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IEC 60255-181 Edition 1.0 2019-02 INTERNATIONAL STANDARD NORME INTERNATIONALE M

IEC 60255-181 Edition 1.0 2019-02 INTERNATIONAL STANDARD NORME INTERNATIONALE Measuring relays and protection equipment – Part 181: Functional requirements for frequency protection Relais de mesure et dispositifs de protection – Partie 181: Exigences fonctionnelles relatives aux protections de fréquence INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION ELECTROTECHNIQUE INTERNATIONALE ICS 29.120.70 ISBN 978-2-8322-6496-6 ® Registered trademark of the International Electrotechnical Commission Marque déposée de la Commission Electrotechnique Internationale ® Warning! Make sure that you obtained this publication from an authorized distributor. Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé. colour inside This is a preview - click here to buy the full publication – 2 – IEC 60255-181:2019 © IEC 2019 CONTENTS FOREWORD ........................................................................................................................... 6 1 Scope .............................................................................................................................. 8 2 Normative references ...................................................................................................... 9 3 Terms and definitions ...................................................................................................... 9 4 Specification of the function ........................................................................................... 13 4.1 General ................................................................................................................. 13 4.2 Input energizing quantities / energizing quantities ................................................. 13 4.3 Binary input signals ............................................................................................... 14 4.4 Functional logic ..................................................................................................... 14 4.4.1 Operating characteristics ............................................................................... 14 4.4.2 Reset characteristics ..................................................................................... 17 4.5 Additional influencing functions/conditions ............................................................ 18 4.5.1 General ......................................................................................................... 18 4.5.2 Specific characteristics for under/over frequency function .............................. 18 4.5.3 Specific characteristics for rate of change of frequency (ROCOF) function ......................................................................................................... 19 4.6 Binary output signals ............................................................................................ 19 4.6.1 General ......................................................................................................... 19 4.6.2 Start (pick-up) signal ..................................................................................... 19 4.6.3 Operate (trip) signal ....................................................................................... 19 4.6.4 Other binary output signals ............................................................................ 19 5 Performance specification ............................................................................................. 20 5.1 General ................................................................................................................. 20 5.2 Effective and operating ranges .............................................................................. 20 5.3 Accuracy related to the characteristic quantity ...................................................... 21 5.4 Start time for under/over frequency function .......................................................... 21 5.5 Start time for rate of change of frequency (ROCOF) function ................................ 21 5.6 Accuracy related to the operate time delay setting ................................................ 22 5.7 Disengaging time .................................................................................................. 22 5.8 Reset hysteresis and reset ratio ............................................................................ 22 5.9 Accuracy related to restraint/blocking elements .................................................... 23 5.10 Performance with harmonics ................................................................................. 23 5.11 Stability in case of sudden voltage change (phase shift and magnitude shift) ........ 23 5.12 Voltage input requirements ................................................................................... 23 6 Functional test methodology .......................................................................................... 24 6.1 General ................................................................................................................. 24 6.2 Determination of steady state errors related to the characteristic quantity ............. 26 6.2.1 Accuracy of the start value ............................................................................ 26 6.2.2 Reset hysteresis or reset ratio determination ................................................. 32 6.3 Determination of the start time .............................................................................. 41 6.3.1 General ......................................................................................................... 41 6.3.2 Under/over frequency .................................................................................... 41 6.3.3 Rate of change of frequency .......................................................................... 47 6.4 Determination of the accuracy of the operate time delay ....................................... 50 6.4.1 General ......................................................................................................... 50 6.4.2 Description of test method ............................................................................. 50 6.4.3 Reporting of the operate time delay accuracy ................................................ 52 This is a preview - click here to buy the full publication IEC 60255-181:2019 © IEC 2019 – 3 – 6.5 Determination of disengaging time ........................................................................ 53 6.5.1 General ......................................................................................................... 53 6.5.2 Under/over frequency .................................................................................... 53 6.5.3 Rate of change of frequency .......................................................................... 56 6.6 Performance with harmonics ................................................................................. 58 6.6.1 General ......................................................................................................... 58 6.6.2 Accuracy of the under/over frequency start value in the presence of harmonics ...................................................................................................... 58 6.6.3 Accuracy of the ROCOF start value in the presence of harmonics ................. 63 6.7 Stability in the case of sudden voltage change (phase shift and magnitude change) ................................................................................................................ 65 6.7.1 General ......................................................................................................... 65 6.7.2 Performance in case of voltage phase shift and magnitude change ............... 65 6.7.3 Performance in case of voltage magnitude drop and restoration .................... 68 7 Documentation requirements ......................................................................................... 70 7.1 Type test report .................................................................................................... 70 7.2 Other user documentation ..................................................................................... 71 Annex A (normative) Test signal equation with constant frequency variation (df/dt) .............. 72 Annex B (normative) Calculation of mean, median and mode ............................................... 73 B.1 Mean .................................................................................................................... 73 B.2 Median .................................................................................................................. 73 B.3 Mode .................................................................................................................... 73 B.4 Example................................................................................................................ 73 Annex C (informative) Example of frequency measurement and calculation ......................... 74 C.1 Definitions............................................................................................................. 74 C.2 Signal observation model ...................................................................................... 