Distance Teleprotection omicrn

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© OMICRON Page 1 of 24

Application Note

Application-oriented testing of a distance teleprotectionfunction end to end in the field using the correspondingRelaySimTest template

Author

Jens Baumeister | [email protected]

Date Feb 28, 2014

Related OMICRON ProductCMC - RelaySimTest

Application AreaDistance teleprotection end to end testing

KeywordsRelaySimTest, application-oriented testing, distance teleprotection, end to end testing, GPS synchronization,

PTP

Versionv1.1

Document ID

ANS_14004_ENU

Abstract

Due to the increasing complexity of our electrical power systems, the need for highly selective protection is

increasingly being fulfilled by the use of distance teleprotection. To test a teleprotection functionthoroughly, a distributed end to end test with synchronized injection can be utilized.

This application note describes how this could be done in an easy and comfortable way using thecorresponding OMICRON RelaySimTest test template. RelaySimTest offers simulation based system testingmethods. To perform a test a fault scenario is calculated based on the simulation of the power systemnetwork. The resulting voltages and currents for the different relay locations can be used to test the correctbehavior of the distance teleprotection system. For this reason RelaySimTest offers the possibility to controlseveral distributed and time synchronized CMC test sets.


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© OMICRON 2014 Page 2 of 24

General information

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

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.

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.

© OMICRON 2014. All rights reserved. This application note is a publication of OMICRON.


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Content

1 Safety instructions .......................................................................................................................... 4

1.1 Requirements to use this application note ................................................................................. 4

1.2 Safety instructions for this application note ................................................................................ 4

2 Introduction ..................................................................................................................................... 5

2.1 What this application note describes ......................................................................................... 5

2.2 Distance teleprotection ............................................................................................................. 5

3 System under test ........................................................................................................................... 7

3.1 Application example - protected line and time grading ............................................................... 7

3.2

Settings of the system under test menu in RelaySimTest .......................................................... 8

4 Test cases.......................................................................................................................................10

4.1 Application example – grid topology .........................................................................................10

4.2 Suitable test cases ...................................................................................................................11

4.2.1 Test case 1 – double infeed, fault on line .................................................................................... 12

4.2.2 Test case 2 and 3 – double infeed, line fault at 0 and 100%, RF and load current....... ...... ...... ...... 12

4.2.3 Test case 4 and 5 – single infeed, fault on line (weak infeed logic test) ...... ...... ...... ...... ...... ...... .... 14

4.2.4 Test case 6 and 7 – single infeed, fault on busbar ....................................................................... 15

4.2.5 Test case 8 and 9 – double infeed, fault on busbar, RF and load current......... ...... ...... ...... ...... ..... 15

4.2.6 Test case 10: time grading without teleprotection ........................................................................ 16

4.3 Measurement and assessment ................................................................................................16

5 Test sets configuration ..................................................................................................................18

5.1 Test setup................................................................................................................................18

5.2 The Test sets configurations in RelaySimTest and the Test Set Remote Agent ........................19

6 Performing the test ........................................................................................................................22

List of literature ..............................................................................................................................23


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1 Safety instructions

1.1 Requirements to use this application note

This application note may only be used in combination with the relevant product manuals which contain allsafety instructions. The user is fully responsibility for any application that makes use of OMICRON products.

Instructions are always characterized by a symbol even if they are included to a safety instruction.

DANGER

Death or severe injury caused by high voltage or current if the respectiveprotective measures are not complied.

Carefully read and understand the content of this application note as well asthe manuals of the involved systems before starting its practical application.

Please contact OMICRON before you continue the process if you do not

understand the safety instructions, operating instructions, or parts of it. Follow each instruction mentioned there especially the safety instructions

since this is the only way to avoid danger that can occur when working athigh voltage or high current systems.

Furthermore, only use the involved equipment according to its intendedpurpose to guarantee a safe operation.

Existing national safety standards for accident prevention andenvironmental protection may supplement the equipment’s manual.

