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1660 IEEE TRANSACTIONS ON SMART GRID, VOL. 3, NO. 4, DECEMBER 2012

PMU Interoperability, Steady-State and DynamicPerformance Tests

Rui M. Moraes , Senior Member, IEEE , Yi Hu , Senior Member, IEEE , Gerard Stenbakken , Life Member, IEEE ,Ken Martin , Fellow, IEEE , Jose Eduardo R. Alves, Jr. , Senior Member, IEEE , Arun G. Phadke , Life Fellow, IEEE ,

Hector A. R. Volskis, and Virgilio Centeno , Senior Member, IEEE

Abstract— To ensure the performance of a synchronized phasormeasurement system (SPMS) to be deployed for the Brazilian in-terconnected national transmission network compliant to the spe-cific SPMS requirements, Operador Nacional do Sistema Elétrico(ONS) of Brazil has completed a phasor measurement unit (PMU)certification test as the first step of its PMU certification processfor the SPMS. PMUs from eight vendors were selected and testedin this project according to a comprehensive test program specif-ically developed for this certification project, which is based pri-marily on the IEEE C37.118-2005 standard as well as the specificrequirements of SPMS and its applications. This paper presents

and discusses the general background information, the developedtest program, the test unit selection and the testing processes, andthe overall test results of this project.

Index Terms— PMU, PMU dynamic performance, PMU testing,synchrophasor.

I. I NTRODUCTION

T HE SOLE independent power system operator in Brazil,Operador Nacional do Sistema Elétrico (ONS), is leading

a major effort to deploy a large scale synchronized phasor measurement system (SPMS) for the Brazilian interconnected

power system. SPMS will be used initially as a long term

system dynamics and event recording system for postmortemanalysis, model validation, and mitigation solution investiga-tion. Additional synchrophasor applications will be added tosupport ONS’s real-time system operator personnel decision.

The SPMS design includes phasor measurement units(PMU), substation phasor data concentrators (SPDC), centraldata concentrators (CDC) at ONS control centers, and thesupporting communication and networking infrastructure.

Manuscript received May27, 2011; revised September 30, 2011, February 07,2012, and May 16, 2012; accepted July04, 2012. Dateof publicationSeptember 07, 2012; date of current version December 28, 2012. Paper no. TSG-00190-2011.

R. M. Moraes is with Operador Nacional do Sistema Elétrico (Rio de Janeiro)and Universidade Federal Fluminense (Niterói), 200091-003 Rio de Janeiro,Brazil, and also with Universidade Federal Fluminense (Niterói), 24210-240São Domingos, Brazil..

Y. Hu is with Quanta Technology LLC, Raleigh, NC 27607 USA.G. Stenbakken was with the National Institute of Standards and Technology,

Gaithersburg, MD, USA and is now with GNSConsulting, Potomac,MD 20854USA.

K. Martin is with Electric Power Group (EPG), Pasadena, CA 91101 USA.J. E. R. Alves Jr. is with Centro de Pesquisa de Energia Elétrica, 21941-911

Rio de Janeiro) and also with Universidade Federal Fluminense (Niterói),24210-240 São Domingos, Brazil.

H. A. R. Volskis is with Operador Nacional do Sistema Elétrico, 200091-003Rio de Janeiro, Brazil.

A. Phadke and V. Centeno are with Virginia Tech, Blacksburg, VA 24061USA.

Digital Object Identifier 10.1109/TSG.2012.2208482

Utilities that own the substations where PMUs are to be in-stalled are responsible for the PMU procurement and installa-tion, as well as provisioning the communication and networkinglinks for sendingthe synchrophasor data to ONS control centers.It is expected that PMUs installed for SPMS will be supplied bymultiple vendors, as they will be procured through competitiveopen-bid process according to each utility’s substation equip-ment acquisition criteria [1]–[3].

To ensure that all PMUs to be acquired by different utilities

will meet the proper standard and SPMS requirements, ONS hasincluded a PMU certification process as an integral part of itsdeployment plan. To achieve this objective, ONS has developeda comprehensive PMU test methodology and the associated test

program, and carried out the first round of PMU certificationtests through a certification project on eight PMU products at anindependent test laboratory—the National Institute of Standardand Technology (NIST) of the United States [4].

In this paper, Section II describes the overall project with rele-vantdetails;Section III describes the test facility and test systemsetups used in the project; Section IV summarizes several issuesidentified during the preliminary tests of received test samples,and Section V provides a summary of the overall test resultsof eight selected PMUs in this project. Conclusions and recom-mendations are summarized and discussed in Section VI.

