P-E-01—Procedures for calibrating and certifying electricity meter calibration consoles pursuant to EL-ENG-12-01—Requirements for the certification of measuring apparatus —electricity meter calibration consoles

7.0 Procedures for the assessment of metrological requirements
(EL-ENG-12-01, s. 7.0) (part 4 of 4)

7.8 Console calibration (EL-ENG-12-01, 7.8) (part 2 of 2)

7.8.7 Remarks (continued)

  1. Errors determined for a configuration at one MUT positions only shall be applicable to each MUT position.
  2. For all of the tests set out above, the test burden determined pursuant to sections 7.3.4.5, 7.3.4.6 and 7.3.4.7 shall be connected in each MUT position, with the exception of the position with the standard (and transformer combination); this position shall have the applicable voltage burden connected in parallel with the standard. In the case where the test load exceeds the voltage or current rating of the meters used to burden the MUT position, higher rated meters shall be used to burden the MUT positions.
  3. Burdens are not required to be installed for the calibration of the console (i.e. section 7.8) if the errors determined pursuant to the applicable subsections of section 7.3 of EL-ENG-12-01 for determining burden effects differ by 0.05 percent or less.
  4. In the case of test burdens that are required and are rated lower than the voltage that is being calibrated, suitable burdens with voltage ratings equal to the calibration voltage shall be used as required.
  5. Calibration consoles equipped with more than one reference meter shall be calibrated with all reference meters that will be in circuit simultaneously while the console is used for the verification of meters.
  6. Calibration consoles that will be used with more than one reference meter either in or out of circuit shall be calibrated for all combinations of reference meters that will be in circuit simultaneously while the console is being used for verifying meters.
  7. Where a console is used with variable combinations of reference meters in or out of circuit, the console shall be calibrated at the test load and test burden pursuant to section 7.2 of EL-ENG-12-01 for each combination of reference meter in or out of circuit. The console shall be deemed acceptable for use for each combination of reference meter in or out of circuit that results in errors that are within 0.05% of each other.
  8. The calibration console certified must clearly indicate on the certificate which reference meters are in circuit for the errors established on the certificate. The certificate must also indicate all certified combinations of reference meters that will be used with the console.

7.9 Measurement uncertainty (EL-ENG-12-01, s. 7.9)

7.9.1 Purpose

The purpose of section 7.9 of EL-ENG-12-01 is to establish uncertainties for certified console errors by accounting for uncertainty contributors identified 7.9.3.1 below.

7.9.2 Guidelines

The certified errors of a console shall be provided with uncertainty figures obtained by following one or more of the procedures below. The uncertainty contributors are determined by assessments made under section 7 of EL-ENG-12-01.

7.9.3 Combined console uncertainty

7.9.3.1 Influences

The combined uncertainty of the calibration console errors includes the following sources of uncertainty:

  1. Burden Effects – The maximum spread determined in section 7.3.4 of the procedure above.
  2. Variation from Position to Position - The maximum spread determined in section 7.4 of the procedure above.
  3. Regulation – The maximum one-minute deviation from target determined from section 7.6 of the procedure above.
  4. Current Switching Effects – The maximum spread per 7.7 of the procedure above.
  5. Reference Standard – Value from the certificate of calibration (default value of 0.005 if not available).
  6. Repeatability – As determined per 7.9.3.11 below.
7.9.3.2 Reduction equation for console uncertainty

The console error uncertainties are established by use of data secured during the assessments of requirements of the relevant sections of EL-ENG-12-01. Relevant data is to be used in the following equation:

Uc(con) = √[((Ube ÷ 3)^2 + (Uptp ÷ 3)^2 + (Ucse ÷ 3)^2 + (Ucm ÷ 3)^2 + (Urs ÷ 2)^2 + (Urep ÷ 2)^2)]

where:

7.9.3.3 General procedure

The uncertainty is established by use of the uncertainty value for each applicable influence factor related to a test point or a group of test points. The number of calculations required is dependant on the extent of certification of a console. A console with less than 100 certified errors requires this calculation to be performed for each console error provided. Other consoles need this calculation performed for each table of the certificate (by measurement unit and console configuration combination). The uncertainty due to regulation is applicable only to demand test points. The needed data for calculation of the uncertainty can be extracted from the worksheets that are completed during the certification process.