74 C.3 General requirements on frequency measurement ................................................ 76 C.3.1 General requirements on frequency measurement ......................................... 76 C.3.2 Periodic algorithm .......................................................................................... 76 C.3.3 Analysis algorithm ......................................................................................... 78 C.3.4 Error minimization algorithm .......................................................................... 79 C.3.5 Discrete Fourier transformation (DFT) ........................................................... 82 Annex D (informative) Performance with inter-harmonics ..................................................... 84 D.1 General ................................................................................................................. 84 D.2 Proposed test: accuracy of the under/over frequency start value ........................... 84 D.2.1 Description of the generated frequency ramp ................................................. 84 D.2.2 Protection function settings ............................................................................ 85 D.2.3 Test points and calculation of frequency accuracy in the presence of interharmonics .............................................................................................. 86 D.2.4 Reporting of frequency accuracy in the presence of inter-harmonics .............. 86 Annex E (informative) Management of sudden frequency change without discontinuity in voltage waveform .............................................................................................................. 87 Bibliography .......................................................................................................................... 90 Figure 1 – Operate time and operate time delay setting ........................................................ 11 Figure 2 – Simplified protection function block diagram ......................................................... 13 Figure 3 – Underfrequency independent time characteristic .................................................. 15 Figure 4 – Overfrequency independent time characteristic .................................................... 16 This is a preview - click here to buy the full publication – 4 – IEC 60255-181:2019 © IEC 2019 Figure 5 – ROCOF independent time characteristic (for negative or positive ROCOF) ........... 16 Figure 6 – Explanatory diagram for start, operate, disengage and reset ................................ 18 Figure 7 – Example of test method for overfrequency ........................................................... 26 Figure 8 – Example of test method for positive ROCOF function ........................................... 29 Figure 9 – Frequency ramps for assessing the reset hysteresis for overfrequency functions ............................................................................................................................... 33 Figure 10 – Frequency ramps for assessing the reset hysteresis for underfrequency functions ............................................................................................................................... 33 Figure 11 – Test method for measurement of reset value for ROCOF functions: example for positive ROCOF function ................................................................................... 37 Figure 12 – Start time measurement of overfrequency with sudden frequency change .......... 42 Figure 13 – Start time measurement of overfrequency with constant slope frequency ramp ..................................................................................................................................... 43 Figure 14 – Example of start time reporting for under/over frequency protection function ................................................................................................................................. 47 Figure 15 – Start time measurement of positive ROCOF function .......................................... 48 Figure 16 – Histogram for the start time test results for ROCOF............................................ 50 Figure 17 – Operate time delay measurement of overfrequency and positive ROCOF ........... 51 Figure 18 – Disengaging time measurement of overfrequency with sudden frequency change .................................................................................................................................. 54 Figure 19 – Disengaging time measurement of overfrequency with constant slope frequency ramp ..................................................................................................................... 54 Figure 20 – Disengaging time measurement of ROCOF ........................................................ 56 Figure 21 – Histogram for the disengaging time test results for ROCOF ................................ 58 Figure 22 – Example of an increasing pseudo-continuous ramp for overfrequency functions ............................................................................................................................... 59 Figure 23 – Voltage signal with superimposed harmonics ..................................................... 61 Figure 24 – Representation of the input energizing quantity (voltage, RMS) injection sequence .............................................................................................................................. 67 Figure 25 – Representation of the input energizing quantity (voltage, RMS) injection sequence with the power system frequency values ............................................................... 69 Figure C.1 – Zero-crossing algorithm .................................................................................... 77 Figure C.2 – Level-crossing algorithm ................................................................................... 77 Figure D.1 – Example of an increasing pseudo-continuous ramp for overfrequency function ................................................................................................................................. 84 Figure E.1 – Example of voltage waveform without discontinuity at to = 0,02 s...................... 88 Figure E.2 – Example of voltage waveform with discontinuity at to = 0,02 s .......................... 89 Table 1 – Frequency protection designation ............................................................................ 8 Table 2 – Example of effective and operating ranges for over/under frequency protection ............................................................................................................................. 20 Table 3 – Example of effective and operating ranges for ROCOF protection ......................... 20 Table 4 – Test points for under/over frequency function ........................................................ 28 Table 5 – Reporting of the frequency accuracy ..................................................................... 28 Table 6 – Reporting of the frequency accuracy (alternative solution) ..................................... 29 Table 7 – Test points for ROCOF function ............................................................................. 31 Table 8 – Reporting of ROCOF accuracy .............................................................................. 32 This is a preview - click here to buy the full publication IEC 60255-181:2019 © IEC 2019 – 5 – Table 9 – Test points of reset hysteresis for under/over frequency function .......................... 35 Table 10 – Reporting of the reset hysteresis for over/under frequency functions ................... 36 Table 11 – Test points of reset value for ROCOF function ..................................................... 40 Table 12 – Reporting of the reset value for ROCOF function ................................................. 40 Table 13 – Test points of start time for overfrequency function ............................................. 44 Table 14 – Test points of start time for underfrequency function ........................................... 45 Table 15 – Reporting of start time for under/over frequency functions ................................... 46 Table 16 – Test points of start time for ROCOF function ....................................................... 49 Table 17 – Reporting of typical start time for ROCOF function .............................................. 50 Table 18 – Test points to measure operate time delay .......................................................... 52 Table 19 – Test points for accuracy of the operate time delay ............................................... 52 Table 20 – Reporting of operate time delay accuracy for under/over frequency functions ............................................................................................................................... 53 Table 21 – Test points of disengaging time for overfrequency function .................................. 55 Table 22 – Test points of disengaging time for underfrequency function................................ 55 Table 23 – Reporting of disengaging time for over/under frequency functions ....................... 56 Table 24 – Test points of disengaging time for ROCOF function ........................................... uploads/Management/info-iec60255-181-ed1-0-b.pdf