Only experienced and competent professionals that are trained for working in high voltage or high currentenvironments may perform this application note. Additional the following qualifications are required:

• authorized to work in environments of energy generation, transmission or distribution and familiar withthe approved operating practices in such environments.

• familiar with the five safety rules.

• good knowledge of the CMC test system.

1.2 Special safety instructions for the application note

DANGER

Death or severe injury caused by high voltage or current.

Always turn off each system involved to the test process before wiring up orrewiring the equipment.

NOTICE

Equipment damage or loss of data possible.



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2 Introduction

2.1 What this application note describes

The application note describes the End to end relay tests of the RelaySimTest predefined DistanceTeleprotection template. Therefore it covers the following content of the test template.

1. Distance teleprotection (general information)

2. System under test

3. Test cases

4. Test sets configuration

The application note doesn’t describe a distance protection test itself. It doesn’t describe reach tests for thedistance zones, single end tests, wiring checks and parameter tests. To test the protection thoroughly suchtests are also recommended.

2.2 Distance teleprotection

The zone grading of distance protection has the problem that zone 1 (Z1) does not protect the entire lengthof the line. This means that instantaneous tripping is only possible for around 80% to 90% of the line (seeFigure 1).

Figure 1: Fault in zone 2


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If a fault occurs, communication between both sides of the protected line allows instantaneous tripping forthe entire line. This scheme is generally referred to as "teleprotection".

Figure 2: Functional principle of teleprotection: Fault between the teleprotection system (left side); Fault behind substation B (right side)

Figure 2 describes the principle of teleprotection:

> Left side: The fault is in zone 2 (Z2) for relay A and in Z1 for relay B. Relay B usestelecommunication to show relay A that the fault is between them. This allows relay A to tripinstantaneously, it doesn’t has to delay the tripping with the time of Z2.

> Right side: The fault is behind substation B. For relay A the fault is in Z2, for relay B it is inbackwards direction. Therefore relay B doesn’t send a signal to relay A, that would allow relay Ato trip instantaneously. Relay A trips with the delay time of Z2

There are different teleprotection schemes. Figure 2 describes a permissive underreach transfer trippingscheme (PUTT). Here a signal is only sent to the other end if a fault is detected in zone 1. It’s enough if onlyone relay detects a fault in its zone 1 to ensure that the fault is between side A and B. In this case the relayson both sides have to trip instantaneously. Zone 1 doesn’t cover the whole length of the line, this is why sucha scheme is classed as “underreaching”.

Figure 3: Principle of PUTT

In contrast a permissive overreach transfer tripping scheme (POTT) uses typically an extended zone (Z1B).This zone extends Z1 to cover a length that is longer than the line length (overreaching). Relay A and Bsend a release signal to the other end if a fault is within the respective extended zone. That means if bothrelays send a signal the fault is between them (see Figure 4). In this case the relays on both sides have totrip instantaneously.

Figure 4: Principle of POTT

The example of this application note uses a POTT scheme. For more information about Distance protectionsee [2].


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3 System under test

3.1 Application example - protected line and time grading

The following figure shows the line protected by distance teleprotection using a POTT scheme as describedin chapter 2.2.

communication connection

Line Data50 Hz

Solidly grounded110 kV600 A

32.5 kmR‘ = 0.193 Ohm/km

X‘ = 0.4 Ohm/kmRN/R = 0.6XN/X = 0.6

CT A600 A / 1 A

CT B600 A / 1 A

A B

Z1

Z1

Z1B

Z1B

Z2

Z2 70%

70%

VT B110 kV / 100V

VT A110 kV / 100 V

130% 130%

RelayB

Relay A

Figure 5: Example – Line protected by Distance Teleprotection using a POTT scheme (CT: Current Transformer; VT: VoltageTransformer)

Figure 5 shows that the extended zone (Z1B) reaches from 70% to 130% of the line length. A fault in thearea of 0% to 100% of the line length should lead to an instantaneous trip of relay A and B. It is assumedthat the relays of the example have an impedance tolerance of 5%.

