TUTORIAL 5 Modern Transient and Dynamic Testing

Modern Transient & Dynamic Testing

Uttam Mishra Ranvir Bariya

Doble Engineering Company

Outline • Introduction of Steady state, dynamic and Transient

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Testing Why Transient & Dynamic relay testing? What is the existing relay test practice? How the existing practice may be enhanced? What would be the new testing methodology and tools? Conclusions Q/A

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Test types

Steady state Testing (all protection )

Dynamic Testing (all protection )

Transient Testing (all protection )

End to end Testing (line protection ) Title

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Steady State Testing • It is defined as applying phasors to determine relay settings by slowly varying relay input up to pre determined value. • Steady state testing is usually used for pickup tests. The injected current/voltage/frequency is raised/lowered until the relay responds accordingly.

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Steady State Testing • The rate of change is slow enough so, it is time consuming test. • Steady state test signals are commonly used for individual relay calibration / testing.

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Dynamic Testing • Dynamic-state testing is defined as simultaneously applying the fundamental frequency component of voltage and current that represents power system states of pre-fault, fault and post-fault.

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Dynamic Testing • The dynamic state simulation signals are often helpful in testing protection systems that filter out all components of the signal except the fundamental frequency.

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Transient Testing • Transient testing is defined as simultaneously applying fundamental and non fundamental frequency components of voltage and current that represent power system conditions obtained from digital fault recorders (DFR) or electromagnetic transient programs (EMTP). • Analysis of questionable relay operation • Transient simulation signals reproduce all components of a test signal that are important to the performance of a protection system.

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Transient Testing • The current in Figure , for instance, is injected into an overcurrent relay to test the response of the relay to the high peak current that flows during the first cycles of energization.).

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Transient Testing • The response to this type of signal (of a relay used for protecting a capacitor bank) cannot be determined from steady state or dynamic state signals, and is normally also not discernable from the manufacturer’s application guide. • Testing by transient simulation is one way to gain insight into what might be a secure setting. • Testing of individual applications using transient test signals is often an important aid to developing reliable and fast protection applications and settings.

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End to End Testing

Comm Channel

Protection under test

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End to End Testing • Ultimate testing tool • Evaluates complete relay and associated equipment performance • Co-ordination between two end of relaying scheme – Current reversal – Evolving fault • Must for critical lines • Ensures proper operation of the complete relaying scheme

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What is the existing relay test practice? • Phasor testing procedure which does not represent power system condition • Sets a fixed voltage and ramps current from zero until the relay operates. Repeats such a test for several operating points. • The existing approaches in transient testing provide basic idea how the transient tests should be conducted. • The existing approaches are in most cases aimed at some specific situation when transient tests are required. • Majority of relay test engineers just continue to use what is “easy” and believe that “it is just not necessary!. It is a waste of time!” • Not very difficult but pre-planning work is needed than to use the steady state methods. Title

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Why Transient & Dynamic relay testing? • Provide complete protection scheme testing under realistic power system condition • Numerical relays respond to transients differently. They use signal processing techniques and numerical algorithms to calculate the fault. In each calculation step, samples of transient voltages and currents are processed • Some relays have over 2000 setting possibilities • Increases productivity, reduce testing time • Requires extensive configuration and setting procedure. • To implement conformance and compliance test • Cause of failure can be investigated • When the new relays need to be procured. User can assure weather a given relay is suitable for the specific power system application by testing a relay under realistic conditions Title


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Test Methodology Generate a set of test scenario through simulation programs Collect useful fault recording and of black out events Create standard steps for automated testing Automate the simulation to minimize test time Finally create a test library Implement comparative tests for a set of different relays with similar functions • Collect relay response events, analyze the results and summarize them in a test report with comparative results. • • • • • •

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Creating Test Library

Conformance test

Power System Model

Test Library

Compliance test

Fault Records

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Confirmance Test • The objective is to test the basic functionality of the relays, verify the operating characteristics, calibrate relay settings and implement periodic maintenance test. • The concern of this test is the statistical performance related to the relay operating characteristic and tripping time. To fulfill this test, a batch of test cases with a variety of disturbance conditions including faults and non-faults are generated through simulation.

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Fault Scenario ( sensitivity) • Verify whether relay has successful to detect internal and external fault • Switch on to fault detection • Verify ability to trip relay when fault occur during power swing • Verify auto reclose and auto reclose operation • Verify capability of relay to trip on internal fault during system frequency fluctuates in normal range

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SOTF Test

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Auto reclose scheme test

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Power Swing during fault

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No fault Scenario ( stability ) • • • • •

Verify the relay ability not to trip at stable power swing Verify the relay ability not to trip overload conditions Loss of potential Loss of load Load encroachment

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Power swing block

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Compliance Test • The objective of compliance application test is to verify whether a relay can operate correctly under peculiar circumstances in power system particularly during abnormal operating conditions. • The response and relay operating time performance under specific scenarios is checked Eg. Use of the recorded data to analyze causes of an unwanted relay operation in a pre and post-event analysis. • Those possible scenarios which may cause relay unintended operation will be recorded and saved into the test case library.

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Test scenarios for Compliance Tests Relay performance on 3 Phase power swing / out of step Cross country fault

Parallel line out of service

Fault in reverse direction Title

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Power Swing / out of step

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Cross Country fault • A fault can occur, for instance, between phases A and B but the phases belong to different lines on the same tower. The undesired operation of the relays at substation R can occur because they must rely on the local phase selection to determine the fault type and which phase or phases to trip.

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Parallel line out of service • Parallel line out of service can cause unwanted operation of distance relays. When overhead lines are connected in parallel or run in close proximity for either the whole or a part of their length, mutual coupling exists between the two circuits

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Fault Reversal condition

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Power System Model (PSM) • Power system model contains thousands of nodes • A reduced-size power flow case with a manageable number of dynamic system models is needed for real time testing. • Reduction of a full dynamic system model to a small dynamic model requires testing on the full power flow and dynamic model to determine which portions of the power system are electrically remote from the line being tested. • Doble has Power System model for real time testing • This model represents two machines equivalent with lumped impedance parameter for line and source value

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PSM Programs

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Using Power System Model • Power system model contain four power system configuration: – – – –

Single line Parallel line Single line with tap Parallel line with tap

• Obtain source impedance and line impedance at both ends of line • Enter impedances as positive , negative and zero sequence impedance. • Select fault location or drag and drop the fault location sign and run the test

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Equivalent PSM

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Equivalent PSM

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DFR’s of black out and critical faults • Generate test scenarios. Test cases (ATP, MAT or COMTRADE file) are generated through batch simulation program

• cases of interest are selected from digital fault recorder (DFR) files or blackout event files.

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Software Framework

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Doble Testing Software

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Transwin Software features • • • •

Transient fault record playback Dynamic conditions can be created Transient data can be recorded Application for end to end testing

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Using the new Protection suite 2.1

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Benefits of Protection Suite 2.1 • One relay assistant software for complete relay performance testing • Steps can be created for performance testing • Protection suite will be able to create one library for all tests • Same library can be used for testing all relays of similar functions. • Comparison of Settings. • Create and edit characteristics with a few simple steps. • Software User Interface enhancements. Title


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Conclusion Reduced time to test complete protection Faster diagnostic of questionable operations Confirm actual settings Relay PERFORMANCE evaluated to assure the BEST decision regarding application practices & relay performance under critical conditions • Utilities have used dynamic relay testing to find problems that were unexplained with previous test methods. • Incident reports can now be meaningfully investigated. • • • •

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TUTORIAL 5 Modern Transient and Dynamic Testing

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