II. THE PMU CERTIFICATION PROJECT

The certification project was aimed at certifying off-the-shelf PMU products for immediate SPMS deployment. Onlysynchrophasor measurement related functionalities and the

performance were tested for each product in this project. Other tests, such as electrical, environmental, and electromagneticcompatibility tests, were not included in the test program of this

project. Multifunction devices with integrated PMU functionwere tested only when they can be configured and operated asa standalone PMU.

At the beginning of the project, vendors of PMU productswere invited to provide requested product information to ONSif they are interested in participating in this project. Received

product information was evaluated using a set of criteria to de-termine the readiness level of their products for participating inthis certification project.

Ten areas were evaluated for each product with the highestscore (5) assigned to conditions indicated below (after the“ ”): 1) meeting ONS specified requirements—fully meetall requirements; 2) type of device—standalone or can beconfigured and operated as a standalone device; 3) timing

source—has internal GPS receiver; 4) maturity—on the market

1949-3053/$31.00 © 2012 IEEE



MORAES et al.: PMU INTEROPERABILITY, STEADY-STATE AND DYNAMIC PERFORMANCE TESTS 1661

TABLE IPMU TEST PROGRAM

In this table, the column “CAT” denotes the type of tests, where “SI” is for “System and Interoperability”, “SS” is for “Steady-State” performance test,and “DP” is for “Dynamic Performance” test; the column “STD” is usedto indicate whether the test item is based on IEEE C37.118-2005 standardrequirement (“Y”) or not (“N”).

over 5 years; 5) product documentation—have all requireddocuments; 6) product type test—completed all tests withdocumentation; 7) PMU function test—have been tested withdocumentation showing IEEE C37.118-2005 compliance; 8)test sample information—have provided all request informa-tion; 9) ease of testing—very easy to setup and operate; and 10)test sample availability—available before the formal test starts.

Lower scores (from 1 to 4) were assigned for lesser conditions,and the total score is used as an indication of the readiness levelof a product for participating in this project.

Based on the assessment of the received information, ten ven-dors were invited to submit test samples (one PMU product for each vendor). Among them, eight test samples were submittedand completed the tests in this project. In this paper, these eighttested PMU products will be identified as PMU 1, PMU 2, ,PMU 8 respectively.

The project used a full test program including the test itemsas shown in Table I below.

As shown in Table I, the full PMU certification test program

consisted of three major parts: the system interoperability re-lated tests and verifications (SI), the steady-state performancetests (SS), and the dynamic performance tests (DP). The steady-state and dynamic performance tests were performed both at 12frames per second (fps) and 60 fps reporting rates.

Before proceeding to perform the tests listed in the full test program, certain preliminary tests (pre-test) were conducted oneach received test sample to ensure that it operates normally andis ready for the full test.

III. THE TEST FACILITY AND THE TEST SETUPS

All tests were performed at the NIST SynchroMetrology Lab-

oratory using itstwo test system setups. During all tests the tem- perature was maintained in the range .

Fig. 1. PMU steady-state performance characterization test setup.

A. PMU Steady-State Performance Calibration Test Setup

The steady-state PMU performance calibration test uses the NIST PMU steady-state performance calibration system setupas shown in Fig. 1 [5].

The calibration system is synchronized to UTC via a global

positioning system (GPS) clock. It provides UTC synchronizedthree-phase power signals to the PMU being calibrated (DUT).The PMUs output IEEE C37.118-2005 standard [6] formattedcontinuous data stream at rates from 10 to 60 messages per second.

The IEEE standard [6] requires the PMUs to have a totalvector error (TVE) of less than 1% under a number of test condi-tions described in the standard for level 1 compliance. The IEEEstandard does not specify a statistical basis for this requirement,

just that the maximum TVE must never exceed the limit. For ONS testing the test duration was selected to be 10 s. Thus, thelimit is compared to the largest of the 120 TVEs at 12 fps or

the largest of the 600 TVEs at 60 fps. These values are referredto as maximum TVEs in the following sections. TVE combinesthree error sources. Time errors (deviation of timestamped re-sults from true UTC time), phase errors, and magnitude errors.

The NIST calibration systems use a GPS clock with an uncer-tainty of 45 ns ofthe 1 pps from trueUTC. The phase error dueto uncompensated time deviation of sampling and calibration of

phase errors in the CTs and voltage attenuators is less than 300ns. Together these time errors contribute 0.01% to the TVE for a 60 Hz nominal frequency signal. The magnitude uncertaintyis less than 0.025%. With these estimated errors the NIST PMUsteady-state and dynamic performance calibration systems havean estimated uncertainty of less than 0.08% TVE three sigma.The variations of the TVEs for most DUTs during steady statetesting have a standard deviation of about 0.1%.