Figure 6 illustrates the time grading of the distance protection. Both relays have two distance zones for theirforward and one zone for their reverse direction. The first zone has no delay which means the nominal triptime is 0 s. In the second zone the nominal trip time is 400 ms. The reverse zone has a delay time of 1.2 s.


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A B

Z1Z2

Z3

Z1

Z2

Z3

0 s

0.4 s

0.8 s

1.2 s

0 s

0.4 s

0.8 s

1.2 s

Z1B

Z1B

Figure 6: Example - Time Grading for Relay A and B (Blue: Relay A; Green: Relay B)

3.2 Settings of the system under test menu in RelaySimTest

The parameter of the protected line, the protection concept and the substations with their bays and relaysaccording to the example (see chapter 3.1 ) are in the System Under Test menu.

The red numbers in Figure 8 correspond to the numbers of Figure 5 and Figure 6 to show where thedifferent parameters are defined.

Comments:

> Number 1 → Protected line: The settings of this menu item use primary values.

> Number 3 → Bay A and B: This menu item contains the sub menu Instrument transformersthat includes the CT direction and the VT location settings.

Figure 7: Instrument transformers menu


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> Number 4 → Relay A and B: This menu item contains the test voltage and current limits. TheRelaySimTest template that corresponds to the application note was tested with a Siemens7SA63 relay system. The relay manual specifies that a current of 150 A for up to 10 s and a

continuous voltage of 230V do not cause damage to the relay [4]. The tests with the exampledata lead to currents that are smaller than 15 A and to voltages smaller 200V (Phase to Phase).The fault duration of one test point is about 2 s. Therefore a current limit of 15 A and a voltagelimit of 200V is suitable. Nevertheless it is important to do breaks between the tests to ensurethat the relays are not stressed too much.

Figure 8: System Under Test Menu


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4 Test cases

Figure 9 shows the Test cases menu. It contains the tests with their corresponding grid topology (1), testscenarios (2) and test steps (3). The next three chapter describe these menus referring to the test templateof the application note.

Figure 9: Test cases Menu

4.1 Application example – grid topology

The line protected by distance teleprotection is part of the grid that is shown in Figure 10.

Figure 10: Grid Topology


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4.2 Suitable test cases

This chapter describes the test of the corresponding RelaySimTest template.

To keep the template simple, it uses only the following Fault types:

> L1-N

> L2-L3

> L1-L2-L3

All test cases with faults include these fault types. Depending on the relays under test, on the relay’sparameter and on the grid where the protection system is used, it can be necessary to add more fault types.

The Initial state of a fault is inactive to get transients in the beginning. To get particularly high currents thefault inception angle is set to 0°.

Figure 11: Example for a fault with Initial state "Inactive"

The nominal trip time of the protection is between 0 and 1.2 s, therefore the simulation time after a fault orswitching event is at least 2 s. Hence the protection system has enough time to show its reaction on theevent.

Sometimes the distance protection relays use the voltage of their voltage memory, if the voltage during afault is too small to use it. Therefore it is necessary to fill this memory before the fault occurs. How long thistakes depends on the relay type. A Siemens 7SA63 relay system was used to test the template. Such arelay for example needs about 2 seconds to fill its voltage memory. Hence a prefault duration of 2 s is used.

Some of the test cases use a certain fault resistance RF to find out if the protection system can handle it. In

all test cases where the influence of RF is not considered RF is set to 0 .

The following chapters describe the different test cases of the template in detail. In all test cases the tripcommand of relay A and the trip command of relay B is observed. Chapter 4.3 describes how to measureand to assess the trip times.


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Test case 1 – double infeed, fault on line

This test case should show that a fault on the protected line leads to an instantaneous trip of theteleprotection system. The fault is placed on different fault locations.

> Fault locations: 0%, 50%, 100% of the protected line.

