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U.S. DEPARTMENT OF COMMERCE / National Bureau of Standards

A Measurement Assurance

Program for Electric Energy

QC

100

U5753

mo. 930

c.2

1976
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards' was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology

and facilitate their effective application for public benefit. To this end, the Bureau conducts

research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology,

the Institute for Computer Sciences and Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United

States of a complete and consistent system of physical measurement; coordinates that system

with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry,

and commerce. The Institute consists of the Office of Measurement Services, the Office of Radiation Measurement and the following Center and divisions:

Applied Mathematics — Electricity — Mechanics — Heat — Optical Physics — Center

for Radiation Research: Nuclear Sciences; Applied Radiation — Laboratory Astrophysics

" — Cryogenics ~ — Electromagnetics - — Time and Frequency -. THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to improved methods of measurement, standards, and data on the properties of well-characterized

materials needed by industry, commerce, educational institutions, and Government; provides

advisory and research services to other Government agencies; and develops, produces, and

distributes standard reference materials. The Institute consists of the Office of Standard

Reference Materials, the Office of Air and Water Measurement, and the following divisions:

Analytical Chemistry — Polymers — Metallurgy — Inorganic Materials — Reactor

Radiation — Physical Chemistry.

THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to promote

the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations leading to the development of technological standards (including mandatory safety standards), codes and methods of test; and provides technical advice and services to Government agencies upon request. The Insti- tute consists of the following divisions and Centers: Standards Application and Analysis — Electronic Technology — Center for Consumer

Product Technology: Product Systems Analysis; Product Engineering — Center for Building

Technology: Structures, Materials, and Life Safety; Building Environment: Technical Evaluation and Application — Center for Fire Research: Fire Science; Fire Safety Engineering.

THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and provides technical services designed to aid Government agencies in improving cost effec- tiveness in the conduct of their programs through the selection, acquisition, and effective

utilization of automatic data processing equipment; and serves as the principal focus within

the executive branch for the development of Federal standards for automatic data processing

equipment, techniques, and computer languages. The Institute consists of the following

divisions: Computer Services — Systems and Software — Computer Systems Engineering — Information Technology.

THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and

accessibility of scientific information generated within NBS and other agencies of the Federal Government; promotes the development of the National Standard Reference Data System and

a system of information analysis centers dealing with the broader aspects of the National Measurement System; provides appropriate services to ensure that the NBS staff has optimum

accessibility to the scientific information of the world. The Office consists of the following

organizational units: Office of Standard Reference Data — Office of Information Activities — Office of Technical

Publications — Library — Office of International Relations — Office of International Standards.

1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234.

- Located at Boulder, Colorado 80302.
!•< .: C O'-'' ^i^S

o

A Measurement Assurance

Program for Electric Energy

(\o ,

N. Michael Oldham

Institute for Basic Standards

National Bureau of Standards

Washington, D.C. 20234

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U.S. DEPARTMENT OF COMMERCE, Elliot L. Richardson, Secretary

Edward O. Vetter, Under Secretary

Dr. Betsy Ancker-Johnson, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

Issued September 1976
National Bureau of Standards Technical Note 930

Nat. Bur. Stand. (U.S.), Tech. Note 930, 23 pages (Sept. 1976) CODEN: NBTNAE

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1976

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 (Order by SD Catalog No. CI 3.46:930). Stock No. 003-003- Price 55 cents (Add 25 percent additional for other than U.S. mailing).
1. Introduction 1

2. New Calibration Service 2

3. Transport Standard Calibration 3

4. Measurement Assurance Program 4

5. Conclusions 6

6. Appendices

Appendix 1 Normalizing Terms 7

Appendix 2 Maintaining Process Control 8

Appendix 3 Test Instructions 11

Appendix 4 Report of Test 15

A MEASUREMENT ASSURANCE PROGRAM FOR ELECTRIC ENERGY

N. M. Oldham

A Measurement Assurance Program for Electric Energy is described which enables a meter laboratory to evaluate the accuracy of its calibration process relative to the legal unit of

energy maintained by the National Bureau of Standards. A laboratory participating in this program periodically determines

its process offset by testing an NBS transport standard as part

of its regular workload (using the same procedures used to test

its working standards). Subsequent monitoring and tests for

local control can improve the reliability and assure the adequacy of the participant's calibration process.