B. PMU Dynamic Performance Characterization Test Setup

The PMU dynamic performance characterization test setupuses the NIST PMU dynamic performance characterizationsystem as shown in Fig. 2 [5].

While similar to the NIST PMU steady-state calibrationsystem in its basic design, this system uses three voltage andthree transconductance amplifiers to provide the PMU testsignals in place of the commercial power simulators. Thewaveforms are generated in the synchronized generation andsampling unit (SGS) and output as voltages with a range of upto 10 V peak-to-peak. As the dynamic performance criteria




Fig. 2. PMU dynamic performance characterization test setup.

have not been developed and standardized at the time thiscertification test was performed, the system is used to charac-terize the performance of the PMU during various dynamicconditions.

IV. ISSUES E NCOUNTERED DURING PRE-TEST

Various issues were encountered and resolved during the pre-test stage, which allowed the test project to progress. These is-sues are summarized below:

Hardware related issue: PMU 1 experienced dif ficultiesto start up at the beginning of the pretest.

Incorrect Global Positioning System (GPS) clock

output : PMU 8’s own external GPS clock module had a1-ms shift in its output that could not be corrected.

GPS clock sensitivity: PMU 7’s own internal GPS clock module experienced dif ficulties locking onto a GPS signal

from the laboratory’s GPS antenna.Timing error : PMU 7 also exhibited a 23.5 ms timing

error during the pre-test after it was switched to use theIRIG-B timing signal.

Hardware calibration related problems: PMU 5 andPMU 6 were found to have large errors during the pretest.

These problems were corrected by software and hardware up-dates to the systems being tested.

V. PMU TEST R ESULTS

The summary test results are presented below in three major parts: the wide area measuring system interoperability relatedtests and verifications, the steady-state performance tests, andthe dynamic performance tests.

A. System and Interoperability Tests and Veri fications

1) TCP/IP, UDP/IP and Multicast Support: The ONS PMUspecification for SPMS stated that “ PMU shall support both

UDP/IP and TCP/IP protocols. The real-time data stream shall

be encapsulated in UDP/IP packets, and support both unicast

and multicast addressing. Message mapping requirements

are listed in section I.2 of Annex I of IEEE C37.118-2005

Standard .” The information provided by vendors and the testresults show that different methods have been implementedin the tested products for streaming real-time PMU data andexchanging other messaging frames (command, configuration,

TABLE IITCP/IP, UDP/IP, AND MULTICAST SUPPORT

Due to lack of documentation and equipment limitations, this could not be verified.

header) using IP communications. In all cases the device sup- plying the data is the server and the device receiving data is theclient. Each method has advantages and disadvantages whichare described as follows:

TCP-only method : This method uses one direct TCPconnection for transferring commands, data, header, andconfiguration frames between two connected devices.

UDP-only method : This method uses UDP for com-munication in both directions for PMU commands, data,header, and configuration.

Mixed TCP-UDP method : This method uses TCP for commands, header, and configuration communications,and UDP for sending data.

PMU initiated streaming data output (UDP auto): Thismethod generally means a PMU unit will send out dataautomatically without a start command and will not stop.

The data could be sent to a unicast , multicast , or broadcast IP address.

The information provided by vendors and the test resultshaveshown that vendors’ support of these methods in the tested unitsare not universal. Table II summarizes the supported communi-cation methods of the tested units.

The results show that there is only one product among thetested units that fully meets SPMS requirement, and none of them support all methods that would give users the flexibility tochoose any one of these methods to meet their specific systemrequirements. Users thus should always verify if a product sup-

ports the method required for their systems.

2) PMU Introduced Delays: PMU introduced delay is de-fined as the time difference between tagged time (measurementtime) and the time when the data leaves PMU. The PMU intro-duced delay includes the sample processing time, the phasor es-timation window length, the PMU computation time, output fil-tering, the time to transfer data to the communication output, theoutput clocking rate, and the way data is packed into the output

packets of the underlying communication protocols. Generallyspeaking, except for data packing caused delays, other delaysare very short as the test indicated, but may vary, particularlyfor multifunction devices.

An additional delay occurs if a PMU does not send out thedata frames each time one is available, but instead packing sev-eral data frames into one data packet, such as IP packet. Thecurrent IEEE standard [6] does not have requirements on this




TABLE IIIMESSAGE FRAME CHECK

type of PMU introduced delays, so the issue is not a standardcompliance issue but an application issue.