Figure 12: Test case 1

→ The fault is on the protected line, hence the relays have to detect it in zone 1 (Z1) or in theextended zone Z1B. In both cases they have to send a signal immediately to the other site whichreleases the extended zone of the remote relay. If a relay detects a fault in Z1, it has to tripinstantaneously. If it detects a fault in Z1B it has to trip instantaneously when it receives therelease signal from the other end.

Test case 2 and 3 – double infeed, line fault at 0 and 100%, RF and load current

These test cases should show that a fault on the protected line leads to an instantaneous trip of theteleprotection system even under unfavorable conditions.

> A fault resistance of 3 is used. It influences the fault loop impedance measured by the relays.(Number [2] of the bibliography shows how to estimate a fault resistance). Figure 13 illustratessuch an effect, if there would be only a single infeed at the relays site and no infeed at theremote line end. Furthermore the influence of a load current is neglected.


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X

R

RF

ZL

ZM

Figure 13: Influence of a fault resistance (ZL: Line impedance; RF: Fault impedance; ZM: Measured Loop Impedance)

> The influence of the fault resistance increases, if there is a load current and if there is an infeedat the remote end. Depending on the power direction the measured reactance increases ordecreases.

X

R

ZLZM

ZF

Figure 14: Influence of a fault resistance with an infeed at the remote end and a load current (ZL: Line impedance; ZF: Impedance dueto the fault resistance; ZM: Measured loop impedance)

> To realize the load current the phase angle of infeed 2 is varied, while the phase angle of infeed1 stays at 0°. For the tests phase angles of -30°, 0° and +30° are used for infeed 2. +-30° leadsin the grid of the example to a load current of about 510 A, this current is assumed as maximumload current. 0° leads to a no load condition.

> For test case 2 the fault location is at the beginning of the line (0%) and for test case 3 at theend of the line (100%). Especially these two locations can cause trouble, because they are atthe borders of the teleprotected area.


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→ Even if there are unfavorable conditions the fault is inside the area that is protected by theteleprotection system, therefore the relays have to behave in the same way they have to behavein test case 1.

Test case 4 and 5 – single infeed, fault on line (weak infeed logic test)

These test cases should show that faults on the teleprotected line lead to an instantaneous relay trip even ifthe remote relay does not detect the fault.

The reason why the remote end does not pick up could be a weak infeed. Figure 15 illustrates a weak infeedat site B. The relay on site A detects the fault in Z1B and sends a signal to relay B. On site B the fault currentis insufficient to cause a trigger of relay B. Hence relay B would not send a release signal and relay A wouldtrip with zone 2. Relay B on the other hand would not trip at all.

If a logic for weak infeed signals is used and relay B receives a signal while it has not detected the fault, thislogic checks whether the voltage is below a specific value. If this is the case, Relay B trips and sends anecho to relay A to release its extended zone.

With test cases 4 and 5 this logic is tested.

Figure 15: Weak infeed at site B

> The fault is placed at different fault locations: 0%, 50% and 100% of the line

> In test case 4 only Infeed 1 is modeled.


→ There is no infeed at the site of relay B, therefore it will not detected the fault. Nevertheless thefaults on the line have to lead to an instantaneous trip command of relay A and B due to theweak infeed logic.

> In test case 5 only infeed 2 is modeled.

→ There is no infeed at the site of relay A, therefore it will not detected the fault. Nevertheless thefaults on the line have to lead to an instantaneous trip command of relay A and B due to theweak infeed logic.


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Test case 6 and 7 – single infeed, fault on busbar

A fault on the busbar is out of the teleprotected area. These test cases should show that in such a case Z1Bis not released and that the trip times of the relays fit to the time grading of their distance protection.

> In test case 6 only infeed 1 is modeled

> The fault is placed on busbar B


→ The fault is out of the teleprotected area. Relay A has to trip with Z2. Relay B has to trip with itsreverse tripping zone (Z3).

> In test case 7 only infeed 2 is modeled

> The fault is placed on busbar A

→ The fault is out of the teleprotected area. Relay B has to trip with Z2. Relay A has to trip with itsreverse tripping zone (Z3).

