Synchrophasor Measurement Standard – IEC/IEEE 60255-118-1

Synchrophasor MeasurementStandard – IEC/IEEE60255-118-1Presented byShane JinRTDS Technologies Inc.Texas A&M Relay ConferenceMarch 28, 2019

Working Groups JWG1 & H11Chair – Ken MartinGalina AntonovaGustavo BrunelloRen ChunmeiRatan DasWilliam DickersonDan DwyerJay GosaliaYi HuBrian KirbyHarold KirkhamVice Chair – Allen GoldsteinMarc LacroixShanShan LuoJay MurphyKrish NarendraDean OuelletteMahendra PatelShi BonianVeselin SkendzicEric UdrenZhiying Zhang

Outline Synchrophasor system overview Synchrophasor standards history Definitions & evaluation methods Requirement overview Annex review

Typical SynchrophasorMeasurement System Measurements at substations, real-time data sent to controlcenterData collected & aligned, sent on to applications or higher levelprocessingData StorageData StoragePMUPMULocal PDCCorporatePDCRegionalPDCPMUTransmission OwnerRegional Entity

First Synchrophasor StandardIEEE1344-1995 Measurement requirements Data transmission formats Time synchronization specifiedData sampling requirementsNo specification on resulting measurementUsed COMTRADE syntaxAdapted for single PMU & serial dataUnresolved issues & not widely implemented

Synchrophasor StandardC37.118-2005 Measurement requirements Data transmission formats Test method & error limits specifiedSteady-state phasor onlyImproved status and error indicationsIncludes single or multiple PMU dataAdaptable for network communicationWidely used & very few problems

Synchrophasor StandardsIEEE C37.118.x Existing C37.118-2005 split into two standards C37.118.1-2011 – Measurements only Add frequency & rate of change of frequency (ROCOF)Add Dynamic operation requirementsC37.118.2-2011 – Communications only For compatibility with IEC standardsMinimum changes, backward compatibleAdded a few needed improvementsC37.118.1a-2014 Amendment Modified requirements for achievability

IEC – IEEE Joint Project IEC/IEEE 60255-118-1 Jointly developed by combined IEC & IEEE WG IEC TC95 JWG1 IEEE PSRC H11 Started with IEEE C37.118.1 & C37.118.1a Considered suggested changes & expansions Added needed changes, updates, simplificationsCompleted in December 2018

IEC/IEEE 60255-118-1 – SummaryDefinitions for Synchrophasor, Frequency &ROCOF Measurement test & compliance requirements Steady-state includes accuracy and OOB rejection Dynamic tests include bandwidth, tracking, andresponse time Latency test for data output delay All tests include requirements for Phasor,Frequency & ROCOF

Synchrophasor Definition Extended Generalized case where all parameters change: Amplitude Xm(t)Phase θ(t)Additive signals D(t) The signal is defined: x(t) Xm(t) cos[θ(t)] D(t) Separate nominal signal from changes in phase:θ(t) 2πf0 t φ(t) The phasor value is: X (t) (Xm(t)/ 2)ej(φ(t)) Note that all phase variations including frequencydifferences are in the φ(t) term

Frequency & ROCOF DefinedFor the signal defined: x(t) Xm(t) cos[θ(t)] Frequency: f(t) 1/(2π) dθ(t)/dt ROCOF:ROCOF(t) df(t)/dt Same definitions at C37.118 series Frequency & ROCOF are instantaneous values

Measurement Compliance Evaluation of errorReference (theoretical) phasorvalueX Frequency error (FE) – differencebetween measured & referenceROCOF error (RFE) – differencebetween measured & reference2e jφ Xr jXiX(t 0) Xr (t 0) jXi (t 0)Measured (estimated) phasor valueTotal Vector Error – the RMSdifference)XmTVE (X r (t 0 ) X r )2 (X i (t 0 ) - X i )22Xr X i2𝐹𝐹𝐹𝐹(𝑛𝑛) 𝑓𝑓̂ 𝑛𝑛 𝑓𝑓𝑟𝑟𝑟𝑟𝑟𝑟 ��𝑑𝑓𝑓̂𝑅𝑅𝑅𝑅𝑅𝑅(𝑛𝑛) 𝑛𝑛 𝑛𝑛𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑

TVE EvaluationCompares the phasorsas vector quantities(total vector error) Both magnitude andphase angle evaluatedtogether Simplifies evaluation May mask individualphase angle andmagnitude problemsImaginary 𝑋𝑖 (𝑛𝑛)𝑋 𝑖 (𝑛𝑛)𝑋 𝑟𝑟 (𝑛𝑛)𝑋𝑟𝑟 (𝑛𝑛) Real

