PTL Items PSB and Tripping ANS 11007 ENU

8/13/2019 PTL Items PSB and Tripping ANS 11007 ENU

1/17

OMICRON Page 1 of 17

Application Note

Extending existing PTL Items for Distance Protectionwith Power Swing Blocking and Tripping Tests

AuthorOliver Janke |[email protected]

DateApr 19, 2011

Related OMICRON ProductCMC Test Set, Test Universe

Application AreaLine Protection with Distance Protection

KeywordsPower Swing, NetSim, PTL

Versionv1.0

Document IDANS_11007_ENU

Abstract

This document shows how to extend existing PTL items. The OMICRON Test Module NetSimwill be usedfor testing the power swing blocking function during stable power swings and the tripping function duringunstable swings.
mailto:[email protected]:[email protected]:[email protected]:[email protected]


2/17

OMICRON 2011 Page 2 of 17

Content

1 Introduction ..................................................................................................................................... 3

2 The Emergence of Power Swings and their Detection .................................................................. 3

3 The OMICRON Protection Testing Library (PTL) ........................................................................... 53.1 The Structure of the XRIO Converter ........................................................................................ 53.2 Using the Import Filter ............................................................................................................... 6

4 Adding a NetSim Module for Power Swing Blocking ..................................................................... 6

5 Adding a NetSim Module for Power Swing Tripping ....................................................................11

6 Tips for Defining a Good Test Case ..............................................................................................13

7 Testing Power Swing Detection of ABB REL670 and Siemens 7SA631 ......................................147.1 Testing Power Swing Blocking of ABB REL670 ........................................................................14

7.2 Testing Power Swing Blocking and Tripping of Siemens 7SA631 .............................................15

Please use this note only in combination with the related product manual which contains several important safetyinstructions. The user is responsible for every application that makes use of an OMICRON product.

OMICRON electronics GmbH including all international branch offices is henceforth referred to as OMICRON.

OMICRON 2011. All rights reserved. This application note is a publication of OMICRON.

All rights including translation reserved. Reproduction of any kind, for example, photocopying, microfilming, opticalcharacter recognition and/or storage in electronic data processing systems, requires the explicit consent of OMICRON.Reprinting, wholly or in part, is not permitted.

The product information, specifications, and technical data embodied in this application note represent the technicalstatus at the time of writing and are subject to change without prior notice.

We have done our best to ensure that the information given in this application note is useful, accurate and entirelyreliable. However, OMICRON does not assume responsibility for any inaccuracies which may be present.OMICRON translates this application note from the source language English into a number of other languages. Anytranslation of this document is done for local requirements, and in the event of a dispute between the English and a non-English version, the English version of this note shall govern.


3/17


1 Introduction

The OMICRON Protection Testing Library(PTL) provides predefined test plans (Protection TestingTemplates, PTTs) for testing a number of relays including distance protection devices. The respective PTLitem supports the test person in developing a high quality test for the main protection functions in a shorttime. But for different reasons power swing detection is not implemented in the PTL. The aim of thisapplication note is to demonstrate how the OMICRON Test Module NetSimcan be added to an existing PTTto test this function. This is shown for the following three distance protection relays:

> AREVA P442

> ABB REL670

> SIEMENS 7SA631

NetSimwill be used to simulate the transient processes in a power network during a power swing to analyzethe protection devices reaction. The whole protection system and not setting parameters is tested thereby.This kind of testing is called system testing. It proofs whether the IED (Intelligent Electronic Device) willprotect the electrical equipment in the specific case, or not.

Also other test modules like the OMICRON State SequencerModule or the OMICRON Rampingmodule canbe used for this purpose, however this is not content of this document. You can find other application notesabout this topic on the OMICRON website.

2 The Emergence of Power Swings and their Detection

During the normal operation of the electrical power network the actual load always equals the generation.But caused by sudden load changes, switching operations or faults this balance can be disturbed. Becauseof the inertia of all connected electrical machines and the slow control of the generation of active powerthese events result in oscillations of voltages and currents. There are two possible scenarios:

1. The control devices are able to dampen the oscillations and the power system is equilibrated again. Wecall that a stable power swing.

2. One or more generators fall out of step and loose synchronism to the remaining network. This is called anunstable power swing.