Test case 8 and 9 – double infeed, fault on busbar, RF and load current

This test cases are similar to test case 6 and 7 but with unfavorable conditions. As shown in chapter 4.2.2 afault resistance as well as a load current and a remote infeed can cause trouble for the distanceteleprotection. These test cases should show that the relays can deal with this influences if a fault occurs onthe busbar.

> A fault resistance of 3 Ohm is used.

> The phase angle of infeed 2 is varied: -30°, 0°, +30° are used as phase angle of infeed 2, whilethe phase angle of infeed 1 stays at 0°.

> For test case 8 the fault is placed at busbar A

→ The fault is out of the teleprotected area. Relay B has to trip with Z2. Relay A has to trip with itsreverse tripping zone (Z3).


> For test case 9 the fault is placed at busbar B


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→ The fault is out of the teleprotected area. Relay A has to trip with Z2. Relay B has to trip with itsreverse tripping zone (Z3).

Test case 10: time grading without teleprotection

For this test case the teleprotection function has to be disabled. After the test it is very important toenable the teleprotection function again.

This test case should show that the relays use the distance time grading if the teleprotection is disabled.

> The zone borders between Z1 and Z2 are at 30% of the line for relay B and at 70% of the line forrelay A

> The zone tolerance is assumed to be 5%

> The fault is located around the zone borders but not inside the tolerance band

> Fault locations: 24%, 36%, 64%, 76%

Figure 19: Test Case 10

→ According to the time grading of the distance protection the relays have to show the following trip times:

Fault Location 24% 36% 64% 76%

Trip Time Relay A 0 s 0 s 0 s 400 ms

Trip Time Relay B 400 ms 0 s 0 s 0 s

4.3 Measurement and assessment

The Define Measurements menu of the Test steps tab (see Figure 9 number 3) defines the start and stopevent for the trip time measurements.

> The “start measuring event” is the beginning of a fault.

> The trip command is observed. The moment when the trip signal becomes active is the “stopmeasuring event”.

> The trip time is measured for relay A and B.


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Figure 20: Measurement

The Set Assessment Condition menu (next to the Define Measurements menu) defines the assessmentof the test steps. For all test cases (except test case 10) where the fault’s location is on the protected line the“Automatically obtain min/max time grading set in System under Test” option is active to use the timeassessment of the menu Protection concept (see Figure 8 number 2). For all the other test cases the minand max trip time values are entered manually. To do so the option “Custom min/max values” can be used(see Figure 21).

Figure 21: Automatically obtain min/max


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5 Test sets configuration

5.1 Test setup

Due to the distribution of the protection system an end to end test of a distance teleprotection system withtwo ends requires two CMCs. RelaySimTest offers the possibility to control both CMCs with one mainapplication via Internet. For this reason two computers with Internet access are necessary – one at the localand one at the remote end. The local PC runs the RelaySimTest main application, the remote PC just aproxy application which takes care of network connection issues and announces the test device to thecontrolling software application at the other end. This proxy application is the OMICRON Test Set Remote Agent . How to configure RelaySimTest and the Test Set Remote Agent for such an application is describedin the next chapter. Figure 22 illustrates the end to end test setup.

To perform a test the main application of RelaySimTest on the local PC calculates a fault scenario based on

the simulation of the power system network. It calculates the voltages and currents not only for its own endbut also for the remote end. The results are used for the end to end test where the main application controls

the local and the remote CMC.

To perform an end to end test for a distance teleprotection system synchronized injection of test voltagesand currents is necessary. The synchronization ensures that both test sets – the local and the remote one –start the test at the same time. This is very important since any inaccuracy can result in an unwanted testimpedance and thus in an unexpected relay behavior. For this reason RelaySimTest supports the use ofCMGPS 588 an antenna-integrated GPS controlled time reference to synchronize the starting point of aCMC test process. Each end needs its own CMGPS 588 (see Figure 22). It delivers a time signal using PTP(Precision Time Protocol). For more information about PTP see [3].