Depending upon the needs of actual applications, the abovePMU introduced delays in the tested units may or may not havereal impact on a specific application. Such delays may not beimportant for data archiving, but could become unacceptable

for a visual display and result in total delay exceeding the re-quirement for a high-speed control function. For some protec-tion and control applications, where point-to-point delay must

be less than 100–200 ms, such PMU introduced delay could bea major issue.

3) Message Frames Check: Message frames were checkedfor two reporting rates, 12 fps and 60 fps using steady-state

balanced three phase voltage and current inputs. The followingmessage frames were checked for IEEE standard [6] compli-ance: Configuration (CFG-1 and CFG-2), Data, and Header.The following commands were sent to the DUT to check itsresponses during these tests: 1) turn off transmission of data

frames; 2) turn on transmission of data frames; 3) send HDR frame;4) send CFG-1frame; and 5) send CFG-2 frame. Table IIIshow the message frames check results.

PMU 5 did not implement the Header message. Thus it failedthe Header frame test and it failed the command tests, sinceit did not send a Header frame when commanded to do so. Itresponded properly to the other commands.

4) Time Quality Tagging: Time quality (TQ) information isrequired by the IEEE standard [6]. The standard has specifiedrequirements for the use of time quality bits in the transmitted

phasor frames. This TQ byte includes 4 bits that indicate thequality of PMU time as estimated by the GPS receiver or based

on the PMU oscillator accuracy if the primary time source isunavailable.The test results of submitted units indicate that the implemen-

tations of the time quality codes are not universal. Vendor’s ap- proach for these TQ bits varied from not providing any estima-tion to implementing every TQ state as specified in the standard.

Table IV shows the time quality indication found in data mes-sages of tested PMUs.

The Max Clock Drift Rate is the drift rate of the internalclocks when the connection to GPS information is removed.

5) PMU Sync Indication: A PMU needs an external con-nection for UTC synchronization. The two approaches used byPMUs today are to build a GPS receiver into the PMU or inputtime from an external clock using IRIG-B or another time code(such as DCF77). The PMU also needs to know if the time

TABLE IVTIME QUALITY TAGGING

The number 00h means 00 in hexadecimal numbering. “Multi step” meansthe PMU indicated several levels of time quality uncertainty, “None” meansthat the PMU did not implement any time quality indications, “2-steps”means that the PMU changed only between two time quality levels of indication, and “None/2-steps” means that the PMU gave no change in timequality indication when the antenna was removed but gave two levels of timequality indication when the IRIG-B signal was removed.

TABLE VPMU U NLOCK AND SYNC I NDICATIONS

bi—built-in GPS receiver—disconnect IRIG-B connection test notapplicable. “OK” indicates that the function was implemented in accordancewith the standard IEEE C37.118-2005, “00/11 b” (or “00/10b”) indicatesthat the two Unlock time bits jumped from 00b to 11b indicating a changefrom synchronized to unsynchronized for more than 1000 s (or from 00 bto 10b indicating a change from synchronized to unsynchronized for morethan 100 s).

source is locked to GPS or not and the quality of the time signal.A built-in GPS receiver can communicate to the PMU whether it is synced to the UTC (locked to GPS) or not. The IRIG-Btime code defined in IRIG standard 200-04 does not specify timequality codes. The IEEE C37.118-2005 standard recommendedspecial control codes extension in the IRIG-B signal to com-

municate Time Quality and other time information to PMUsthat resolves this issue. However, a PMU without a built-inclock needs to use a clock that implements time quality controlcodes extension for IRIG-B signal and be able to interpret them.Table V shows how the PMUs supplied the PMU sync and theUnlock time indications in response to losing the GPS antennaconnection and the IRIG-B/DCF77 connection if used.

PMUs 5 and 7 failed to provide correct indications for lossof sync to UTC when the antenna to the external GPS clock was disconnected. PMU 5 did correctly indicate loss of sync toUTC within one minute, as required by the standard, when theIRIG-B input was disconnected, but PMU 7 had a delay of 290s before it indicated loss of sync to UTC when the IRIG-B inputwas disconnected. PMUs 1 and 2 have built-in GPS receiversso the removing IRIG-B connection test is not applicable.