During this process the installed distance protection relays measure impedances that can be similar to thoseduring three phase faults (seeFigure 1). If the impedance is within a tripping zone for a long enough time,the protection device will trip the circuit breaker to disconnect the electrical equipment. During the first casetripping is not needed as no fault exists on the network and the disturbance will disappear by itself. To solvethe disturbance in the second case a few predefined connections within the network should break before thewhole network splits in separate subnetworks. To define these locations several considerations have to bemade. An activated power swing detection can prevent these non selective trips and thus possible blackoutslike the Northeast Blackout of 2003 in North America.


4/17


Figure 1: Impedance trajectory during power swings

But how does the IED distinguish between a stable power swing, an unstable one and a fault? While theimpedance change during a power swing is rather slow the impedance vector jumps directly into the trippingzone at a fault occurrence. At a stable power swing the measured impedance enters the zones from oneside, then turns around and leaves at the same side (seeFigure 1). During an unstable power swing theimpedance crosses the X axis completely and leaves the zones on the other side.

The relay manufacturers developed different algorithms to decide which case is present. They all use one ormore of the following criteria:

> Power swing detection zone: AsFigure 1 shows, a frame is drawn around the tripping zones or thestarting zones. If the impedance is calculated within this area for a given number of measurementcycles, it is recognized as slowly changing and thus a power swing. Another possibility is to determinethe time the trajectory needs to move through this area. Position and size of this frame are importantparameters and can be set for some protection devices.

> Monotony: The movement direction in R and X is determined. During a power swing only one direction ischanging.

> Continuity: The measured impedance must be changing with at least a minimum value to ensure, thetrajectory is moving. Otherwise it cannot be a power swing.

> Regularity: The ratio of two successive changes of the measured impedances is below a limit value. Thisensures that the trajectory moves with constant or slowly changing speed, but not performing rapidchanges.

> Out of step detection: It is proved from which side the trajectory enters and leaves the out of stepdetection zone (which can be the power swing detection zone or a similar one). Another criterion is thedirection of the impedance movement when crossing the line angle. Depending on the setting of the IEDit trips immediately or after a given number of turns.

Furthermore other criteria and exceptions to the listed ones are possible.

X

R

lineimpedance

stable power swing

unstablepower swing

power swingdetection zone

tripping zone


5/17


There are two different power swing functions in modern numerical relays:

> Power swing blocking: The whole distance protection or only assigned zones are blocked when a powerswing occurs.

> Power swing tripping: The relay trips after detecting an unstable power swing.

3 The OMICRON Protection Testing Library (PTL)

There are different sources for the PTL: It can be installed from the DVD or CDs that are shipped with theCMC test set or it can be downloaded from the OMICRON customer area (www.omicron.at). In both cases itis free of charge.

Each PTL item consists of several files:

> An *.xrio-file: This is the XRIO converter. It can be used as test object for every test module. Afterentering the actual relay settings, the converter calculates the characteristics for the main protectionfunctions automatically.

> An *.occ-file: This is the PTT (Protection Test Template) and consists of several test modules to test themain functions of the corresponding protection device. A test for power swing blocking or tripping isalways missing. The XRIO converter is already included as test object. Using the PTT is the fastest wayof using the PTL as only the relay settings and little other information have to be entered in the testobject.

> One or two *.pdf-files: These are the manuals for the PTL item. They contain important information onhow to use these files.

3.1 The Structure of the XRIO Converter

Each PTL XRIO converter is divided in five sections:

> Relay Parameter Section:This is a copy of the relay settings software. The actual settings of thedevice have to be entered her either manually or with the help of an import filter (see chapter0). Also thesettings for the power swing detection are included, even if this function is not supported by the PTT.They can be used to build a customized test for this function.

> Additional Information:This block contains few parameters which are needed to test the device butare not part of the relay settings.

> RIOplus:This part is used for calculations to convert the relay specific parameters to values valid for theRIO block and OMICRON Test Universe test modules. It is only visible if the advanced view of the XRIOeditor is active.

> Template Controller:This block is needed for the PTT. Only visible in advanced view.

> RIO:This block contains the resulting characteristics for most of the protection functions. Nothing mustbe changed here, as the formulas for the automatic calculation would be destroyed. In case of adistance protection the RIO function Distancecontains the zones. They will be used for testing thepower swing detection.
http://www.omicron.at/http://www.omicron.at/http://www.omicron.at/http://www.omicron.at/


6/17


3.2 Using the Import Filter

With the help of one of the OMICRON import filters the manual entry of settings may be omitted. Differentimport filter for different manufacturers are available. With the import filter and the specific relay parametersoftware export file, it is possible to import the relay settings automatically into the XRIO converter. Even if

the PTTs are normally not supporting power swing detection, the relay import filter will also work for thesesettings.

