications interface.

Specific communication services in the subscribers update the content of their reception buffersand new values received are indicated to the related applications.

Since the GOOSE messages replace hard-wired signals used for protection and controlapplications IEC 61850 introduces mechanisms that ensure the delivery of the requiredinformation.

Once a new value of a date attributed has resulted in the multicasting of a new GOOSE message,the repetition mechanism ensures that the message is sent with a changing time interval betweenthe repeated messages until a new change event occurs.

Fig. 7 GOOSE repetition mechanism

 As shown in Figure 7, at the beginning after a change the interval is very short – a fewmilliseconds, which later increases until it reaches a value of a few seconds. This method achievesseveral important tasks:

•  Ensures that a loss of a single message is not going to affect the functionality of the system

•  Allows any new device to inform all subscribing devices about its state

•  Allows any new device to learn the state of all publishing devices it subscribes toThe GOOSE messages contain information that allows the receiving devices to know not only thata status has changed, but also the time of the last status change. This allows a receiving device to

set local timers relating to a given event.

 At the same time the repetition mechanism can be used as a heartbeat that allows the continuousmonitoring of the communications interface – something that is not possible in conventional hardwired systems.

The state number and the sequence number can be used to detect intrusion, thus allowingsignificant improvement in the cyber security of the system without the need for encryption or othercyber security methods.

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The GOOSE Control Block class (Figure 8) includes attributes that define the behavior of the peer-to-peer communications and is related to a logical device, and more specifically to its LLN0.

GoCBName (GOOSE control name) identifies a GoCB within the scope of a GoCBRef (GOOSEcontrol reference) - a unique path-name of a GoCB within LLN0:

LDName/LLN0.GoCBName

GoEna (GOOSE enable) indicates that the GoCB is Enabled (if set to TRUE) to send GOOSE

messages. If set to FALSE it shall stop sending GOOSE messages. AppID is an application identification represented by a visible string that represents a logical devicein which the GoCB is located.

Fig. 8 GOOSE Control Block class

DatSet is the reference of the data set whose values of members shall be transmitted.

ConfRev is the configuration revision indicating the number of times that the configuration of thedata set referenced by DatSet has been changed. The counter is incremented every time when the

configuration changes.

NdsCom (needs commissioning) is TRUE if the attribute DatSet has a value of NULL and is used toindicate that the GoCB requires configuration.

 As already mentioned, the content of the GOOSE message (shown in Figure 9) allows thereceiving devices to perform processing of the data in order to execute required actions. Some ofthe attributes in the GOOSE message that help perform the functions described earlier are:

T – the time stamp representing the time at which the attribute StNum was incremented.

StNum indicates the current state number - a counter that increments every time a GOOSEmessage (including a changed value) has been sent for the first time. The initial value is 1.

SqNum is the sequence number – the value of a counter that increments each time a GOOSEmessage with the same values has been sent. The initial value is 1.

Simulation is a parameter that indicates that the GOOSE message is used for test purposes (if thevalue is TRUE) and that the values of the message have been issued by a simulation unit and shallnot be used for operational purposes. The GOOSE subscriber will report the value of the simulatedmessage to its application instead of the ―realǁ message depending on the setting of the receivingIED.

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Fig. 9 GOOSE message

The basic concept described above applies also to the GSSE model is similar to the GOOSE  model. However, there are a couple of major differences:

•  GOOSE provides flexibility in the definition of a data set with different data types, while GSSE provides only a simple list of status information.

•  While the mapping of GOOSE to IEC 61850 8-1 supports VLAN and priority tagging, these arenot available in GSSE messages

3 GOOSE Benefits

The GOOSE model described above allows the development of protection and control systems thatoffer some significant advantages compared with conventional hard-wired systems:

3.1 Reduced Installation Costs

One of the easiest to calculate benefits of GOOSE based protection and control system benefits isthe reduced installation costs. They include several components:

•  Reduced costs due to the replacement of hundreds or even thousands (in large substations)control cables with a limited number of fiber optic cables

•  Reduced costs due to the replacement of the wiring of hundreds of copper wires to thepanels’ terminal blocks and then from the terminal blocks to the relay terminals with theplugging in of a single pair of fiber cables connecters to the communication ports of theEthernet switch and the multifunctional protection IED

•  Reduced costs due to the requirements for testing of all hard wired interfaces versus thetesting of the GOOSE messages based on advanced software tools

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Fig. 10 Hard-wired panel

3.2 Improved Flexibility

One of the big challenges in updating protection and control systems due to changing requirements,better solutions or extensions of the substation is the need to physically remove and add controlcables between the individual IES and the panels. This is a time consuming process that also is mademuch worse in the case of remote substations that may be difficult to reach, especially under difficultweather conditions. Improved flexibility of the system is achieved when using GOOSE messages due

to the use of virtual signals described in a standard substation configuration language format. In manycases adapting the protection and control scheme to the new requirements can be achieved withoutthe need for physical presence in the substation.