Figure 22: Scheme of an end to end test


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5.2 The Test sets configurations in RelaySimTest and the Test Set Remote Agent

This chapter assumes that the test set up according to chapter 5.1 is already done:

> The local PC is running RelaySimTest , the remote PC the Test Set Remote Agent.

> Both have Internet access.

> The wiring between the CMCs and the relays is already done.

> The local and the remote CMC are already switched on and synchronized via CMGPS 588.

> If the connections between the CMCs and the PCs are done by Ethernet, it has to be ensuredthat both CMCs are associated to the local PC.

The Test sets configurations menu (local PC) defines the CMCs and their configuration used for the tests. At first the test template includes two general CMCs as shown in Figure 23. The label on the left site of theCMC icon shows that the first CMC belongs to substation A and the second one to substation B.

Figure 23: Test sets configuration menu of RelaySimTest (local PC)

After a click on the “Choose test set” button on the right site of the CMC icon, a new window opens andoffers the CMC that is connected to the local PC. A click on the local CMC selects it.

Figure 24: Local CMC is selected

The Test Set Remote Agent on the remote PC (see Figure 25) has to open an Internet session beforeRelaySimTest can control the remote CMC. The upper part of the Test Set Remote Agent shows the remoteCMC. If the correct CMC is not already selected, it has to be chosen by using the “Change test set” button.


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A click on “Grant remote access” announces the remote CMC on an Internet server. After a short time theTest Set Remote Agent displays a session ID for the Internet session. The software offers also the possibilityto use a session password, but this is optional.

Figure 25: Test set remote agent (remote PC)

A click on “Connect to Remote Test Set” in the Test sets configurations menu of RelaySimTest (local PC)opens a window to enter the session ID from the remote end (see Figure 26).

Figure 26: Connect to remote test set (local PC)


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Afterwards RelaySimTest displays both CMCs – the local and the remote one. Figure 27 illustrates this. Thetest sets are ready for time synchronized injection due to the use of CMGPS 588. The green clock icon nextto the CMC icons indicate that.

Figure 27: Local and remote CMC connected to RelaySimTest

The Getting Started manual of RelaySimTest [1] describes how the wiring between the CMCs and the relays can beconfigured in the Test sets configurations menu. To perform the tests of this application note the following signals haveto be configured for each CMC:

> three test voltages

> three test currents

> the start, trip, send and receive signals of the relay


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6 Performing the test

Before a test is started it is strongly recommended to do a wiring check.

DANGER

Death or severe injury caused by high voltage or current.


NOTICE

Equipment damage or loss of data possible.


The execute buttons start the tests. There are different execute buttons - “Execute all” and “Executeselected”. What they mean depends on the menu where they are:

> If a test case is open a click on the “Execute selected” button executes only the selected teststep. A click on the “Execute all” button runs all test steps of the test case sequentially (seeFigure 28).

> In contrast to this in the Test Manager menu the “Execute selected” button runs all selected testcases, while “Execute all” runs all test cases (see Figure 29).

Especially after tests with high currents it is meaningful to interrupt the test sequence with the Stop button.

This ensures breaks between the tests to avoid too much stress for the relays.

Figure 28: “Execute selected” and “Execute all” button for a certain test case.


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Figure 29: “Execute selected” and “Execute all” button in the test manager menu.

List of literature

[1] Getting Started with RelaySimTest; OMICRON electronics GmbH; 2014

[2] “Numerical Distance Protection: Principles and Applications”; 4th edition; Gerhard Ziegler;PUBLICIS; 2011

[3] “Implementation and Transition Concepts for IEEE 1588 Precision Timing in IEC 61850Substation Environments”; B. Baumgartner, C. Riesch, M. Rudigier; OMICRON electronics

GmbH

[4] “SIPROTEC Distance Protection 7SA6 V4.70 Manual”, SIEMENS


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