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 2 of 4)

7.3 Basic procedure for conducting accuracy tests (part 2 of 2)

7.3.2 Basic procedure for conducting demand accuracy tests

7.3.2.1 Guidelines
  1. Console demand reference meters are either external or internal. External reference meters are not an integral part of the console (e.g. reference meters connected to the secondary terminals of the standard position) and they directly display the required power functions. Internal reference meters are built-in or integral to the console. In this case, the power measurement is usually read on one of the console indicating instruments.
  2. Accuracy tests for consoles with an internal reference meter and an indicating instrument are conducted by visually comparing the readings on the reference meter with the readings on the certified standard in the MUT position (the test procedure is outlined in s. 7.3.2.7).
  3. There are two methods available for performing this test. In both cases, the test is performed by calibrating a certified standard and transformer combination in a MUT position, as if it were an energy meter being verified by the console reference meter.
  4. If the console has an input connection for the pulse output of an external watt-hour standard, the tests may be performed using the method in section 7.3.2.8, which is the preferred method as it is simple to perform, easy to set up, and error calculations are performed automatically. In this case, pulses are being counted by the reference meter and compared to the pulses counted by the certified standard in the MUT position.
  5. If the console does not have an input connection as stated above, the method in section 7.3.2.9 must be used. This test is a comparison between readings on the reference meter, and the readings on the certified standard in the MUT position. The test is performed by comparing the accumulation of energy on the reference meter with that of the certified standard. The two devices are set to the associated energy function of the demand function that is being tested.

Example

When testing for VA demand, the reference meter and the certified standard are both set to read VA-hours.

7.3.2.2 General setup
  1. Install the meters in all but one MUT position.
  2. Install the test socket in one MUT position and connect the certified standard to the voltage and current circuit using the appropriate leads. Ensure that the standard is connected appropriately for the type of test being performed, (e.g. single-phase or polyphase).
  3. Install one or more potential coils (for electro-mechanical meters) across the voltage terminals of the test socket. Potential coils must be the same as those in the meters being used as test burdens. For electronic meter certification, the actual meters are to be used where a burden is required.
7.3.2.3 Procedure for consoles using an internal demand reference meter and an indicating instrument
  1. Set the certified standard to measure the applicable power function that the console internal reference meter is measuring (watts, vars, VA avg., VA rms).
  2. Ensure regulators are in the circuit and switched on while performing the tests.
  3. Set the console to one of the demand test points determined pursuant to section 7.8 of EL-ENG-12-01.
  4. Energize the console and allow the load to stabilize. Switch on the regulators.
  5. Monitor both the indicating instrument (demand reference meter) and the certified standard in the MUT position.
  6. When the load is holding very stable, record the reading on the indicating instrument and the reading on the standard. A minimum of three readings are to be averaged during the assessment.
  7. Multiply the reading from the indicating instrument by the appropriate voltage and current ratio.

    Reading(MUT) = Reading(ref) × (Vstd÷Vref) × (Istd÷Iref)

    Where:

    • Reading (MUT) = the power measured by internal reference meter as shown on indicating instrument, and corrected for transformation factors due to PTs and CTs between internal reference meter and MUT
    • Reading (ref) = the power reading as measured by internal reference meter as shown on indicating instrument
    • Vstd = the nominal voltage at the certified standard in the MUT position
    • Vref = the nominal voltage at the internal reference meter and indicating instrument
    • Istd = the nominal current at the certified standard in the MUT position
    • Iref = the nominal current at the internal reference meter and indicating instrument
  8. The apparent error of the certified standard in the MUT position is determined by the following formula:

    Error(s) = ((Reading(std) − Reading(MUT))÷Reading(MUT)) × 100

    Where:

    • Error (s) = the apparent error of the standard in the MUT position
    • Reading (std) = the power reading on the standard in the MUT position
  9. Repeat steps (5) to (8) two more times to ensure consistent results. The three resultant "Errors" shall not differ by more than 0.05% in spread. If there is a spread of more than 0.05% then the resulting error is not conclusive due to the lack of repeatability. The three "Errors" shall be averaged to determine the final Error(s) at that particular demand test point. Record the error and test point on the Console Calibration section of the worksheets.
  10. De-energize the console and switch regulators off.
  11. Repeat steps (3) to (10) with appropriate burdens in the MUT positions for all applicable test points and MUT positions as determined pursuant to section 7.8 of EL-ENG-12-01.
7.3.2.4 Procedure for consoles using an external dedicated demand reference meter with input connections for counting pulses from an external reference meter
  1. Set both the dedicated reference meter and the certified standard in the MUT position to measure the applicable power function for the test points (watts, Vars, VA avg. and VA rms).
  2. Use a coaxial cable to connect the output of the reference meter to the external watt- hour standard input on the console.
  3. Set up the console to accept pulses from an external reference meter; the internal reference meter is now bypassed. This may need to be done by the console owner's technician if it is in a password-protected parameter database.
  4. Set up the comparator as described in section 7.3.
  5. Use regulators while performing the tests and ensure they are in the circuit and switched on.
  6. Set the console to one of the demand test points determined pursuant to section 7.8 of EL-ENG-12-01.
  7. Energize the console and allow the load to stabilize. Switch on the regulators and press the "start" button on the comparator.
  8. Record the error and test point on the Console Calibration section of the worksheets. De-energize the console and switch regulators off.
  9. Repeat steps (6) to (8) with appropriate burdens in the MUT positions for all applicable test points and MUT positions, as determined pursuant to section 7.8 of EL-ENG-12-01.
7.3.2.5 Procedure for consoles using an external dedicated demand reference meter without input connections for counting pulses from an external reference meter
  1. Set the dedicated demand reference meter and the certified standard in the MUT position to measure the associated energy function for the applicable power function being tested (watt-hour for watt demand, Var-hour for Var demand, etc.).
  2. Connect the input from the reference meter to one end of the BNC T connector.
  3. Connect the input from the certified standard in the MUT position to the other end of the BNC T connector.
  4. Connect the switch to the input end of the BNC T connector.
  5. Set the console to one of the demand test points determined pursuant to section 7.8 of EL-ENG-12-01.
  6. Reset both the dedicated reference meter and the certified standard in the MUT position to read zero.
  7. Energize the console and allow the load to stabilize. Switch on the regulators.
  8. Press the switch to start accumulation of energy on both the reference meter and the certified standard at the same time.
  9. After five to ten seconds, press the switch again on both the reference meter and the standard to stop the accumulation of energy. De-energize the console and switch regulators off.
  10. The apparent error of the standard in the MUT position is calculated by the following formula:

    Error(s) = ((Reading(std) − Reading(ref))÷Reading(ref)) × 100

    Where:

    • Error(s) = the apparent error of the standard in the MUT position
    • Reading (std) = the energy reading on the standard in the MUT position
    • Reading (ref) = the energy reading on the dedicated demand reference meter
  11. Record the error and test point on the Console Calibration section of the worksheets.
  12. Repeat steps (5) to (11) with appropriate burdens in the MUT positions for all applicable test points and MUT positions, as determined pursuant to section 7.8 of EL-ENG-12-01.
7.3.2.6 Formula

The error of the console at any of the demand test points is as defined in section 7.1.2.2 of EL-ENG-12-01.

Econs, Error of the Console = Esm, Apparent error of standard (and transformers) − Ec, Certified (or calculated) error of standard (and transformers)

7.3.3 Minimum duration of accuracy tests (EL-ENG-12-01, s. 7.1.3)

7.3.3.1 Purpose

The purpose of section 7.1.3 of EL-ENG-12-01 is to prescribe the minimum test time for performing accuracy tests for the verification of meters and the calibration of the console to ensure calibration console accuracy test results have a minimum resolution of 0.01%. Some calibration consoles automatically determine and display MUT errors. These consoles do not emit pulses from a reference meter; therefore, a minimum time limit is used to ensure the resolution is adequate.

7.3.3.2 Guidelines
  1. In the case of consoles that emit pulses from a reference meter, the minimum 10 000 pulse resolution is attained by applying the formula as specified in the Basic Procedure for Conducting Accuracy Tests.

    Note: The factor of 10 000 in the formula of step (11) of section 7.3.1.3 of the Basic Procedure for Conducting Accuracy tests is a minimum. It could be any integer value greater than 10 000. If a larger number is used, it must also be used as the set number of pulses expected from the console reference meter.

  2. Some consoles emit pulses from a reference meter, but the operator does not determine the test length by setting the appropriate number of pulses expected by the reference meter. The test length is determined in the test setup for any particular type of meter, based on the meter Kh and the number of disk revolutions required. A minimum of five (5) seconds per pulse interval of the light valve, and a minimum ten (10) seconds total test time is required. Therefore, if the test is set up to do only one pulse interval of the light valve (one disk revolution) instead of two, a minimum of ten (10) seconds is required between the start pulse and the stop pulse. A quick calculation should be performed to ensure that a minimum of 10 000 pulses are emitted from the reference meter.

    Example

    A console emits 14 500 pulses/second with 600 watts applied to the internal reference meter connected in the 120 volt, 5 amp secondary circuit. If a calibration test point is performed at 277 volts using the 360 volt tap and 50 amps using the 100 amp selector switch, the internal reference meter will be pulsing at a rate of: 14 500 × 277⁄360 × 50⁄100 = 5578 pulses/second.