7.9.3.4 Uncertainty due to burden effects

The burden effects section evaluates the uncertainty due to various burdens under several console configuration and use situations. The process identified in sections 7.3.4.5 to 7.3.4.7 provides such values to be used as the Ube in the reduction equation as applicable.

7.9.3.5 Uncertainty due to position-to-position errors

Section 7.4 of EL-ENG-12-01 establishes position-to-position error spreads for multi-position consoles. That value represents the Uptp value for this influence in the reduction equation. A single position console will not have an uncertainty contribution due to position-to-position errors.

7.9.3.6 Uncertainty due to current switching effects

Current switching effects uncertainty contribution applies only to automatic and semi-automatic consoles. The maximum spread between the errors observed during the assessment of current switching errors in section 7.7 of EL-ENG-12-01 provides the values to be used as Ucse in the reduction equation for automatic and semi-automatic console, as applicable.

7.9.3.7 Uncertainty due to regulation

Consoles used to verify demand meters will have an uncertainty in the certified demand errors due to the console regulation. The highest deviation from target value obtained during the evaluations per section 7.6 of EL-ENG-12-01 is to be used as the Ucm factor in the reduction equation, when applicable.

7.9.3.8 Reference standard uncertainty

The reference standard used to calibrate the console as per EL-ENG-12-01 is a source for uncertainty in console calibration. The uncertainty of the reference standard to be used as the Urs factor can be found on the calibration certificate for the standard.

7.9.3.9 Uncertainty due to repeatability
7.9.3.9.1 General guidelines

The Urep is established on the basis of five repetitions of a test point. Urep is determined by the procedures provided below:

  1. For consoles that are certified at less than 100 test points, the uncertainty due to repeatability is established for each test point included in the console certificate.
  2. For consoles that are certified at more than 100 test points, the uncertainty due to repeatability is established for test points and determined by the procedures below.
7.9.3.9.2 Test point selection
  1. For each combination of console configuration and measurement unit, the following test points shall be assessed 5 times, as applicable:
    1. The smallest test load used in 7.8 for this combination. The tests shall be performed at unity power factor for Watt/Wh and at 0.5 power factor for VA/VAh and VAR/VARh.
    2. The maximum test load used in 7.8 for this combination. The tests shall be performed at 0.5 power factor for Watt/Wh and VA/VAh, and at 0.866 power factor for VAR/VARh.
    3. The lowest and highest current test points for the I-squared hour function.
    4. The lowest and highest voltage test point for the V-squared hour function.
7.9.3.9.3 Test positions
  1. On multi-position consoles, the tests shall be performed five times at MUT positions as follows:
    1. For console configuration as per 7.2.1.3 (a) and (b) of EL-ENG-12-01, the smallest and the largest test loads shall be assessed in the odd and even MUT positions respectively.
    2. For console configurations as per 7.2.1.3 (c) or (d) of EL-ENG-12-01, the tests shall be conducted at any one MUT position.
7.9.3.9.4 Example
  1. The repeatability uncertainty figures established are to be reported separately for energy and demand applications. An example of the number of repeatability tests required for a 10-position console with all the possible measuring units to be certified is as follows:

    Repeatability tests
    Configuration Measurement unit Number of test points
    Total 72 points
    Parallel Wh 2
    VAh rms 2
    VAh avg 2
    Varh 2
    I2h 2
    V2h 2
    1:1 Wh 10
    Varh 10
    VAh 10
    Without 1:1 Wh 10
    Varh 10
    VAh(rms) 10
  2. These 72 test points shall be repeated at least 5 times.