Key Words: Electric energy; electricity; electric power; measurement assurance; transport standard; watthour meter.

1. Introduction

The National Bureau of Standards is charged with the responsibility

of establishing and maintaining the national, legal unit of electric

energy at power frequencies. The unit is disseminated by NBS through

a watthour meter (Whm) calibration service and traditionally meter laboratories that use this service have sent their standard Whms to the

Bureau for calibration. Most of these laboratories maintain the unit

with one or more reference standard Whms which are used to calibrate

their working standards. These fall into two groups:

A. Standards that are used at the meter laboratory to test

industrial and residential type Whms before they are put

into service for billing purposes.

B. Standards that are used in the field to test Whms that are already in service.

The accurate calibration of these meters is therefore the principal function of most meter laboratories. Those who tie directly to the legal

units by shipping their reference standards to NBS run the risk of having

undetected systematic errors in their calibration process due to changes

in the standards during shipment or to peculiarities in the on-site test

conditions. To avoid this each laboratory is thus faced with devising a program to prove that the standards did not change during shipment and

that local test conditions introduce negligible uncertainties.

A new NBS calibration service greatly relieves the user of this re- sponsibility by providing a transport standard whose value and uncertainty at the time of use by the laboratory have been carefully determined.

By carrying out the transfer of the unit on-site with the procedures used

for its regular workload, statements can be made about the uncertainty
of its regular measurements. When this is accompanied by a program of

continuing surveillance of the workload by remeasuring a set of working

standards one has assurance of the validity of the uncertainty statements.

This effort to demonstrate that the measurement process is in a state of control has been given the name Measurement Assurance Program.

The laboratories who set up such a program can not only demonstrate the

adequacy of their measurement effort but also have the means for evaluating the effect of improvements to the process.

2. New Calibration Service

NBS now offers a new kind of calibration service which is designed

to reduce uncertainties and provide customers with improved measurement

reliability. It is based on similar services presently available in such areas as voltage and resistance which use NBS-owned transport standards

to disseminate the units. The transport standard (in this case a standard watthour meter) is shipped to a participating laboratory where it

is tested as an unknown using the same equipment and techniques normally

used to test the participant's working standards. Upon completion it is

returned to NBS for final calibration and data analysis. A test report

is issued (see Appendix 4) giving the difference between the unit maintained by the participant and the legal unit maintained at NBS, including a complete error analysis of the measurement.

Transport standards are commercial standard Whms carefully selected

to represent the best of each meter type. They are sent to the participant by commercial air freight with special ground transportation. Rugged, cushioned fiberglass containers are provided to reduce shipping

hazards and acceleration monitors on each meter detect unusually rough

handling. Barring mishaps in transit this new service can generally provide a more accurate means of tying to the national standards than the

traditional calibration service.

The registration of a transport standard may be affected by variations in test conditions such as voltage and temperature, and if the

test conditions at the participating laboratory differ from those at NBS,

a false offset may be observed. The participant is therefore asked to

record the average value of each parameter that may affect Whm registration during the test (see Instructions and Data Sheet - Appendix 3).

These values are used with previously determined parameter coefficients

for each transport standard to normalize the registrations to a single

set of test conditions - typically 120V, 5A, 300 or 600W, 60 Hz, 25°C and

sinusoidal waveform. For example, if the average temperature during a test is 23°C and the temperature coefficient of the transport standard is

0.010%/°C, the percentage registration will be normalized to 25°C by applying a 0.020% correction. The normalizing procedure compensates for

offsets and fluctuations in test conditions at both laboratories and will

generally further improve the accuracy of the calibration.