4 Adding a NetSim Module for Power Swing Blocking

In the following the PTT for AREVA P441, P442 and P444 is used as an example. After installing this PTLitem the PTT is opened and the settings of the relay are entered in the converter.

For testing the power swing blocking function a NetSim module is inserted after the last distance protectiontest, which is the SOTF (switch on to fault) test. At first the correct Test Caseat the menu Parametersmustbe selected (seeFigure 2). There are three different power swing cases:

> Synchronous: A stable power swing is simulated. This one is selected here.

> Asynchronous, Multiple Turns: An unstable power swing is simulated with multiple pole slips.

> Asynchronous, With Fault: An unstable power swing is simulated with multiple pole slips. Additionally afault occurs at a predefined time.

The impedance view (Figure 3)shows, that the module is automatically using the impedance characteristicdata of the converter. Also the three trajectories of the phase to phase impedances are drawn. With thedefault test settings entered in the test view (Figure 4)tabs the impedances will never reach the trip zonesand thus no power swing blocking can be tested. Therefore the according settings have to be adapted first.Some further understanding of the data of the actual network and the physics behind the power swing isneeded.

Figure 2: Selection of the Test Case


7/17


Figure 3: Impedance view

Most of the parameters which have to be entered in the Test Viewdo not correspond to the settings of theprotection function. Instead these are data about the network the IED is used on. By means of these datathe module will simulate the transient signals which occur during a power swing on this network. Not thesettings of the relay are tested, but its behavior under realistic conditions. Unfortunately some of the needednetwork data are often not available in practice. Furthermore most of the networks have a variety ofswitching states. This leads to many different combinations of test settings that have to be tested. But withsome considerations a good test case can be found. If there is no claim laid to test with real network data,there is still the possibility to test the protection function with the standard values.

So let's go through the test views tabs and see, which effect on the test the individual settings have.

FaultIn this tab a Prefault and a Postfaulttime can be set. 100 ms are enough for both. The next two settings are

much more important for the test:

The Slip anglespecifies the maximum asynchronicity. 180 are the theoretical limits for a stable powerswing. If the angle became even more, the machine would fall out of step, as its maximum torque wasexceeded. Less slip angle means less power swing and results in higher impedances. By entering themaximum of -180 it is achieved that the relay measures impedances within the tripping zones. The negativelimit is chosen as this will create a power swing coming from the right what looks like a big load to the IED.The protection device will thus be tested whether it is still working fine in such a difficult situation.

Figure 4: Test View with entered Fault settings


8/17


The Slip timedefines the duration of the power swing. If this time is too short the trajectory might move tofast and leave the tripping zones before the distance protection tripped. 500ms are a good value but after allsettings were entered it must be checked, that the trajectory stays within a tripping zone for a long enoughtime.

LineHere the LinkToXRIO function is used to define the lines parameters (seeFigure 5). For the selected modeZ and kthe corresponding values are stored in the RIO block of the converter (seeFigure 6). As they aresecondary values, this option must be selected in the Viewmenu before linking otherwise they areinterpreted as primary values. The value for the grounding factor must be checked, as some PTL convertersuse a grounding factor of zero and recalculate all zones to loop impedances. In that case the link must bedone to the corresponding parameter in the Relay Parameter Section. Changing the Mode might be needed.

Figure 5: Line settings

Figure 6: Linking the line settings

SourcesThese data are characterizing the network. A user defined block called "System Data" is added to the XRIOconverter for some calculations (seeFigure 8).

The Voltageand Frequencyin this tab (Figure 7)can be linked to the nominal values in the RIO Deviceblock.

Delta Vand Delta phiare both zero for the moment. Chapter6 explains how these values can be used tomove the trajectory of the impedances.


9/17


For the impedance magnitudes and angles a user defined XRIO block shall be used. This block must beadded to the XRIO converter like shown inFigure 8 and is used to calculate the source impedances,from the short circuit power ,of the two connected sources. To calculate the parameters

Z1 source 1and 2equation (1) is implemented as a formula in XRIO.

, =.,

,

,

,

(1)

In this equation ,is the primary nominal line to line voltage. The four variables above and below the

right fraction line are the primary and secondary values of the installed current transformers or voltagetransformers. They are needed to convert the impedance value to a secondary value.

