advantage of iec 61850

Track 3: POWER AND SYSTEMS ENGINEERING

International Symposium on Electrical & Electronics Engineering 2007 - Oct 24, 25 2007 - HCM City, Vietnam

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THE ADVANTAGE OF STANDARD IEC61850

IN PROTECTION AND SUBSTATION AUTOMATION SYSTEMS

Assoc. Prof. PhD. Le Kim Hung - Danang University, PhD. Thach Le Khiem - ABB VietNam, and Ivan De Mesmaeker - ABB Switzerland

ABSTRACT

The use of numerical technology in protection and automation has provided multi-functions

equipment, allows the development of new solutions and a higher degree of integration. The paper

give the general functions, advantage and how to use IEC61850 in design, engineering application for

substation protection and control.

1. INTRODUCTION AND ADVANTAGE

OF IEC 61850

The standard IEC61850 - Communication

Networks and Systems is the first and only

global standard that considers all the

communication needs within a substation, it is

covering design aspects, defines guidelines for protection, monitoring, control and automation

This standard also raises interoperability and

free allocation of functions and devices, support all type of architectures protocol and its practical

application for substation automation systems.

IEC 61850 is not only issued, but also ready

to use in many countries. This standard is also

the request strictly by EVN (Electricity in

VietNam) for the substation automation design

in all 500kV and 220kV substation of VietNam

power system.

The advantage of IEC 61850 communication

and protocol:

- Apply the request an open protocol for

protection, monitoring, control at least inside substations.

- This is higher flexibility solution, have the

possibility to make extension without being

dependant on the manufacturer having delivered

the previous parts of the substation equipment.

- Full application and all request for

substation automation, and data interoperability

within the substations.

- Advantage for users: the system

engineering done and documented with the help

of Substation Configuration description

Language (SCL) provided in the IEC 61850-6

can be re-used later when only certain system

components have to be replaced after several

years of operation. By introducing this kind of

global language and established common naming of the function-related signal name, the

substation automation will be complemented by

a hierarchical plant designation scheme in IEC 61850. Since the standard is accepted

worldwide, no difference between the ANSI and

IEC worlds will appear.

2. IMPACT OF IEC 61850 ON

SPECIFICATIONS

The standard has an impact on all activities of field of protection and substation automation,

but the main issues are how to implement this

standard in practice which is to be done by the suppliers, and how to specify protection and

substation automation systems, which is to be

done by the users like utilities. Specifying according to the standard IEC 61850 means that

the entire functionality is split into Logical

Nodes (Fig.1) with their corresponding data, i.e.

with the established common naming of the

function-related signal names. If this is not done

in the specification already, the system

integrator has to do it. Anyway, the people

anywhere in charge of the project execution

(design, engineering, testing, FAT- Factory

Acceptance Test, commissioning, site



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Fig.1 Modelling example of one

feeder in IEC 61850

acceptance test, operation, etc.) will once have to learn this common but simple language. It is

an advantage to, the use of the Standard

Configuration description Language (SCL) has an important advantage: the integrity of data is

warranted by using one single data entry. The

users are recommended to check the signals and

evaluate which ones are really needed

(mandatory (M)/ optional (O)) which the system

designer and integrator take this information

into its design and engineering tool.

- Impacts on the general system design

Based on the specification a solution concept

has to be elaborated. The standard IEC 61850 allows the free allocation of functions. Due to

the split into functional nodes, the system

designer is free to distribute the functions, but has to respect the mentioned constraints as

imposed by the specification. To ensure

seamless interoperability, especially the

distributed functions like breaker failure

protection, busbar protection, station-wide

interlocking, and load shedding have to be designed very carefully. Regarding all the

requirements, only a system integrator with

comprehensive experience will be able to elaborate such an optimized solution exploiting

all benefits of IEC 61850.

- Impacts on the engineering

The informal information from the

specification has to be translated into the formal description using SCL. This work may

be done by the author of the specification or has

to be done latest by the system integrator. The

formal description warrants a high quality of

work, ensures integrity and consistency during

the entire implementation process, from the

general system design to the final

commissioning, facilitating the corresponding

checks in each step of the project execution.

The whole substation automation system is

formally documented in SCL according to IEC 61850. Therefore, the engineering work done

remains memorised and can be reused at any

time for adaptations, extensions and also refurbishment.

- The requested standard and compliance

with IEC 61850

A prerequisite for reasonable project execution is the use of components (IEDs -

Intelligent Electronic Device), which are

proven to be compliant with IEC 61850. The framework for the compliance test is given in

part 10 of the standard (IEC 61850-10) and is

now being detailed by user organizations and test bodies. A test certificate has to be supplied.