7.9.3.9.5 Effective uncertainty due to repeatability
  1. For consoles that have fewer than 100 test points, the certified error shall be the average of five repetitions and the uncertainty value to be used as the Urep in the reduction equation for each specific test point shall be determined by the following formula based on five repetitions:

    s = √((1 ÷ (n − 1) × ((x1 − (1 ÷ n(x1 + x2 + … + xn)))^2 + ((x2 − (1 ÷ n(x1 + x2 + … + xn)))^2 + … + ((xn − (1 ÷ n(x1 + x2 + … + xn)))^2))) ÷ n)]

    Where:

    • s = standard uncertainty
    • n = number of tests
    • x = test point error
    • = average error
  2. For consoles that have greater than 100 test points, the uncertainty value shall be determined for each test point repeated pursuant to 7.9.3.9.1(1) above using the following formula based on five repetitions:

    s = √[((1 ÷ (n − 1) × ((x1 − (1 ÷ n(x1 + x2 + … + xn)))^2 + ((x2 − (1 ÷ n(x1 + x2 + … + xn)))^2 + … + ((xn − (1 ÷ n(x1 + x2 + … + xn)))^2)))]

    Where:

    • s = standard uncertainty
    • n = number of tests
    • x = test point error
    • = average error
7.9.3.10 Official uncertainty figures
  1. The values determined by the use of the reduction equation above (7.9.3.2) for all test points, or all applicable test points used for combinations of console configurations, measurement units, test types (energy or demand) and influence factors are the standard uncertainty figures. A coverage factor of k = 2.0 shall be applied for reporting these figures on the console's certificate of calibration.
  2. The uncertainty figures shall be recorded on the console's certificate as the highest values for each of the following configurations, as applicable:
    1. Console using parallel transformer connections.
    2. Console using 1:1 isolation transformers.
    3. Console using multiple transformers without 1:1 isolation transformers.

    When using the certificate, the highest value of uncertainty obtained may be used for all certified console errors provided on a certificate or in a table.

  3. The uncertainty figures determined in 7.9.3.9.1(2) shall be established and reported separately for energy and demand applications.

General example

  1. In this example, information was extracted from a typical calibration console worksheet used to establish an uncertainty for the console calibration. The console is a multi-position board used to verify many different types of meters, including single-phase and polyphase meters. As a result, there is calibration data for single-phase meters (1:1 transformers are in circuit) as well as data for all other meter types. In this particular example, the 1:1 transformers are used for energy meter testing only. There may be situations where the demand meter testing may also require the use of 1:1 transformers. In this case, the uncertainty due to regulation will need to be included as well.
  2. There are two sets of calibration errors established for this console. The uncertainty contributors are identified first.

Uncertainty due to burden effects

  1. In this example, the test burden is established for the two conditions of use. One is the test burden with the 1:1 transformers in circuit and the other is the test burden for all other applications. Data is established for each 1:1 transformer position under section 7.8 of EL-ENG-12-01 for console calibration. This means that there will be an uncertainty figure associated with each of the 1:1 positions. As an example, in this case, position 3 has a spread of errors between high capacitive burden and high inductive burden of 0.02%.
  2. In the case of calibration when 1:1 transformers are not in circuit, the uncertainty is determined to be 0.01%.
  3. The above values will be used as the Ube factor in the reduction equation for each of the configurations.

Uncertainty due to position-to-position errors

The uncertainty contribution from position-to-position errors only applies when 1:1 transformers are not in circuit. In our example, the difference between the greatest and smallest errors represents the uncertainty due to position-to-position errors. In this example, the maximum spread is 0.01%. This value shall be used as the Uptp factor in the reduction equation for the "other meters" only.

Uncertainty due to current switching effects

The uncertainty contribution due to current switching effects is established from the spread of errors observed over five runs. In our example, table 7.7 indicates a spread of 0.03% for configurations using 1:1 transformers and 0.01% for "other meters". These values will be used as the Ucse factor in the reduction equations for each of the configurations.

Uncertainty due to the reference standard used for console calibration

The reference standard used to certify the console will have an uncertainty found on the certificate of calibration for the standard. In this example, a value of 0.005% is used as the Urs factor.