2
The accuracy of each parameter measurement is also important and can affect the uncertainty of the calibration procedure. For example, if the

voltage measurement is in error by 2 volts and the transport standard

voltage coefficient is 0.005%/V, when normalized the registration will be

in error by 0.010%. This would not pose a problem if all other working

standards calibrated by this precedure had the same voltage coefficient.

Whm coefficients, however, may vary in both magnitude and sign and care must be taken to minimize errors in each parameter measurement.

3. Transport Standard Calibration

NBS transport standards are compared to the average of the bank of

Whms (NBS primary standards) used to maintain the national unit of electric energy at 60 Hz. The formula used to compute the percentage registration of the transport standard r- T _ c is Nob

k n r

rNBS

= k n + P

NBS (3,1)

s s where

k = constant of the transport standard in energy per unit output,

n = number of unit outputs of the transport standard,

r = percentage registration of the NBS primary standards,

s k = constant of the NBS primary standards in energy per unit output,

s n = number of unit outputs of the NBS primary standards, and

s P„RC, = the normalizing term (see Appendix 1)

The first term of this equation describes the basic relationship between

the transport standard and the NBS primary standards. The second term

describes the effects of the parameters that may influence Whm registration.

The transport standard is calibrated at the participating

laboratory using the format outlined on the data sheet. It should be

tested as an unknown working standard and a value of precentage resistration r reported for each observation. When the results are processed at NBS, r . will be normalized to ^.t. at 120 volts, 5 amperes,

300 or 600 watts, 60 Hz, 25 °C and sinusoidal waveform by

^AB = rLAB

+ P

LAB (3 ' 2)

where PTAR is the normalizing term (see appendix 1).
The difference between the percentage registrations assigned at the

participating laboratory and at NBS is given by

AR " *LAB " *NBS

0.3)

where R^c = mean of r „ (computed before shipping to the customer f s laboratory) and r' (computed after return to NBS). The total uncertainty of AR using a 3 standard deviation limit is

U

AR " SU

NBS

+1V S

LAB

+S

NBS 0.*>

where

SU _ = systematic uncertainty of the NBS calibration process,

S = the standard deviation of the participant's calibration

process,

S,,,.^ = the standard deviation of the NBS calibration process, and

NBS

n = the number of independent observations made at each laboratory (an independent observation is loosely defined as a set of two or more readings separated by several hours from

any other set of readings)

4. Measurement Assurance Program

The NBS transport standard can periodically provide the participating laboratory with a means of evaluating its systematic errors. The

accuracy of local measurements, however, depends upon the performance of

the measurement process in between transport standard calibrations. This

note describes a Measurement Assurance Program which focuses on the properties of the measurements being made rather than the quality of the

standards used. It is the measurements (calibrations) made by the laboratory that its customers are concerned about - they all need assurance

that the uncertainty of these measurements is within the required limits.

Just as NBS has a Measurement Assurance Program to provide evidence of

the accuracy of its results so also does the participating laboratory

need its own program in support of its results.

If a stable meter were repeatedly measured over a long period of

time a sequence of non-identical results would be found. Evidence of

non-randomness might be present if the results were grouped by apparatus

used, ambient conditions or other factors. The random variability may

be of two or more levels; for example, duplicate measurements made in

the same hour may agree better than results from measurements made a day

or a week apart. One needs a procedure for determining these properties

some extra effort has to be devoted to just this purpose.
The participant's process has uncertainties caused by:

A. Systematic errors

1. Due to non-variable system errors which either escaped

detection or are known but left uncorrected (for example,

relay timing errors)

2. Due to the uncertainty of non-variable system errors for

which a correction is applied (for example, the uncertainty of a potential lead resistance measurement)

3. Due to the uncertainty of variable system errors for which

a correction is applied (for example, thermometer error which can result in uncertain temperature correction)

B. Random errors:

1. Due to random drifts in the entire calibration process

which cannot be accounted for.

