functional testing of sas-areva article

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Study Committee B5 Colloquium2005 September 14-16

Calgary, CANADA

FUNCTIONAL T ESTING OF IEC 61850 BASED SUBSTATI ON

AUTOMATION SYSTEMS

Benton Vandiver, OMICRON electronics Corp USA

Alexander Apostolov, AREVA T&D Automation, USA

KEYWORDS: IEC 61850, Substation Automation Systems, Functional Testing

1. INTRODUCTION

The integration of multifunctional Intelligent Electronic Devices in complex substation or

power plant automation systems requires the development of a standard protocol that willmeet the requirements of protection, control, monitoring, recording and metering functions.

The new IEC 61850 standard for communication networks and systems in substations allows

the development of high-speed peer-to-peer communications based applications, as well as

distributed metering, control and protection solutions based on multicast analog data or

sampled analog values.

The paper discusses in detail the requirements for functional testing of complex substation

automation systems. Two typical types of IEC 61850 based Substation Automation Systems

(SAS) are considered:

• A system with Substation Bus (IEC 61850-8-1) only

• A system with Process Bus (IEC 61850-9-2) and Substation Bus (IEC 61850-8-1)

The method for testing of both types of systems is proposed based on the following order of

system components tests:

• Testing of IEC 61850 protocol compliance of the individual components of the system –

IEDs, client applications, etc.

• Functional testing of Merging Units

• Functional testing of IEC 61850 compliant IEDs

• Functional testing of bay level distributed applications

• Functional testing of substation level distributed applications

Requirements for configuration of test plans for local and distributed functions and how the

Substation Configuration Language defined in the standard can help automate that process

are discussed.

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Solutions for the testing of the individual components of the IEC 61850 based system, as well

as for the testing of distributed applications are described in detail.

2. DISTRIBUTED APPLICATI ONS IN IEC 6185 0 BA SED SAS

IEC 61850 defines functions of a substation automation system related to the protection,

control, monitoring and recording of the equipment in the substation. These functions can beexecuted within a single physical device (for example a protection IED) or can be distributed

between multiple devices using a hard-wired or communications interface.

The functions in the substation can be distributed between IEDs on the same, or on different

levels of the substation functional hierarchy (Station, Bay/Unit or Process)

These levels and the logical interfaces that IEC 61850 focuses on are shown in Figure 1.

Fig. 1 Logical interfaces in Substation Automation Systems

Technical Services

Remote control (NCC)

CONTR. PROT.

FCT. A FCT. B

PROT. CONTR.

Sensors Actuators

BAY/UNIT LEVEL

STATION LEVEL

PROCESS LEVEL

HV Equipment

Remote

rotection

Process Interface

1,6

3 3

9

8

1,6

2 2

4,54,5

710

Remote

protection

Distributed applications in SAS are typically based on two of these interfaces defined as:

IF4: CT and VT instantaneous data exchange (samples) between process and bay level

IF8: direct data exchange between the bays especially for fast functions like interlocking

Functions in the substation can be divided into sub-functions and functional elements. The

functional elements (Logical Nodes) are the smallest parts of a function that can exchange

data. In the case when a function requires exchange of data between two or more logical

nodes located in different physical devices, it is called a "distributed function". It is clear that

when we test a SAS and its related components, we need to perform tests starting from the

Logical Nodes and going all the way up to the distributed applications hierarchy in order to

complete the distributed function testing.

The exchange of data is not only between functional elements, but also between different

levels of the substation functional hierarchy. It should be kept in mind that functions at

different levels of the functional hierarchy can be located in the same physical device, and at

the same time, different physical devices can be exchanging data at the same functional level.

As can be seen from Figure 2; a Logical Connection (LC) is the communications link

between functional elements - in this case Logical Nodes of the P and R groups. IEC 61850

also defines interfaces that may use dedicated or shared physical connections - the

communications link between the physical devices.

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The allocation of functions between different physical devices defines the requirements for

the physical interfaces, and in some cases may be implemented into more than one physical

LAN.