TABLE VIR EPORTING R ATE R EQUIREMENT

TABLE VII[6] I NFLUENCE QUANTITIES AND ALLOWABLE ERROR LIMITS (LEVEL 1)

THD—Total harmonic distortion

6) Support All Reporting Rates for a 60 Hz System: ONS performance specification states that the PMU should supportall the reporting rates listed in the IEEE standard [6] for a 60Hz power system plus the additional rate of 60 fps as listed inTable VI.

The test checked the PMU performance at each reporting rate

by conducting a frequency variation test for each reporting rate.All tested PMUs responded to this test satisfactorily.

B. Steady-State Tests

The steady-state performance requirements for the PMU cer-tification test program can be summarized as: The PMU is ex-

pected to meet IEEE standard [6] level 1 performance require-

ment at all the reporting rates designated by the standard and

one additional reporting rate (60 fps) as shown in Table VII.Except for the unbalanced tests, all steady-state tests were

performed with a balanced three phase voltage and current inputs. The nominal magnitudes were 70 V and 5 A.

The voltage and current synchrophasors outputs from thePMUs were collected and their TVEs were calculated asthe difference from the calculated synchrophasors output of

NIST steady-state calibration system. The results below showthe TVE for either the voltage or current positive-sequence,whichever is larger. All steady-state performance tests wereconducted for two reporting rates: 12 fps and 60 fps.

1) Frequency Variation: The voltage and current input signalfrequency was varied from 54 Hz to 66 Hz in 0.1 Hz steps, whilethe magnitude was held at a reference value with harmonics andout-of-band interference both within the specified limits. Thetest at each frequency step runs for 10 s.

Table VIII shows the maximum TVE for the frequency vari-ation tests at 12 fps and 60 fps for the 55 Hz to 65 Hz range of the test.

TABLE VIIIFREQUENCY VARIATION

TABLE IXMAGNITUDE VARIATION

The results show that except for PMU 7, all other PMUs havea maximum TVE less than 1%.

2) Magnitude Variation: The voltageand current input signalmagnitude is varied from 10% to 120% in 5% steps in this test

program, while the frequency is held at a reference value with

harmonics and out-of-band interference both within the speci-fied limits. The test at each magnitude step runs for 10 s.

Table IX shows the maximum TVE for the magnitude varia-tion tests at 12 fps and 60 fps.

The results of magnitude variation test show that except for PMU 3 and 7 having maximum TVE greater than 1% at 12 fps,and PMU 3, 6 and 7 having maximum TVE greater than 1% at60 fps, all other PMUs have maximum TVE less than 1% at 12fps and 60 fps.

3) Phase Angle Variation: The voltage and current inputsignal frequency was fixed at an off-nominal value of 60.12 Hz,while the magnitude was held at a reference value with har-

monics and out-of-band interference both within the specifi

edlimits. The small off-nominal frequency causes the measured phase angle to constantly change without producing significantoff-nominal frequency effects. The test runs for 34 s allowing

phase angles to rotate completely through 360 several times.The TVE of voltage and current synchrophasors must be lessthan 1 % over t he f ull to range t o be i n compliancewith the IEEE standard [6] requirement. The results of phaseangle variation test (Table X) show that all PMUs have max-imum TVE less than 1% (phase error less than 0.57 ) at both 12fps and 60 fps.

4) Harmonic Distortion: The 2nd to 50th harmonics wereadded, a single harmonic at a time at a 10% level, to the voltageand current input signals. The magnitude was set at nominal,the frequency was 60 Hz (nominal) and the injected out-of-band




TABLE XPHASE A NGLE VARIATION

TABLE XIHARMONIC DISTORTION

interference within the specified limits. The test runs for 10 s for each individual harmonic injection.

Table XI shows that except for PMU 7 at 60 fps, all PMUshave maximum TVE less than 1% for both 12 fps and 60 fps.

5) Out-of-Band Signal Interference: The out-of-band test isdesigned to check that interfering signals that are beyond the

Nyquist limit of the phasor reporting rate are filtered so they donot corrupt the phasor estimates produced by the PMU. Thetests

performed were geared toward testing compliance with PMULevel 1 specification, of the IEEE standard [6], which requiresthat out-of-band signals with 10% magnitude should produceTVE of less than 1% in the estimated phasors.

There is a known issue for out-of-band performance compliance with IEEE standard [6]. At a 10 fps reporting rate, the Nyquist frequency is 5 Hz, so phasors cannot be reported at 55and 65 Hz (they will be aliased). In addition there is always

some fi

ltering stop band required between the measured bandand the out-of-band rejection, so cannot report accurately rightup to the Nyquist limit. Due to this issue, the minimum reportingrate tested in this certification test project was 12 fps.