2. Due to random process drifts which can be accounted for - type 3 systematic errors - but are left uncorrected (for

example, the uncorrected effects of random temperature

fluctuations)

Systematic errors can be determined by calibrating the NBS transport standard as a working standard. If the participant's corrections

are then adjusted to make AR = 0, the uncertainty due to the systematic

errors of the participant's process can be reduced to the uncertainty,

U.„, of the NBS transport standard calibration.

AR

Random errors of the process can be determined through local statistical analysis by the participant. This can be done by regularly

calibrating a group of typical working standards to determine the longterm process standard deviation. These repetitions should be done under

the same conditions as the regular workload. One wishes this sequence

of measurements to answer the question "What if the test meter had been

recalibrated at a later date - within what limits would such calibrations

fall?" It is therefore important that the sample group be representative

of the entire group of working standards calibrated by the participant

and that the measurements be taken far enough apart in time to be truly

independent. Ideally the long term process standard deviation S would be computed from measurements made on each of the working standards

at one or two week intervals.

Using information obtained from both the NBS transport standard and

local statistical analysis, the participant can calibrate a typical working standard to an uncertainty U
D

LAB " D

AR

+3 ^f <««

where

UA „ = the systematic uncertainty of the calibration process.

S T ._ = the long term standard deviation of the participant's

LAB

process

n = the number of independent observations made during the test.

The result is a program which can both transfer the legal unit to

the participating laboratory and provide a periodic monitor of the calibration process using accepted statistical techniques. It is designed

not only to provide measurement assurance but measurement efficiency as well. Once process control is achieved (tests for control are described

in Appendix 2), the calibration intervals may gradually be increased.

A meter laboratory wishing to participate in this Program for

Electric Energy should:

A. Calibrate a bank of typical working standards on a continuing

basis to determine a long-term standard deviation of the calibration process.

B. Calibrate an NBS transport standard.

C. Adjust its unit to make AR = 0.

D. Test for local process control at regular intervals.

E. Recalibrate an NBS transport standard (about one year after

the initial test).

5. Conclusions

A Measurement Assurance Program has been described which represents

a new philosphy in electricity metering. It focuses on the measurement

output of the meter laboratory rather than just the accuracy of its primary standards. A new calibration service which uses NBS transport

standards to determine the participant's measurement offset is now available. When this is combined with a regular program of surveillance of

the measurement effort by periodic measurements on the same group of

working standards, the laboratory can maintain continued assurance of

the adequacy of its measurements and the validity of its uncertainty

statements.

The procedures which enable one to characterize the measurement process also permit one to study its properties and the extent of improvement brought about by modifications in the process.
Appendix 1

Normalizing terms

These terms are used in eqs (3.1) and (3.2) to normalize NBS and

participating laboratory results to the nominal set of test conditions - 120 volts, 5 amperes, 300 or 600 watts, 60 hertz 25 °C, and sinusoidal

waveform.

P

NBS

=

[

(VNBS ~ V(CVNBS " C

Vt } + (INBS " V(C INBS " CIt

}

+ (WNBS * W

n

)(CWNBS " C

Wt>

+ (FNBS " F

n>

(C FNBS " C

Ft>

" (TNBS " Tn

)CTt

+ (HNBS " V(CHNBS " V]

where

A. V, I, W, F, T, H represent the parameters voltage, current,

power, frequency, temperature and harmonic distortion, res- pectively.

B. the subscripts NBS and n represent the average measured parameter value at NBS and the nominal value, respectively. (For

example, if the average measured voltage during a test at NBS

is 121 volts, VNRC? = 121 volts and the nominal voltage is

120 volts, V = 120 volts.) n

C. Coefficients are represented by C and the subscripts NBS and t refer to the NBS primary standards and the MAP transport standard, respectively. (For example, the voltage coefficient of

the MAP transport standards is represented as C„ ) . The temperature coefficient of the NBS primary standards C is

IN Bo

omitted because the standards are housed in a chamber whose

temperature fluctuations introduce a negligible error.