Bay

computer

Distributed

function

IF 8LC1

P..

R...LC2

Protection

IED

IF 8

Protection

IED

P...

R...

P...

Fig. 2 Distributed Function definition in IEC 61850

3. CONFIGURATI ON REQUI REMENTS FOR TESTIN G OF SAS

One of the key requirements for testing of IEC 61850 based devices and SAS is to ensure

interoperability and a seamless integration process. Interoperability is defined as the ability of

two or more IEDs from the same or different vendors to exchange information seamlessly

and use that information for correct internal/external operation. This is commonly referred to

as “plug-n-play” in the personal computer industry.

Before the functional testing of a device or distributed function is started, they need to passthe conformance tests define in the standard. (Part 10 of IEC 61850 defines these

requirements.) For a device to be acceptable for integration in an IEC 61850 SAS it first has

to be properly type tested. This will ensure that it is compliant with the definitions of the

standard and will likely interoperate with other certified IEDs in the system. Since

conformance testing is not the subject of this paper, all devices described are considered

compliant.

Part 6 of the standard defines the Substation Configuration Language (SCL) and provides

some tools that can be very helpful in performing automatic functional testing. One difficulty

is to determine the functionality of the tested device and its configuration (which functional

elements are enabled and what are their settings). Help in automating this process will result

in significant timesavings. The SCL is basically a system specification of the substationequipment connections in a single line diagram. It also documents the allocation of Logical

Nodes to devices and equipment of the single line to define functionality, access point

connections, and sub network access paths for all possible clients.

What is of specific interest for the automatic test configuration is the data exchange between

the system configuration tool, the tested IED configuration tools, and the test system

configuration tool shown in Figure 3.

The overall functionality of any IEC 61850 compliant device is available in a file that

describes its capabilities. This file has the extension “ICD” meaning IED Capability

Description. The system specification tool supplies to the system configuration tool

information such as the single line diagram of the substation and the required logical nodes.

The file extension for this file is “SSD” meaning System Specification Description.

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The system configuration tool then provides information to the IED configuration tools

regarding all IEDs, communication configuration and substation description sections. This

information is in a file with the “SCD” extension meaning Substation Configuration

Description. This information also needs to be provided to the functional testing tools in

order to allow it to configure the set of tests to be performed.

IEC 61850Standard IED

Configuration Tool

IEC 61850Based

IED

IEC 61850Standard SystemConfiguration Tool

IEDDB

IEC 61850Functional

TestingTool

Test Device

Fig. 3 Functional testing configuration process

The Standard IED configuration tool sends information to the IED upon its instantiation

within a SAS project. The communication section of the file contains the current address of

the IED. The substation section related to this IED may be present and then shall have name

values assigned according to the project specific names. This file has an extension of “CID”

meaning Configured IED Description. Currently there is ongoing work to expand the content

of this file to include all settings, thus providing the required configuration data for both theIED itself, and also for the functional testing tool.

All the information on the substation, SAS, and IEDs configuration is required to properly

configure the test procedures for the functional elements and local/distributed functions.

However, even this is not sufficient for automating the process. Another important

requirement is to provide test cases on how each of the functional elements or

local/distributed functions should be tested and what is the expected behavior of the test

object under defined test conditions. Based on this information and the system/IED

configuration data a functional testing tool can generate and execute the necessary test

sequences. Unfortunately, such formal definition of the test cases for the functional elements

and other complex functions is not part of the standard today. Making functional test case

definitions part of the standard will require a significant effort, but will allow thedevelopment of new tools for automatic functional testing of IEC 61850 based IEDs and

SASs.

4. FUNCTIONAL TESTING OF IEC 61850 -BASED APPLICATI ONS

The testing of conventional functions in substation protection and control systems has some

similarities and some differences with the IEC 61850 communications based solutions. In the

case of the conventional testing, the test device has to simulate the substation process using a

hard-wired interface between the analog and binary outputs of the test device and the analog

and binary inputs of the test object. A typical test process requires the test device to output a

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simulation or event that will trigger a measurable response from the test object. Timing of the

test objects I/O change of state events for defined test cases determines proper operation.