Uncertainty due to repeatability

The uncertainty contribution due to five repeated runs is to be calculated using the formula:

s = √[((1 ÷ (n − 1) × ((x1 − (1 ÷ n(x1 + x2 + … + xn)))^2 + ((x2 − (1 ÷ n(x1 + x2 + … + xn)))^2 + … + ((xn − (1 ÷ n(x1 + x2 + … + xn)))^2)))]

s = 0.004% for this example

Calculations

  1. Use the formula below with the applicable contributors.

    When 1:1 transformers are not in circuit:

    Uc(con) = √[((Ube ÷ 3)^2 + (Uptp ÷ 3)^2 + (Ucse ÷ 3)^2 + (Urs ÷ 2)^2 + (Urep ÷ 2)^2)]

    where:

    • Uc(con) = Combined standard uncertainty of console
    • Ube = 0.01% (uncertainty due to burden)
    • Uptp = 0.01% (uncertainty due to position to position errors)
    • Ucse = 0.01% (uncertainty due to current switching effects)
    • Urs = 0.005% (uncertainty due to reference standard used to certify the console)
    • Urep = 0.004% (uncertainty due to repeatability)

    Uc(con) = √[((0.001 ÷ 3)^2 + (0.01 ÷ 3)^2 + (0.01 ÷ 3)^2 + (0.005 ÷ 2)^2 + (0.004 ÷ 2)^2)]

    = ±0.007%

  2. This uncertainty represents the standard console uncertainty for the errors established in the case of no isolation current transformers (1:1).
  3. A coverage factor of k=2 provides an expanded uncertainty value of ±0.013%.
  4. This value should be stated on the certificate of errors.
  5. When 1:1 transformers are in circuit, an uncertainty figure shall be established for each position of the console. In each case, the uncertainty shall be stated with the respective console position errors established under section 7.8.
  6. As an example of position 3 in the data sheets, the relevant contributors are:

    Uc(con) = √[((Ube ÷ 3)^2 + (Uptp ÷ 3)^2 + (Ucse ÷ 3)^2 + (Urs ÷ 2)^2 + (Urep ÷ 2)^2)]

    where:

    • Uc(con) = Standard uncertainty of console
    • Ube = 0.02% (uncertainty due to burden)
    • Uptp = N/A (uncertainty due to position to position errors, because each position is being calibrated).
    • Ucse = 0.03% (uncertainty due to current switching effects)
    • Urs = 0.005% (uncertainty due to reference standard used to certify the console)
    • Urep = 0.004% (uncertainty due to repeatability)

    Uc(con) = √[((0.02 ÷ 3)^2 + (0.00 ÷ 3)^2 + (0.03 ÷ 3)^2 + (0.005 ÷ 2)^2 + (0.004 ÷ 2)^2)]

    = ±0.012%

  7. The expanded uncertainty of ±0.024% with k=2 can be stated on the certificate of errors for position 3 with 1:1 transformers.

7.10 Pulse counters and generators

7.10.1 Purpose

The purpose of section 7.10 of EL-ENG-12-01 is intended to ensure that all calibration consoles which utilize internal or external pulse counters and generators for verification testing meet the tolerances pursuant to section 7.10 of EL-ENG-12-01.

7.10.2 Guidelines

The pulse counters used with calibration consoles are verified by supplying 1000 pulses into them and checking that 1000 pulses were counted by the counter. Pulse generators used with calibration consoles are verified by counting 1000 pulses output by the generators. The pulse generators are also verified at the maximum frequency or input pulse rate required to verify pulse recorder inputs. If a console utilizes both pulse counters and pulse generators, the pulse counters can be verified first, and if accepted, they can be used to verify the pulse generators.