The results can be linked to the NetSim settings Zmagfor source 1 and source 2. The angles can beentered either directly in NetSim or as seen inFigure 7 andFigure 8 also linked to XRIO. In the converterthe angle is calculated from an R/X ratio of 10%, which is an approximation that can be made if the exactvalues are not known. For this example 5000 MVA are used for both sources.

The grounding factor magnitudes and angles can normally be chosen as one and zero, if the exact values

are unknown.

Figure 7: The sources definition

Figure 8: The user defined block System Data in XRIO


10/17


OutputsThe primary and secondary values for the current transformers and voltage transformers can be linked to thecorresponding values in the RIO Deviceblock (seeFigure 9). This has only to be done for the location (A orB) at which the relay is installed.

Figure 9: The output configuration

After all settings have been entered the impedance view shows the resulting power swing (seeFigure 10).As a next step, the trajectories are proved to remain in a tripping zone long enough to evoke a trip. As thetrajectories move into Z1 (TZ1= 0 s) this zone will probably cause the trip. Depending on the movement

speed theoretically every other zone could trip first. To test the power swing blocking function at least onezone must be found that would surely trip, if the function did not work probably. Therefore the cursors aremoved on the time axis to find the points where the trajectories enter and leave the zone. It is even moreexact not to take the borders of the zone but to use the tolerance lines. Now the time deviation can be read,which is 110 ms what is enough for the relay to trip. The proper operation of the power swing blockingfunction can be tested with this power swing. If the time was too short the Slip Time(Fault settings) can beincreased.

Figure 10: Measuring the time the trajectory of the resulting power swing is within zone 1

cursor 1

cursor 2


11/17


After configuring the trip signal in the local hardware configuration three measurements for the phaseselective trip times can be defined. These time measurements start with the beginning of the power swingand end with the trip signal for phase A, B or C. When testing the power swing blocking function, no trip isexpected at all, that's why no nominal values are entered. Therefore the assessment must be donemanually. The test was OK if no trip occurred. The Measurement Viewafter a successful test is shown in

Figure 11.

Figure 11: Measurement View

5 Adding a NetSim Module for Power Swing Tripping

To test the power swing tripping function of the relay another NetSim module must be added, where

Power Swing / Asynchronous / Multiple Turnsis selected as test case. The settings are very similar to thosefrom the power swing blocking test:

Power SwingA Slip frequency(seeFigure 12)of 1 Hz causes a slow enough movement through the impedance plane, topossible cause a trip. The duration of each turn will be is 1 s and the trajectory will again move from right toleft through the impedance plane.

As the example relay is configured to block during the first turn and trip if a second one occurs, theNumber of turnsshould at least be two.

Figure 12: The Power Swing settings

Line, Sources and OutputsThese settings are exactly the same as for the power swing blocking test and can be seen inFigure 5,

Figure 7 andFigure 9.

The resulting impedance trajectory is shown inFigure 13.The time within zone 1 can be determined asabout 110 ms, what is long enough.


12/17


Figure 13: The resulting out of step power swing

Again measurements for the trip times are defined. Unlike during the power swing blocking test trips are nowexpected in all three phases. Defining a nominal time is not possible, as it depends on the moment the relayrecognizes, that the power swing is an unstable one, which in turn depends on the algorithm of the IED. Thistask is something completely different to measuring the trip time of a zone. The assessment again has to bedone manually.Figure 14 shows the result of this measurement: A trip time above 1 s signifies that the relaytripped as supposed during the second turn. This can be verified with help of the signal view.Figure 15clearly shows that all three trip signals occur during the second power swing. This is exactly how the IEDwas meant to react. Thus the power swing tripping function could successfully be tested that way.

Figure 14: Measurement for the trip time

Figure 15: Signal view of an unstable power swing


13/17


6 Tips for Defining a Good Test Case

A good test case for a stable power swing is one with the turning point of the trajectory inside of zone 1. Thiswill ensure that the relay will trip if the power swing blocking function did not work probably.

If the real network data (i.e. the source impedances) are unknown, default values have to be used orassumptions must be done.

If the resulting turning point is outside of all tripping zones there is a possibility to move it within theimpedance plane: By changing the value for Delta V(seeFigure 7)the transfer of reactive power on the linecan be modeled. With Delta phi the active power transfer can be changed. This results in a movement of theturning point like shown inFigure 16.A change of reactive power results in a movement in direction of theline angle, a change of active power in a movement in 90 turned to it.