By comparison, communications based distributed functions utilize the IEC 61850 GSSE or

GOOSE messages replacing the hard-wired connections. In the case of Fig. 4, all devices

with communications interface have to be connected to the substation network switch to

exchange data.The expected communications based performance should be similar to the conventional hard-

wired interface; it is a good idea to include a test case that compares the operation of a wired

relay output and a GSSE message driven by the same functional element in the IED logic.

IEC 61850

Based IED

V I

Ethernet

Ethernet

Switch

Laptop

Computer

Ethernet

Fig. 4 IEC 61850 GSSE or GOOSE based IED functional testing

Another difference between the conventional testing and the IEC 61850 GSSE based

functional testing is the requirement for the change-of-state process simulation using GSSE

messages from the test device to the test object. An example is to indicate the opening of theauxiliary contact 52a of the circuit breaker monitored by the IED under test.

GOOSE

or GSSE

GOOSE

or GSSE

Trip

IEC 61850

Based Test

Device

V I

EthernetSwitch

LaptopComputer

Ethernet

GOOSE

or GSSE

GOOSEor GSSE

Trip

IEC 61850 BasedTest Device

IEC

61850

BasedMU

IEC

61850

BasedIOU

IEC

61850

BasedIED

Fig. 5 IEC 61850 based IED functional testing results

Distributed applications based on IEC 61850 Merging Units that send sampled values over

the substation LAN will need a test setup similar to the configuration shown in Fig. 5.

In this case the analog signals from the test device will be wired to the Merging Unit. The

distributed function will be performed by the IEC 61850 based IED that will send a GSSE

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message to an IEC 61850 Input/Output Unit (IOU) that will operate a physical relay output to

trip the circuit breaker. The test device will subscribe and capture this message and also

detect the operation of the binary output of the IOU. It monitors different elements of the

distributed function and can analyze their performance, as well as the system’s overall

operating time.

If the tested 61850 based IED also has a binary output, the test device can monitor it as well.This can provide valuable information in the overall evaluation of process performance.

The binary output of the interface unit (IOU) will give the total distributed function operating

time for the case of a complete IEC 61850 communications based solution.

5. CONCLUSIONS

The development and implementation of IEC 61850 based devices and Substation

Automation Systems require a new generation of specialized test devices and methods to test

them. The use of the different configuration files defined in Part 6 of the standard and the

addition of the complete IED configuration information will allow the development of new

tools for complete automatic functional testing.

Simulation of the substation process and monitoring of the operation of the tested devices or

distributed control and protection functions is quite different from conventional testing. The

testing of IEC 61850 based applications require partial hard wiring between the test device

and the test object, and in some cases (with MUs) may be completely communications based.

Different testing configurations are analyzed and show that state-of-the-art test systems can

be successfully implemented for the functional testing of IEC 61850 based control and

protection functions with different levels of communications implemented.

SUMMARY (to be t ransla t ed in French)

The development and implementation of IEC 61850 based devices and substation automation

systems requires a new generation of specialized test devices and methods for functional

testing of different components of the system.

The paper discusses the requirements for functional testing of complex substation automation

systems. Two typical types of IEC 61850 based Substation Automation Systems (SAS) are

considered:

• A system with Substation Bus (IEC 61850-8-1) only

• A system with Process Bus (IEC 61850-9-2) and Substation Bus (IEC 61850-8-1)

The use of the different configuration files defined in part 6 of the standard and the addition

of the complete IED configuration information will allow the development of systems for

complete automatic functional testing.

Simulation of the substation process and monitoring of the operation of the tested devices or

distributed control and protection functions is quite different from conventional testing. The

testing of IEC 61850 based applications requires partial hard wiring between the test device

and the test object, and in some cases (with MU) may be completely communications based.

Different testing configurations are analyzed and show that state-of-the-art test systems can

be successfully implemented for the functional testing of IEC 61850 based control and

protection functions with different levels of communications implemented.

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functional testing of sas-areva article

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