  3. In the case of consoles that automatically determine and display MUT errors, a minimum of five (5) seconds per pulse interval of the light valve and a minimum ten (10) seconds total test time is required. Therefore, if the test is set up to do only one pulse interval of the light valve (one disk revolution) instead of two, a minimum of ten (10) seconds is required between the start pulse and the stop pulse.
7.3.3.3 Remarks

It is important that the minimum time be followed, since a shorter measurement period results in poor repeatability and an increased uncertainty of the results.

7.3.4 Console configurations, test loads, burdens and burden effects
(EL-ENG-12-01, ss. 7.2 and 7.3)

7.3.4.1 Purpose

The purpose of sections 7.2 and 7.3 of EL-ENG-12-01 is to establish which loads and burdens are required for carrying out performance and certifications tests pursuant to section 7.0 (metrological requirements).

7.3.4.2 Guidelines for console configurations
  1. Console calibration and certification is conducted with the console setup such that the meter current elements are connected in series. Consoles that energize meter elements from independent sources require each source to be calibrated and certified.
  2. When meters are installed on a test console, they burden transformers in the electrical circuits. Different meters introduce different levels of burden. The burden effects test is performed by measuring the error at a MUT position while installing the different types of burdens. The difference between the resulting errors are recorded and compared.
  3. The following are the four common console configurations typically used for verifying meters:
    1. Consoles using 1:1 current transformers to assess meters without potential test links or meters with test links closed at a test load of 240V, 50A and 0.5 power factor (e.g. single-phase 1.5 element meters).
    2. Consoles with multiple potential transformers that are used without 1:1 current transformers in circuit shall be assessed at a load of 120V, 50A, 0.5 power factor (e.g. intended to test meters with insufficient number of potential test links for a typical set up, such as a network meter with only one test link).
    3. Consoles used to test transformer-type meters only or transformer-type and self-contained meters that may be tested without the use of isolation transformers at a load of 120V, 2.5A, 0.5 power factor (e.g. polyphase 3-element transformer- type meters).
    4. Consoles used to test only self-contained meters that may be tested without the use of isolation transformers at a load of 120V, 50A, 0.5 power factor (e.g. polyphase 3-element self-contained meters with sufficient test links to allow testing without any isolation transformers in circuits).
  4. For situations described in (a) and (b) above, the tests are to be repeated at each MUT position. Therefore, all isolation 1:1 current transformers used with the multiple potential transformers are assessed for burden effects at each position, and all multiple potential transformers used on their own without the 1:1 current transformers are also assessed at each MUT position as applicable to the use of the console.
  5. For situations described in (c) or (d) above, the tests are to be conducted with the burdens in any one MUT position, with all the other applicable burdens in the other positions.
  6. If the console is to be used for both inductive and capacitive burdens at the same time, the console must be assessed for the combination of inductive and capacitive burdens. The assessment is conducted with the high capacitive burden installed in the position under test with high inductive burdens installed in all other positions. The assessment is then reversed, with the high inductive burden in the MUT position and the high capacitive burdens in all the other positions. These assessments are conducted at the MUT positions described in (4) and (5) above.
  7. If the current rating of the test loads required in the above configurations is higher than the rating of the meters to be assessed on the console, the test load to be used should correspond to the highest verification test current of the meter with the highest rated current. For example, a console that only tests meters rated with a maximum rating of 0.1 to 100 amps is required to be assessed at a test load of 25A instead of 50A. Nevertheless, it is important that the same load be used for each set of burden tests for valid comparison.
  8. If the console does not require any meters to be verified at a 0.5 power factor the console assessment is to be conducted at unity power factor.
7.3.4.3 Test burden (EL-ENG-12-01, s. 7.2.3)
  1. The burden causing an error that is closest to the middle of the spread of errors determined by installing various burdens is to be used as the general test burden for calibration assessments pursuant to section 7.8 of EL-ENG-12-01.
  2. The test load and burden used during this assessment that causes the greatest absolute error of the three assessments (i.e. capacitive, inductive and no burden) is to be used for all assessments pursuant to sections 7.4, 7.5 and 7.7, as applicable.
  3. If a console is used to assess meters having only capacitive or only inductive burden properties, the burden type that is not applicable shall be replaced by a burden that represents the most common burden for the meters types to be verified on the console. This burden shall be used for the console's metrological assessments.
  4. The test burden installed in the MUT position is to be connected in parallel with the Radian voltage circuit.
7.3.4.4 Apparatus for assessment

For the purposes of determining the meters to be used as test burdens, the following equipment is required:

  1. Reference standard (Radian).
  2. Test socket and leads.
  3. Comparator, light valve and associated cables as required in the Basic Procedure for Conducting Accuracy Tests.
  4. Appropriate test burdens (meters and/or potential coils (for electro-mechanical meters only)) as determined pursuant to the information provided in section 5.2.6 of EL-ENG-12-01.
  5. Shorting bars for all other MUT positions.
7.3.4.5 Procedure for the assessment of test burdens using 1:1 isolation transformers
  1. Install the highest inductive burden in the first MUT position in parallel with the Radian standard connected in the MUT position. Also install the equivalent burdens in all the other positions.
  2. Set the load and configuration to that specified in section 7.3.4.2(3) (a) above.
  3. Energize the console and record the resulting error of position one. De-energize the console.
  4. Repeat steps (2) and (3) for the remaining positions.
  5. Install a burden that represents the meters with the highest capacitive voltage burden in the first MUT position in parallel with the Radian standard connected in the MUT position. Also install the equivalent burden in all the other positions.
  6. Repeat steps (2) and (3) for the remaining positions.
  7. Remove the burden and install a burden that represents the meters with the lowest burden in the MUT position. Also install the equivalent burden in all the other positions.

    Note: The lowest burden may be represented by using zero burden (i.e. shorting bars and no additional potential burden).

  8. Repeat steps (2) and (3) for the remaining positions.
  9. For consoles that mix capacitive and inductive burdens at the same time, repeat the assessment with the highest inductive burden in the first MUT in parallel with the Radian standard. Install high capacitive burdens in the other test positions and repeat with the burdens exchanged after each position is assessed.
  10. Repeat steps (2) to (4).
  11. Repeat steps (1) to (10) for the load and configuration specified in section 7.3.4.2(3) (b) above.
  12. The burden (potential coil) that represents the meter type that causes the largest absolute error is the burden type that is to be used for all tests that require a single-phase burden (or burdens requiring the use of 1:1 CTs) in sections 7.4, 7.5 and 7.7 of the console requirements. The burden with the medium error is to be used for calibration pursuant to the console requirements of section 7.8. If there is no difference in error between the burden types, either type may be used.
7.3.4.6 Procedure for the assessment of polyphase transformer-type test burdens
  1. Install the highest inductive meter burden (potential coils) in one MUT position in parallel with the Radian standard connected in the MUT position. Install the equivalent burdens in all the other positions.
  2. Set the polyphase load to that specified in section 7.3.4.2(3) (c) above.
  3. Energize the console and record the resulting error. De-energize the console.
  4. Remove the meter burdens (potential coils) and install meter burdens that represent the meters with the highest capacitive voltage burden in the MUT position.
  5. Repeat steps (2) and (3).
  6. Remove the meter burdens and install meter burdens that represent those with the lowest voltage burden in the MUT position. The lowest voltage burden may be represented by using zero burden (i.e. shorting bars and no additional potential burden).
  7. Repeat steps (2) and (3).
  8. For consoles that mix capacitive and inductive burdens at the same time, repeat the assessment with the highest inductive burden in the MUT in parallel with the Radian standard. Install high capacitive burdens in the other test positions and repeat with the burdens exchanged.
  9. Repeat steps (2) and (3).
  10. The burden that represents the meter type that causes the largest absolute error is the type that is to be used for all tests that require a polyphase transformer-type burden in sections 7.4, 7.5 and 7.7 of the console requirements. The burden with the medium error is to be used for calibration pursuant to the console requirements of section 7.8. If there is no difference in error between the burden types, either type may be used.
7.3.4.7 Procedure for the assessment of self-contained test burdens
  1. Install the highest inductive meter burden (potential coils) in one MUT position in parallel with the Radian standard connected in the MUT position. Install the equivalent burdens in all the other positions.
  2. Set the polyphase load to that specified in section 7.3.4.2(3) (d) above.
  3. Energize the console and record the resulting error. De-energize the console.
  4. Remove the meter burdens (potential coils) and install meter burdens that represent the meters with the highest capacitive voltage burden in the MUT position.
  5. Repeat steps (2) and (3).
  6. Remove the meter burdens and install meter burdens that represent the meter burdens with the lowest voltage burden in the MUT position. Install the equivalent burden in all the other positions. The lowest voltage burden may be represented by using zero burden (i.e. shorting bars and no additional potential burden).
  7. Repeat steps (2) and (3).
  8. For consoles that mix capacitive and inductive burdens at the same time, repeat the assessment with the highest inductive burden in the MUT in parallel with the Radian standard. Install high capacitive burdens in the other test positions and repeat with the burdens exchanged.
  9. Repeat steps (2) and (3).
  10. The burden that represents the meter type that causes the largest absolute error is the type that is to be used for all tests that require a polyphase self-contained type burden in sections 7.4, 7.5 and 7.7 of the console requirements. The burden with the medium error is to be used for calibration pursuant to the console requirements of section 7.8. If there is no difference in error between the burden types, either type may be used.
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