The maximum TVE measured during this test for each PMUis shown in Table XII.

Test signals of 10% of the fundamental amplitude were addfor integer frequencies from 15 Hz to the lower Nyquist fre-quency (54 Hz for 12 fps and 30 Hz for 60 fps) and from theupper Nyquist frequency (66 Hz for 12 fps and 90 Hz for 60fps) to 130 Hz.

The results of the out-of-band interference test at 12 fps showa wide range of performance, with only one (PMU 1) closeto passing, and with two (PMUs 5 and 8) having TVE errorsgreater than the interference signal injected. The results of the

TABLE XIIOUT-OF-BAND SIGNAL I NTERFERENCE

Fig. 3. PMU out-of-band response.

out-of-band interference test at 60 fps show a wide range of per-formance, with four (PMU 1, 4, 5, and 6) passing the test, andfour others (PMU 2, 3, 7 and 8) failing the test.

Fig. 3 is a good example of the narrow band filtering that is

required to pass the out-of band test at 12 fps.Since the TVE at 54 Hz and 66 Hz exceed 1%, these results

show that this PMU did not quite pass this test.An argument could be made that out-of-band signals may not

be of great concern for many power system applications, be-cause often these signals are absent, or are very small in magni-tude. Thus, depending upon the application for which the mea-surements are to be used, the application may accept somewhatrelaxed level of compliance with this requirement.

6) Unbalanced Signal—Phase Unbalance: The test was con-ducted by shifting the phase angle of phase B from to

in 20 steps relative to the normal phasing. This

was done with both the voltage and current input signal whileholding the magnitudes fixed at the reference values, the fre-quency at the nominal 60 Hz, and harmonics and out-of-bandinterference signal within the specified limits. The test runs for 10 s for each phase angle shift.

The results of phase unbalance test (Table XIII) show that allPMUs have maximum TVE less than 1% at 12 fps and 60 fps.

7) Unbalanced Signal—Magnitude Unbalance: The test wasconducted with the phase B magnitude of both voltage and cur-rent input signals stepped from 0% to 120% of full scale in20% steps while keeping the other phases fixed at the refer-ence values. The frequency is held at the nominal 60 Hz andharmonics and out-of-band interference signals are within thespecified limits. The test runs for 10 s for each Phase B magni-tude value.




TABLE XIIIPHASE U NBALANCE

TABLE XIVMAGNITUDE U NBALANCE

The results of magnitude unbalance test (Table XIV) showthat all PMUs have maximum TVE less than 1% at 12 fps and60 fps.

C. Dynamic Performance Tests

The dynamic performance requirements for the PMU certifi-cation test program can be summarized as: The PMU is expected

to provide the desired dynamic performance in terms of band-

width, response time, and delay time during system dynamics,

considering the intended applications.All dynamic performance tests were performed with a bal-

anced three phase voltage and current inputs with nominal mag-nitudes of 70 V and 5 A. The synchrophasor voltage and cur-rent outputs were measured and recorded. The recorded data in-cluded the minimum, maximum, and mean of the error in mag-nitude, phase, and TVE of each phasor channel, as well as the

positive sequence synchrophasor values. TVE was calculated asthe difference between the PMU value and the NIST dynamiccalibration system calculated synchrophasor value. All dynamic

performance tests were conducted for two reporting rates: 12 fpsand 60 fps.

1) Magnitude and Phase Modulation Tests: Amplitude and phase modulation tests were run individually at modulation in-dices of 0.1 for both 12 fps and 60. TVE values for both modu-lations were determined with respect to the dynamic reference.The dynamic reference were the actual dynamic (time varying)values for magnitude and phase at each sample time. This de-termines the pass-band where the modulation is accurately rep-resented in the phasor output.

The phasor and frequency values output from the PMU under test were recorded at each modulation frequency. Similarly

TABLE XVPERFORMANCE LEVELS FOR MAGNITUDE & PHASE MODULATION TESTS

the test system derives the same values by measuring actualwaveforms at each modulation frequency. The two measure-ments were compared to derive the TVE for each modulationfrequency. Note that the test system analysis knows what thetest signal is so uses that information to derive the most accuratereference values.