The main compliance features are the data

model according to the implemented functions

and the proper running of the needed and

specified services. It shall also be mentioned

that each compliant IED has to be supplied

with a formal data sheet being the SCL

description of its capabilities (ICD - Interface

Control Document files).

3. IEC 61850 FOR SCADA APPLICATION

IN SUBSTATIONS

3.1 Tasks

SCADA - Supervisory control and data

acquisition is one of the basic tasks of a

substation automation system. The tasks of

SCADA are:



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Fig.3 Data model and naming

Local and remote operation of the

switchgear and another equipment.

Acquisition of switchgear information and

measurments.

Handling of events and alarms.

The SCADA application is related to human operation of the network and is performed by a

local or remote operator. The data

communication for this application is directed vertically, i.e. from a higher control level down

to a lower one (commands of any kind from the

operators place) or reverse (binary indications

like breakers or isolators position, measurands

from instrument transformers...) as Figure 2.

3.2 Model (fig.2)

The vertical relationship IEC 61850 is using

the client - server concept. The server is the process or bay level (IEDs), which provides all

data to the client at station or remote level. The

data are provided on request by the server or

automatically by a report from the server issued

if certain conditions are fulfilled. The client is

mostly a computer representing the operators

work place. The client can send commands to

the server for changing data in the server to:

Issue commands for the operation to the

switchgear.

Modify the behavior of the server through

the change of internal data (e.g. change of

parameter sets, analog set-points, enabling or disabling functions).

In a client-server communication, the client controls the data exchange. Therefore, client-

server communication is very flexible in terms

of the data to be transmitted. Compared to a

master slave system, the client-server concept

allows the implementation of multiple clients in

the same system. (e.g. the gateway and the HMI

- Human Machine interface are clients).

IEC 61850 not only specifies the method of the data transfer but also defines the process

data of the servers. For that purpose, IEC 61850

uses an object-oriented approach with Logical Nodes (LN) as core objects. A logical node is a

functional grouping of data and represents the

smallest function, which may be implemented independently in devices. Examples Logical

Node XCBR contains group data of circuit

breaker or Logical Node PTOC is the data of a

timed overcurrent protection.

Logical Nodes have object data, and object-data have data attributes. For example, the

XCBR (Q0_XCBR) has a data called Pos, with

one attribute stVal, which indicates the

position (values according the common double

point indication: off, on, intermediate-state,

bad-state) and another attribute ctlVal for the opening and closing command (values: off, on).

Logical Nodes are grouped in Logical Devices.

Example: Logical Device Tampa_Protection for two zone distance protection Logical Node

PDIS per zone (PDIS1 and PDIS2 in Fig.3).

Logical Devices are implemented in physical

Fig.2 Vertical comminication in the substation

automation system



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Fig.4 Horizontal comminication in the substation

automation system

devices (IEDs). There is some actual information needed not only about the Logical

Nodes and Logical Devices but also about the

complete IED like the status of the common power supply. This information is modeled in

the Logical Node LPHD (see Error! Reference

source not found.3).

3.3 Application

A typical application of SCADA is the

creation of alarm and event lists. With IEC

61850, datasets used together with the report service can be used for that purpose. As an

example, a utility may specify a dataset per IED

that contains all data for the alarm list. The NCC gateway provides the interface from the NCC

(National Control Center) to the substation. It

has two basic tasks:

Protocol and data conversion

Data collection

For the data collection, the NCC gateway is a

client in the IEC 61850 based substation

automation system. The data is typically

collected using the report model. The dataset

used in that case corresponds to the traditional

signal list specifying the information from the

substation to be transmitted to the NCC.

4. IEC 61850 FOR TIME CRITICAL

INFORMATION EXCHANGE

4.1 Tasks

There are several functions in the substation

automation system, which require a time critical

exchange of binary information between

functions located within the same bay or in

different bays. Examples:

Exchange between line protection and

autorecloser.

Exchange between bays for breaker

failure.

Exchange between bays for station

interlocking.

Typically, these functions are not using human interaction and are time critical. They are

time critical because they are safety critical. The

maximal accepted communication delay is in the range of several milliseconds. This information

exchange is a horizontal communication

between devices at the same hierarchical level

(Fig.4).

4.2 Model

As an example, for the information exchange

between the protection function and the breaker failure function, the following logical nodes are

involved:

PTRC (protection trip conditioning)

representing the logic in a protection device

that creates the binary outputs (start and trip

output of e.g. the line protection device).

RBRF representing the protection related

function Breaker Failure function.

The information exchange between these

logical nodes is also modeled as data. The data

is part of the logical node that is the source of

the information exchange. As example, the LN

PTRC has a data Tr with an attribute general

representing the trip output of the protection

device for a general trip. That signal is not only

used to operate the breaker, but it also is used to trigger the breaker failure function.