Additional Standard Features Performance classes Allow emphasizing certain uses P class for minimal delay, no filtering (think Protection) M class for more accurate reporting, may have delays(think Measurement) Either class can be used according to needsRequired data reporting rates extended Reporting 10 to 50 (50 Hz) and 10 to 60 (60 Hz)Reporting latency defined & added torequirements14

Key Steady-State Points Amplitude measurement Over frequency ranges Voltage 10-120% (80-120% P class), current 10-200 % Phase angle measurement checked at all anglesin frequency tests Interference rejection Harmonics Anti-alias for M-classAll tests laid out in series of tables (next slides)

Steady-State SynchrophasorMeasurementsReport rateindependentCorrected for report rateSeparate V &I tests

Steady-State Frequency & ROCOF

Dynamic Requirements Confirm measurement capability under dynamicsystem requirements Swings, switching, power imbalance Not intended for fault or catastrophic conditionsTests to confirm measurement compatibility Characterize instrument Emulate conditions of power system18

Modulation Tests Sinusoidal modulation of amplitude and phase angleof the fundamental signal Assures sufficient measurement bandwidth Emulates a system oscillationApplied as amplitude or phase individually Xa Xm [1 kxcos(ωt)] x cos [ω0t kacos(ωt-π)]Phasor, F, & ROCOF responses (points at t nT) X(nT) {Xm/ 2}[1 kxcos(ωnT)] {kacos(ωnT-π)} f(nT) ω0/2π - ka (ω/2π) sin (ωnT-π) ROCOF(nT) - ka (ω2/2π) cos (ωnT-π)19

Frequency Ramp Tests Constant ramp in frequency Determines measurement tracking systemXa Xm cos [w0t πRft2] where Rf is a constant ramp rateEmulates a system separation causing power-loadimbalanceRamp to frequency measurement limit M class: Fs/5 Hz up to 5 HzP class: 2 HzRamp rate 1 Hz /s20

Step Tests Step change of amplitude or phase Determines response time measurementXa Xm [1 kx f1(t)] x cos [ω0t ka f1(t)] where f1 is a unitstepEmulates a switch actionMeasurement values during the step are not evaluated(exclusion period)—only response time, overshoot, &delay10% amplitude, 10 phase Requires oversampling to get entire response 21

Step Illustration Response betweenleaving initial &achieving finalvalues Post-transition overshootSteady-state TVE limitstendApplied to phasor,Frequency, ROCOFDelay indicatescorrect timetagOvershoot limited22overshootPost step change levelResponse timeDelay timeSteady-state TVE limitststartInitial levelundershootT 0 (time of step)Illustration from IEEE C37.118.1

Modulation & Step ExamplesAmplitude &phasemodulation –pass bands aresimilar for both.Amplitude &phase steps –differences inresponse clearlyshown withdelayed sampling(slip-sampling)

Latency TestDelay from time ofmeasurement to datatransmission Includes algorithm,processing &communication delays Important forapplications sensitive todelays (eg. Controls) s ignal,Aphas 5Time (Sec )5.05phasor est.timetag5.15.15Processing,Etc.LatencyDatasent

Latency Test ExampleBaseline iswindowing delay 50 ms Additional 20 msdelay spikes everysecond due toprocessor orcommunicationdelays Delay - Ametek ata Points400050006000

Annex Information Annexes include reference material on phasors, algorithms,testing, time tagging, environmental testing and rotor anglemeasurement Annex E – sample value systems Analyzes the difference in measurement error sources Suggests adjustment of requirements for performanceAnnex G – normative requirements for extended accuracy A PMU may be certified for providing higher accuracy or extendedmeasurement rangesAnnex I – normative extended bandwidth determination Basic certification only determines that the PMU has a minimumbandwidth Provides procedures to determine the actual measurement bandwidth26

Differences between IEEE 37.118.1-2011and IEC/IEEE 60255-118-1 Certification only requires testing at one reporting rate Definitions changed but equivalent & compatibleTesting at different temperatures not requiredLatency test clarified and simplified Better meets user needsReduces testing cost and timeTemperature testing left to user requirements along with otherenvironmental requirementsNumerous clarifications includedNormative annexes for higher accuracy and bandwidthdetermination added27

Summary Covers full PMU performance certification Steady-state over full operating range Realistic dynamic operating conditions Compatible with the IEEE C37.118 International standard supported by both IEEEand IEC Published and available from both IEEE and IEC

27 Differences between IEEE 37.118.1-2011 and IEC/IEEE 60255-118-1 Certification only requires testing at one reporting rate Better meets user needs Reduces testing cost and time Definitions changed but equivalent & compatible Testing at different temperatures not required Latency test clarified and simplified Temperature testing left to user requirements along with other