This test is not part of the Standard. Two criteria were uti-lized to determine their effectiveness in showing the modulation

bandwidth of PMUs. The first criterion determins the maximum

frequency for which the maximum TVE remained less than 1%(the same criteria used in the steady-state tests). The second cri-terion, and the one used to qualify PMUs for ONS use, was themaximum frequency for which the average TVE over the test

period remain less than 3%.Tests ran for 10 s or two full cycles of the modulation,

whichever is longer.The performance levels of the magnitude and phase modula-

tion tests are as showed in Table XV.In the magnitude modulation tests, the phases of the inter-

fering signals are aligned and thus this test is better at showingthe positive sequence error response than the out-of-band inter-

ference test. The amplitude of the voltage and current test sig-nals was modulated with a sine wave for frequencies from 0.1Hz to 10 Hz in this test. The test was performed in steps of 0.1Hz up to 2 Hz, and in steps of 0.5 Hz from 2 Hz to 10 Hz. Theamplitude modulation index was set at 0.1.

In the phase modulation tests phase, the angle of the voltageand current test signals is modulated with a sine wave for fre-quencies from 0.1 Hz to 10 Hz in this test. The test was per-formed in steps of 0.1 Hz up to 2 Hz, and in steps of 0.5 Hzfrom 2 Hz to 10 Hz. The phase modulation index was set at 0.1.

The presence of the modulation in the data from the PMUsindicate how well they indicated the signal fluctuations for

low frequencies and how well they rejected the modulationsfor higher frequencies. As with the source, the presence of themodulation can be measured by the modulation index. For eachof the tested devices the modulation indexes of the PMU dataeither did not roll off for the amplitude or phase modulationindex, or the frequency modulation index did not roll off to alow values at and above the reporting rate Nyquist frequency.Presence of the modulation for higher frequencies was reflectedin the corresponding failures in the out-of-band interferencetests.

The Fig. 4 below shows sample results of the phase modula-tion test at 12 fps.

This plot shows that the pass band bandwidth was about 4Hz with respect to the maximum TVE of 1% referenced to thedynamic reference (solid curve) and about 6.5 Hz with respect




Fig. 4. PMU bandwidth for phase modulation test. Solid line shows maximumTVE versus modulation frequency. Dashed line shows mean TVE versus mod-ulation frequency.

TABLE XVIPMU PASS BAND

to the mean TVE of 3% (dashed curve). The bandwidth valuesdetermined from this test are shown in Table XVI.

Table XV gives the initial and final band pass criteria. Theresults in Table XVI indicated, the initial 1% pass band require-ment of 1.2 Hz at 12 fps was met by four PMUs and requirementof 6.0 Hz at 60 fps was met by two PMUs. The 3% pass bandrequirement (the one finally used by ONS) of 2.4 Hz at 12 fpswas met by seven PMUs and requirement of 12 Hz at 60 fps wasmet by three PMUs.

2) Magnitude and Phase Step Response: For the magni-tude step response test, the voltage and current test signals werestepped from nominal with a plus or minus 10% stepchange of their amplitude. For the phase step response test, thevoltage and current test signals were stepped from nominal with

a plus 10 or minus 10 step change applied to the testunit. Both tests started and ended with a steady signal to allowsettling at each value.

The step response time is the time from when the TVE ex-ceeds 1% until the time when the TVE drops below and remains

below 1%. The step delay time is determined by comparing themidpoints of the steps as shown by the PMU data with the timesof the steps. The steps occurred at 1 s and 3 s on the time axesof Fig. 5.

The performances of the magnitude and phase step changetests according to ONS requirements are as follows:

• For 12 fps response time less than 200 ms and delay timeless than 5 ms.

• For 60 fps response time less than 100 ms and delay timeless than 1 ms.

Fig. 5. Amplitude step test results for positive sequence V1 at 12 fps. Timeaxis is the PMU time tag values.

TABLE XVIIR ESPONSE TIME FOR MAGNITUDE AND PHASE STEP

In Fig. 5, the top row of plots shows a PMU magnitude re-sponse, positive step left and negative step right.

The middle row shows the phase change due to amplitudesteps. The lower row shows the TVE in % for both steps.

The magnitude step response plots in Fig. 5 show that thisdevice has a delay time less than 1 ms on both the rising andfalling amplitude steps. The plots in the middle row show thePMUs phase values were not significantly affected by the am-

plitude steps. The lower plots show the TVE exceeds 1% for 128 ms on both the rising and falling amplitude steps which isthe PMU response time. This test was run at 12 fps.

The results (Table XVII) show wide variations in the step test

response times. However the magnitude and the phase angleresponses within each unit are consistent. All PMUs had delaytimes within the desired performance values.