These two parameters can now be used to move the turning point from outside of the tripping characteristicto the inside. Of course only realistic values should be used, that correspond to a power transfer that canhappen in reality. Nevertheless this function can still be tested by using unrealistic test values that do not

represent the connected network.

Figure 16: Movement of the turning point depending on the power transport

X

R

line impedance

-Delta V

+Delta V

-Delta phi

+Delta phi

line angle


14/17


15/17


Figure 18: Power swing blocking test for ABB REL670

7.2 Testing Power Swing Blocking and Tripping of Siemens 7SA631

In the example settings for this relay power swing blocking and tripping are activated. It is configured to havephase selective trip signals. Therefore both NetSim modules from the Areva P442 test can be copied to theSiemens 7SA631 PTT. But before that the System Datablock must be added to the converter like in theprevious chapter. The modules will now automatically use these values and also the distance characteristicof the RIO block. Again the links for the line settings must be adapted to the new settings: Like inFigure 19 adifferent mode must be selected. The RandXvalues can be taken from the RIOplusblock underProtectedObject. The two ratios RE/RandXE/Xare linked to the RIO distance function.

For testing power swing tripping the number of turns is changed, as the IED is meant to trip during the firstpole slip.Figure 20 shows the resulting trajectory. After checking its residence time within zone 1 the test

can be started.

Figure 19: Line settings for Siemens 7SA631


16/17


Figure 20: Testing of power swing tripping of Siemens 7SA631

List of Literature

[1] Michael Albert, Eugenio Carvalheira, Oliver Janke: PTL: A solid basis for building customized lineprotection test standards, OMICRON IPTS 2009 (www.omicron.at)

[2] Dr. Peter Meinhardt, OMICRON electronics GmbH: Testing approaches for power swing blockingfunction, OMICRON IPTS 2009 (www.omicron.at)

[3] Dr. Fred Steinhauser, OMICRON electronics GmbH: Testing of the Power Swing Blocking inDistance Relays

[4] Dr. Yuchen Lu, Dr. Juergen Holbach, Laurie Martuscello, P.E., Edward Krizauskas, P.E.: Tests ofDistance Relay Performance on Stable and Unstable Power Swings Using Simulated Data of theAugust 14th 2003 System Disturbance

[5] Jrg Blumschein, Matthias Kereit, Yilmaz Yelgin, SIEMENS: Erhhung der Netzstabilitt durchzuverlssige Pendelerkennung, Tagungsbeitrag 4.1 OMICRON Anwendertagung 2009

(www.omicron.at)

[6]MiCOM P441/P442/P444 Numerical Distance Protection, Technical Manual

[7] Technical reference manual Line distance protection IED REL 670

[8]SIPROTECDISTANZSCHUTZ 7SA6MANUAL
http://www.omicron.at/http://www.omicron.at/http://www.omicron.at/http://www.omicron.at/


17/17

OMICRONis an international company serving the electrical power

industry with innovative testing and diagnostic solutions. The application of

OMICRON products provides users with the highest level of confidence in

the condition assessment of primary and secondary equipment on their

systems. Services offered in the area of consulting, commissioning,

testing, diagnosis, and training make the product range complete.

Customers in more than 140 countries rely on the company's ability to

supply leading edge technology of excellent quality. Broad application

knowledge and extraordinary customer support provided by offices in

North America, Europe, South and East Asia, and the Middle East,

together with a worldwide network of distributors and representatives,

make the company a market leader in its sector.

Europe, Middle East, Africa

OMICRON electronics GmbH

Oberes Ried 1

6833 Klaus, Austria

Phone: +43 5523 507-0

Fax: +43 5523 507-999

[email protected]

Asia-Pacific

OMICRON electronics Asia Limited

Suite 2006, 20/F, Tower 2

The Gateway, Harbour City

Kowloon, Hong Kong S.A.R.

Phone: +852 2634 0377

Fax: +852 2634 0390

[email protected]

Americas

OMICRON electronics Corp. USA

12 Greenway Plaza, Suite 1510

Houston, TX 77046, USA

Phone: +1 713 830-4660

+1 800-OMICRON

Fax: +1 713 830-4661

[email protected]

For addresses of OMICRON offices with customer service

PTL Items PSB and Tripping ANS 11007 ENU

Documents

Transcript of PTL Items PSB and Tripping ANS 11007 ENU