P

IAB " [°Vt<V„

" W + C

It

(In

" W +

°Wt

(Wn

" W

+ St (F

n

- W + C

Tt

(Tn

" T

LAB>

+

Sit <H

n

" W]

where the subscript LAB represents the average measured parameter value

at the participating laboratory.
Appendix 2

Maintaining Process Control

The validity of the uncertainty statement (4.1) depends on the process staying in a state of statistical control. Also it is assumed that

no dependence of the results on ambient conditions or other factors has

developed. Therefore the results on the bank of working standards should

be used to check these assumptions.

Standard deviation

After each set of about 4 to 8 results a standard deviation,

s , should be computed and the ratio

S LAB

- < / F(m -1, m-1, 0.99)

JLAB

compared with the critical value for /F given in the table where

m.. = number of values (independent observations) in sT

.

„

m = number of values (independent observations) in SLAB

If the critical value in the table is exceeded, then the process must

be regarded as out of control and the uncertainty statements are no longer valid. The process standard deviation should be redetermined.
G

•HBo

c

so

0)

0)

03

<D

<UU

too 0) T3

Percentiles of the F Distribution

F .99^m

l~ 1, m~^

m.-l = degrees of freedom for numerator

m-l\

1 2 3 4 5 6 7

30 7.6 5.4 4.5 4.0 3.7 3.5

J

3.3

\ 40 7.3 5.2 4.3 3.8 3.5 3.3 3.1

; 6o 7.1 5.0 4.1 3.7 3.3 3.1 3.0

120 6.9 4.8 4.0 3.5 3.2 3.0 2.8

00 6.6 4.6 3.8 3.3 3.0 2.8 2.6

Use of table:

For example, if S is computed from 41 independent observations

(m-1 = 40) it can be tested for consistency by computing sT based

LAB

upon four independent observations (m-1 =3). If s T A _/S < /4.3,

1 LAB LAB —

the test indicates that the process is in control.
Process average

The average registration for the bank of working standards can also

be used to monitor process performance if it is sufficiently stable (or

if its change with time is predictable). For the same grouping as with

the standard deviation check, compute the average, x and the ratio

m„

m, - xm

LAB

T m„ m

< 3

where

"x = the long term average registration,

x = the short term average registration m

°

If the ratio exceeds 3, checks should be made to determine whether

the working group has changed or whether it is the laboratory's reference standards which have changed.

Transport standard

The process offset (AR) will probably change from one transport

standard calibration to the next and while the participant's corrections

should initially be adjusted to make AR = 0, future adjustments to zero should be made only if

AR > IJ

AT* LAB

+ S

2 b

NBS

Further information on data analysis and statistical techniques is

available at NBS

10
Appendix 3

TEST INSTRUCTIONS

1. Before testing:

a. On transport standards equipped with accelerometers note if any

have been tripped (ball bearings rolling free in the plastic

housing) and record the g value and direction on the lid of the

meter. Reset the accelerometers using the attached tool, being

sure to match the spring to the set screw color code.

b. Level the meter using its level indicator.

c. Mount the enclosed thermometer on the meter in the designated

location and use it to record the average measured temperature

for each test run.

d. Isolate the test area from external magnetic influences.

Example: place the meter at least 20 cm (8 in ) from other

magnetic circuits and current carrying conductors.

e. Energize the current circuit with a continuous control - current

should be increased and decreased gradually, because current

switching transients can magnetize an induction watthour meter.

f. Energize at rated power at least 1 hour before the test. Internal

light sources where they exist must also be energized.