The requirements for response time are highly depend on theapplications. For visualization applications, the response timesshown above may not have much impact. For control applica-tions, a much faster response time is required. From the aboveresults, it appears that a response time below 100 ms at 60 fps isachievable for devices that also pass all other steady-state testsat 60 fps. For 12 fps, none of the tested PMUs had passed all thesteady-state performance tests, with only the PMU 1 comingvery close to passing. Based on the response time of PMU 1 at12 fps, a response time less than 200 ms appears to be achiev-able. Of course, this needs to be confirmed once PMUs are ableto successfully pass all steady-state performance tests at 12 fps.




Ken Martin (F’08) received the B.S. degree inelectrical engineering from Colorado State Univer-sity, Fort Collins, in 1970 and the M.A. degree inmathematics from the University of Washington,Seattle, in 1974.

He has over 30 years experience in the electricutility industry working at the Bonneville Power Administration (BPA) in communication, precisetiming, instrumentation, and testing. He initiated thefirst PMU tests with the original units introducedin 1987 and built the first phasor data concentrator.

He developed the phasor measurement system at BPA and supported similar developments at many utilities. He is a Consulting Engineer with the ElectricPower Group (EPG), Potomac, MD.

Mr. Martin chaired the development of the current synchrophasor, C37.118-2005 and currently chairs the IEEE groups developing the new C37.118 revi-sions and is also a lead forthe IECtaskteamdeveloping synchrophasorcommu-nication for IEC 61850. He is a Registered Professional Engineer. He continuesto develop synchrophasor technology at EPG, IEEE, and NASPI.

Jose Eduardo R. Alves Jr. (M’92–SM’06) receivedthe B.Sc., M.Sc., and D.Sc. degrees in electricalengineering from the Federal University of Rio de

Janeiro, Rio de Janeiro, Brazil, in 1986, 1991, and1999, respectively.

Since 1995 he has been with CEPEL, the BrazilianElectrical Energy Research Center, Rio de Janeiro,where he currently manages projects in metering. Heis also with Fluminense Federal University, Niterói,Brazil, as Adjunct Professor. His main research in-terests are in FACTS devices, power electronic con-

trollers, phasor measurement units, and metering.Dr. Alveshad been Chairmanof IEEE Rio deJaneiro Section, and is currently

a Member of CIGRÉ.

Arun G. Phadke (LF’03) received the M.S. degreein electrical engineering from Illinois Institute of

Technology, Chicago, in 1961 and the Ph.D. degreefrom University of Wisconsin, Madison, in 1964.

He is a University Distinguished Professor (Emer-itus) at Virginia Tech, Blacksburg. His primaryresearch area is the microcomputer based moni-toring, protection, and control of power systems. Heis a coauthor of two books on relaying: Computer

Relaying for Power Systems, and Power System Relaying , and is the editor of and contributor to the

book Handbook of Electrical Engineering Computations.

Dr. Phadke was awarded the IEEE Third Millennium Medal in 2000, namedthe OutstandingPower Engineering Educator by the IEEEin 1991, and receivedthe Power Engineering Educator Award of the EEI in 1986. He received theIEEE Herman Halperin Transmission and Distribution award in 2000. He wasthe Chairman of the Technical Committee of USNC CIGRE, and Editor-In-Chief of IEEE TRANSACTIONS ON POWER DELIVERY. He was elected to theU.S. National Academy of Engineering in 1993. He was awarded an HonoraryDoctorate by INP Grenoble, France, in 2006.

Héctor A. R. Volskis received the B.Sc. degree inelectrical engineering from the Fluminense FederalUniversity, Niterói, Brazil, in 1984. He receivedthree different M.Eng. degrees: in computer engi-neering from the Rio de Janeiro State University,Brazil, in 1987, in economic engineering from theRio de Janeiro Federal University, Brazil, in 1990,and in power system control engineering from theSanta Catarina Federal University, Florianópolis,Brazil, in 1994.

He is with ONS, the Brazilian Power System Op-erator, Rio de Janeiro, since 1999 as Specialist Engineer, where is responsibleto identify new technologies to assist real time decision making operation, in-cluding phasor measurements applications in real time operation. His main re-

search interests are power system tools, state estimation,and power system widearea measurements.

Virgilio Centeno (M’92–SM’06) received the M.S.and Ph.D. degrees in electrical engineering from Vir-ginia Polytechnic Institute and State University (Vir-ginia Tech), Blacksburg, in 1988 and 1995, respec-tively.

He worked as a Project Engineer at Macrodyne,Inc., Clifton Park, NY, in the development of phasor measurement units from 1991 to 1997. He joined thefaculty of Virginia Tech as a Visiting Professor in thefall of 1997 and became an Associate Professor in2007. His area of interest is wide area measurement

and its applications.

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