7.10.3 Procedure

  1. Connect the pulse generator(s) to supply the same pulse to all pulse counters to be certified with the console.
  2. If one generator cannot control all of the counters to be certified at one time, connect it to the maximum number of counters the generator can control.
  3. If another generator is available, connect it to the remaining counters to be certified.
  4. If there is only one pulse generator available, the test must be repeated for the remaining pulse counters to be certified.
  5. Supply a minimum of 1000 pulses into the pulse counter(s) under test at a rate equal to the maximum pulse rate the console is used to verify.
  6. If all the counter positions/channels cannot be tested at one time, repeat for the remaining pulse counters.
  7. The expected number of pulses counted by the pulse counters must be within 1 pulse. Any pulse counter that does not meet this tolerance will not be certified to be used for testing pulse meters.
  8. Enter the position and number of pulse counters to be certified on the worksheet.
  9. Connect the appropriate pulse counter(s) to each position that operates as a pulse generator.
  10. Set the generators to supply a minimum of 1000 pulses into the pulse counters at the maximum rate for which the generator is to be certified. This rate is not to be less than the maximum pulse rate of the meters with pulse outputs the console is used to verify.
  11. The number of generated pulses at each position/channel to be certified must be within 1 pulse. Any pulse generator that does not meet this tolerance will not be certified for testing pulse recorders or any other device that operates from a generated pulse and is used for revenue billing.
  12. Enter device identification "Device ID" (assigned in first part of worksheet) for the position and/or channel being tested on the worksheet.
  13. On the worksheet, indicate if the console is to be certified for counting or generating live, dry, or both types of pulses, and also indicate if the pulse counters and generators are capable of counting and generating two-wire, three-wire, or both types of pulses.

7.11 Rangeability

7.11.1 Guidelines

In this procedure, a Radian comparator is used to simulate maximum detectable positive and negative meter errors and the console is checked to see if it is capable of determining the simulated error.

7.11.2 Procedure

  1. Simulate the maximum detectable positive error by setting the thumb wheel switches on the comparator according to the following formula:

    TWSe= TWSc × (100÷(100+e))

    where:

    • TWSe = thumb wheel setting to simulate error
    • TWSc = thumb wheel setting with no deliberate error
    • e = desired error in percent
  2. Use the formula above and the following example conduct a basic accuracy test:

    TWSc is set at 15.0000 for the basic accuracy test. To introduce an error of e = +3 percent (i.e. to emulate a meter under test which is 3 percent fast) the thumb wheels should be set to 14.56.

  3. Enter the console reading in the worksheet under the "true error" column and enter the maximum detectable positive error under the "calculated error" column.
  4. Repeat steps (1) to (3) for the maximum detectable negative error and enter the maximum detectable negative error in the "calculated error" column of the worksheet.

Note: The console is capable of determining the simulated error if the error difference is within the applicable tolerance (0.2% for energy meters).

8.0 Revisions

8.1 The purpose of revision 3 was to:

  1. Modify numbering and lettering due to the modification of sections 5 and 6 of S-E-01.
  2. Remove references to 5.2 (d)(i) through (xviii) and reword the specification to address these removals.

8.2 The purpose of revision 4 is to amend the procedure to address the new calibration console certification requirements of EL-ENG-12-01 and the current processes used for the certification of consoles. Most of the sections of the procedure P-E-01 (rev. 3) have been revised with minor editorials or major revisions.

The following list is not inclusive, but is meant to highlight a number of changes made to the procedure:

  1. The scope has been clarified and a Purpose section has been added.
  2. The Reference section has been revised.
  3. The definitions have been removed, as they are provided in EL-ENG-12-01.
  4. The Safety and Hazard section has been clarified.
  5. The Roles and Responsibilities section has been revised (this includes editorial changes).
  6. The Log Book and File section is now called Records.
  7. Significant changes have been made to the section on accuracy checks to address the new requirements.
  8. The maximum test voltage and current procedure has been removed.
  9. The test tables for the assessment of indicating instruments have been removed and are now included in EL-ENG-12-01.
  10. The section on statistical calculations has been removed.
  11. The figures showing the test setups have been removed from the procedure.
  12. The basic procedure for conducting accuracy tests has been revised to remove the diagrams and it was clarified that this is only an example of a procedure that can be used.
  13. The Test Position, Test Loads and Test Burden section has been significantly revised and is now called Console Configurations, Test Loads, Burdens and Burden Effects. The new section addresses sensitivity to the number of meters under test.
  14. The Sensitivity to the Number of Meters Under Test section has been removed.
  15. The regulation procedure has been significantly revised.
  16. The section containing the procedure for establishing errors for consoles with interchangeable reference meters has been removed.
  17. A new section for determining console uncertainty has been added to the procedure.
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