2. a. Unless other arrangements have been made, the transport standard

should be tested as an unknown working standard at 120 volts,

5 amperes - 1.0 power factor and 0.5 power factor current lagging.

b. To assure statistical independence, do not perform the test on a single day but rather over several days with 4 sets of readings

made for each power factor. Example: 1st day - take 2 consecutive

readings at each power factor in the morning and 2 at each in the

afternoon. 2nd day - repeat the procedure for a total of 8 observations per power factor. Use a separate data sheet for each power

factor

3. With each run, record Vatz, T<ur\<L, Pow&i VacXoft, Tn.an6p0fit Standard

Reading and ColAzcX&d PQAcentngz Rng<a>tficuticm (defined in the Code for

Electricity Metering as: "...The ratio of the actual registration of

the meter to the true value of the quantity measured in a given time,

expressed as a percentage". Example: if the meter registers 0.015%

fast, record as 100.015%). Report results to the nearest 0.001%.

11
Test Conditions

a. AueAage Mediated \)oJLvJLi>> These figures, to be recorded with each

run, are the average readings of the instruments used to measure

the different parameters and will partially compensate for random

variables such as voltage drift. Average readings are often

difficult to make without integrating instruments and unless such

equipment is available these figures will have to be operator

estimates. Example: if the voltmeter reading drifts uniformly

from 120 to 121 volts during a run, record 120.5 as the average

measured voltage. Comment on any measurement that was unusually

difficult to average - include numbers. The "remarks" column can

be used to record any unusual influences that vary from run to

run. Examples: electrical or mechanical shocks, distortion, etc.

b. M&aAuAHrmnt UncLeAtcU.n£i&> : These figures indicate the degree of

accuracy to which each parameter is measured and in general will

simply reflect the instrument accuracy. Example: in a voltage

measurement, if influences such as lead resistance are negligible,

the voltage measurement uncertainty figure will simply be the

voltmeter uncertainty.

c. Re<ivQ. HunvLctiXy: Record the average relative humidity during

the entire test period. Comment if there were large fluctuations

in this figure.

d. ?0t2.Wtiat Lzad R2A<U>tCLncZ'- Lead resistance in the potential circuit (between your standard and the meter under test) exceeding

0.05Q can cause significant power factor errors. Comment on com- pensation or corrections made for lead resistance.

e. HaAmonic VX^t0KiA.0n.> 3rd harmonic introduced into the current

circuit of an induction watthour meter will interact with 3rd

harmonic generated in the potential circuit of the meter to

produce an errorneous torque porportional to the harmonic magnitude and phase. The picture may be further complicated when

higher order harmonics are introducted into both the current and

potential circuits. Any information on harmonic content in both

waveforms will be helpful in establishina limits of uncertainty.

fSyAt&n StandcUid Vo.V-icuticm'> Most meter laboratories routinely

compare their working standards to their primary standards and

these measurements can be used to determine a process standard

deviation. If this figure is not provided the standard deviation of the actual MAP comparison (a less reliable figure) will

be used in the test report.

g. REMARKS: Use this space and the back of the data sheet to comment

on any pertinent measurement or estimate.

When information on a particular parameter is unavailable and a reasonable estimate cannot be made leave the space blank and comment in REMARKS,

12
5. When the test is completed place the data sheets in the shipping

container with the MAP transport standard and return them to NBS.

Shipping instructions

a. Ship air freight prepaid to Washington National, Dulles

International or Baltimore-Washington International Airport

on the route with the least number of transfers and stops.

b. Arrange to have the meter "hand carried" to the air freight

office if possible.

c. Where air freight is inconvenient choose the surface carrier

route with the least number of transfers and stops.

d. Mark the container:

HOLD AT AIRPORT (train station, etc.)

AND CALL - High Voltage Measurements Section

National Bureau of Standards

Gaithersburg , Maryland

(301) 921-3121

e. When the instrument is en route, telephone NBS (at the above

number) with pertinent transportation information including:

waybill number, carrier and flight number, destination and

estimated time of arrival.