For the exchange of this type, IEC 61850

introduces a specific information exchange

service called GOOSE (Generic Object Oriented



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Fig.5 Connection between distance protection

and recloser functions

Substation Event) based on the publisher-subscriber concept. The content of a GOOSE

message is defined with a dataset (similar like

for the report model described above). The GOOSE message is sent as a multicast message

over the communication network. That means

that multiple devices can receive the message

and retrieve the information required from the

message. The communication service is not

confirmed; instead, the message is repeated

several times.

In the example of the breaker failure function

a GOOSE message is configured in the protection device that contains at least the data

PTRC.Tr.general. As soon as

PTRC.Tr.general changes its the value to

TRUE, the GOOSE message is sent. The device

performing the breaker failure function is

receiving this message and detects that

PTRC.Tr.general has changed its value to TRUE. Another GOOSE message is sent when

the value changes back to FALSE.

4.3 Application

There are two types of application,

depending if the exchange of information is

between devices inside the bay or between

devices placed in different bays.

Exchange of information inside the bay: A

typical example is the exchange of information between Logical Device Distance Protection

containing instances of LN PDIS, LN PTRC and

the Logical Device Recloser containing the LN RREC in case these both functions are

installed in separate devices as Fig.5.

The LD Distance Protection sends

information to the LD Recloser: start of

starting elements in LN PTRC (PTRC.Str) and

trip in LN PTRC (PTRC.Op). Based on these

information and depending on the settings

(single pole recloser or three pole recloser;

RREC.TrMod) the recloser function

represented by RREC will send information

(RREC.TrBeh) to the LD Distance Protection in order to enable the expected trip

(if one or three phases PTRC.Tr) to the breaker.

The open command to the breaker is issued by the recloser function (RREC.Op).

5. IEC 61850 FOR SUBSTATION

AUTOMATION DESIGN

Substation automation designs have many

steps from the specification up to the

commissioning of a project specific system. SCL was introduced for a comprehensive

description of the complete substation

automation system supporting the goal interoperability of the standard. The description

in SCL allows:

single line diagram,

function allocation to the single line

diagram,

function allocation to devices,

data as being mandatory and optional

according to IEC 61850 (optional if needed or provided),

connection in the communication system,

setting of all configuration parameters as

defined in IEC 61850.

To use IEC 61850 for building the substation

automation, the system designer need:

- ICD files of IEDs

- SSD files of system



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Fig.6 Engineering process using SCL files

The capabilities of an IEC 61850 compliant

device are described in an IED Capability Description (ICD) file. A vendor of devices

claiming conformance to IEC 61850 has not

only to supply paper documentation like a data

sheet but also an ICD file.

The SSD file is used to describe the single line diagram and the allocated functions. The

optional data that need to be supported can also

be described in the SSD file. This replaces the traditional signal list, the elements of a signal

list being the data of LNs. Any system

integration tool needs the SSD file and the ICD files of all devices of the system. The output is

the Substation Configuration Description (SCD)

file. For maintenance and future system

modifications the SCD files have to be archived

as part of the project documentation.

The system configuration tool will take these files written according to SCL and merge these

by the system engineering process to a SCD file.

The formal SCL description will result in a consistent data exchange, allow exchanges

between compliant tools independent from the

supplier and, finally, in a machine-readable

documentation of the data and communication

structure of the SA system. Any extension or update in the future will not start from the

scratch but from the archived SCD file.

6. CONCLUSION

IEC 61850 is efficient standard in building

protection and control automation in the

substation. It provides not only a powerful

method to reach interoperability, but also

supports to cover all aspects related to the

communication, naming, engineering capabilities, conformity, testing... in Substation

Automation Systems, optimized solution

exploiting all benefits for users.

It doesnt mean that all delivered IEC 61850

systems will have the same quality independently of the manufacturer because

architecture remains free as architecture of the

communication system as well as location of the

different functionality as well as the quality of

each protection functions. The first experiences

done by manufacturers and utilities have now to confirm if the expectations are fulfilled and if

some extensions inside the standard will be

needed.

REFERENCES 1. Klaus-Peter Brand, Christoph Brunner, Ivan

De Mesmaeker. How to use IEC 61850 in

protection and automation. Baden and

Zrich, Switzerland, 2005.

2. De Mesmaeker Ivan - CIGRE. Protection and

substation automation systems: handling of

standardisation, integration and information technology. ABB Switzerland, 2006.

3. De Mesmaeker Ivan, Klaus-Peter Brand,

Peter Rietmann, Petra Reinhardt. Practical considerations in applying IEC 61850 for

protection and substation automation

systems. Baden and Zrich, Switzerland,

2005.

advantage of iec 61850

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