3.3 Reduced Maintenance

Time based (or Scheduled) maintenance is also a very expensive activity that is required to performin order to ensure that all hard wired interfaces between the individual components of the protectionand control system are functioning properly. This is due to the fact that the hard wired connectionscannot be monitored. That is why they need to be tested based on the accepted utility practice.Reduced maintenance due to the fact that the state of the different components of the system and theinterfaces between them can be continuously monitored. Depending on the communicationsarchitecture the condition monitoring system may determine which the failed component that may

require maintenance is.If the communication interface uses a single copy of a message and a specific GOOSE message isnot received within the expected time interval defined by the repetition mechanism shown in Figure 7,this will indicate that there is a problem with the publishing IED or the fiber optic cable between theIED and the Ethernet switch.

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Fig. 11 PRP based communications architecture

However, if the system is using a PRP (Parallel Redundancy Protocol) based architecture that usestwo copies of each message, it is possible to pinpoint if there is a failure of the publishing IED (whenboth copies of the message are not received within the expected time interval) or a failure of a fiberoptic interface (if only one copy is not received).

This continuous monitoring is very important because it allows the user to detect the failure of aprotection and control system component immediately after it occurs, while if the system is hard-wiredit will be detected only if the system fails to operate when necessary or during the scheduledmaintenance testing.

3.4 Improved interoperability and reliability

One of the challenges for conventional communications based protection systems for transmissionlines is that they use manufacturer proprietary communications protocols. Even that the schemes canbe redundant in order to ensure fault clearing without time delay in an N-1 case, it is still possible forthe scheme to fail in many N-2 cases - for example the failure of one IED and the communicationschannel using by the second set of relays.The use of GOOSE messages by all protection IED suppliers allows interoperability between them

due to the use of standard high-speed communications between devices of different manufacturersover a standard communications interface. This improves the reliability of the system based on thesubscription of both IEDs on each side of the protected line to the messages from both relays at theother end of the line.

switched local

area network

(tree) LAN_B

RB

switched local

area network

(ring) LAN_A

DANP

DANP DANP DANP

SAN

 A2 SAN

B1

SAN

B2

SAN

 A1

SAN

R1

SAN

R2

DANP

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Fig. 12 Communications based transmission line protection scheme

3.5 Remote Testing

Maintenance testing in cases such as relay mal-operation require its testing before putting it inoperation. In the typical cases this requires sending a testing crew to the substation to perform thetesting – a time consuming and expensive process.The use of protection systems in a digital substation environment allows the testing to be performedremotely, however the use of both sampled values and GOOSE messages is required for the end-to-end testing. For the testing of part of a scheme that is affected by the modifications, it is possible todo the remote testing using the testing features from IEC 61850 Edition 2. This supports the ability to

test a subset of functions and their elements while keeping the rest of the system in operation.4 Conclusions

IEC 61850 - the international standard for substation communications - enables the development ofa range of conventional and new types of applications based on high-speed Peer-to-Peercommunications using GOOSE messages.

The communications in the substation automation system can be between devices at the samelevel of the functional hierarchy or between the substation, bay and process levels of the system.

The different types of communications have to meet specific performance requirements defined indetails by the standard.

Switched Ethernet eliminates many of the concerns regarding non-deterministic operation withinthe substation automation system. VLAN and Priority tagging need to be supported by thehardware and the applications in order to ensure high-speed operation for time critical functions

such as protection and control.

The GOOSE model includes different attributes that allow the achievement of significant benefitscompared to conventional hard-wired systems.

So the answer to the question in the title of the paper is definitely “To GOOSE!”

5 References

[1]IEC 61850-1 Communication Networks and Systems in Substations, Part 1: Introduction and Overview

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[2]IEC 61850-5 Communication Networks and Systems in Substations, Part 5: CommunicationRequirements for Functions and Device Models[3]IEC 61850-7-2: Communication Networks and Systems in Substations, Part 7-2: Basic communicationstructure for substations and feeder equipment – Abstract communication service interface (ACSI)

6 Biography 

Dr. Alexander Apostolov  received MS degree in Electrical Engineering,MS in Applied Mathematics and Ph.D. from the Technical University inSofia, Bulgaria. He has 40 years’ experience in power systems protection,automation, control and communications.

He is presently Principal Engineer for OMICRON electronics in Los Angeles, CA. He is IEEE Fellow and Member of the Power SystemsRelaying Committee and Substations C0 Subcommittee. He is pastChairman of the Relay Communications Subcommittee, serves on manyIEEE PES Working Groups and is Chairman of Working Groups C2 “Role

of Protective Relaying in Smart Grid”.

He is member of IEC TC57 working groups 10, 17, 18 and 19 and Convener of CIGRE WG B5.53”Test Strategy for Protection, Automation and Control (PAC) functions in a full digital substationbased on IEC 61850 applications” and member of several other CIGRE B5 working groups. He holdsfour patents and has authored and presented more than 400 technical papers.

He is IEEE Distinguished Lecturer and Adjunct Professor at the Department of Electrical Engineering,Cape Peninsula University of Technology, Cape Town, South Africa.

He is Editor-in-Chief of PAC World.

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