13
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14
form NBS-259

(3/66) U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

WASHINGTON, D.C. 20234

REPORT OF TEST

OF

ELECTRIC ENERGY AT 60 Hz

USING

NBS TRANSPORT STANDARD NO.

Participating Laboratory

Measurements made by the participating laboratory on NBS Transport

Standard No. using its regular procedure for calibrating

standard watthour meters were as follows: (All results reported in

percent)

A. Offset Between Participating Laboratory and NBS

The percentage difference, AR, between L , obtained by the

participating laboratory and R^p* assigned by NBS was

Power Factor

1.0 pf 0.5 pf (lag)

AR ' KLAB " ^BS

U. (Uncertainty in AR)

211.06/

15
NBS TRANSPORT STANDARD NO.

Page 2

B. Process Parameters Used to Calculate AR and U

AR

1. Percentage registrations normalized to

120 volts, 5 amperes, 300 or 600 watts,

60 Hz, and 25 °C.

a. Measurements performed at NBS R^^e

b. Measurements performed at the participating laboratory R^

2. Systematic uncertainties in assigning the

units to the NBS primary standards SU „

3. The measurement process used by the participant to determine Rf.j, has:

a. long term (accepted) standard

deviations S_ ._ LAB

b. standard deviations for this

t6St S LAB

4. The measurement process used by NBS to

IBS

determine R>,r

r, has

a. long term (accepted) standard

deviations S. TT} _ Nob

b. standard deviations for this

teSt SNBS

Power Factor

1.0 0.5

C. Uncertainty

The uncertainty associated with the value of AR depends on the

systematic error in the value assigned by NBS and the extent to

which random error affects the measurements at both NBS and the

participating laboratory. The total uncertainty in AR with a 3

standard deviation limit for the effect of random error is

U*R " SU

NBS

+ 1 VH2

211.06/

+ M

16
NBS TRANSPORT STANDARD NO.

Page 3

Remarks

1. Results of F tests indicate:

a. Process in control Sjj^ used in

uncertainty statement

b. Process is either out of control or

SLAB is not 8 iven » S LAB used in

uncertainty statement

2. Results of test for offset indicate:

a. No adjustment for R should be made

b. AR is significant and corrections

should be adjusted to make AR =

3. Other:

1.0 pf 0.5 pf (lag)

n

For the Director

Institute for Basic Standards

OSKARS PETERSONS, Chief

High Voltage Measurements Section

Electricity Division

*U.S. GOVERNMENT PIIINTING OFFICE: 1976 210-801/411 1-3 17
NBS-114A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS TN-9302. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

A MEASUREMENT ASSURANCE PROGRAM FOR ELECTRIC ENERGY

5. Publication Date September 1976

6. Performing Organization Code

7. AUTHORS)

N. Michael Oldham

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

same as item 9

13. Type of Report & Period Covered Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary ol most significant information. If document includes a significant bibliography or literature survey, mention it here.) A Measurement Assurance Program for Electric Energy is described which enables a meter laboratory to evaluate the accuracy of its calibration process relative to the

legal units of energy maintained by the National Bureau of Standards. A laboratory

participating in this program periodically determines its process offset by testing an NBS transport standard as part of its regular workload (using the same procedures used

to test its working standards). Subsequent monitoring and tests for local control can improve the reliability and assure the adequacy of the participant's calibration

process.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Electric energy; electricity; electric power; measurement assurance; transport

standard; watthour meter.

18. AVAILABILITY Q£] Unlimited

H For Official Distribution. Do Not Release to NTIS

(5Q Order From Sup. of Doc, U.S. Government Printine Office Washington, D.C. 20402, SD Cat. No. CI 3. 46:93

_J Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCLASSIFIED

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

21. NO. OF PAGES

23

22. Price $0.55

USCOMM-DC 29042-P74

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step by step through the

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of color, influence of colors

upon other colors, and

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Send subscription orders and remittances for the pre- ceding bibliographic services to National Bureau of Standards, Cryogenic Data Center (275.02) Boulder,

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