5.1.1 Reference Standards, shall be maintained at the appropriate Reference Temperature within a tolerance of ±2C.

5.1.2 Save in so far as it is necessary to comply with the accuracy requirements of this Code of Practice, Reference Standard CTs and VTs need not be maintained at a Reference Temperature in accordance with 5.1.1 where it is impracticable.

5.2.1 Reference Standard(s), other than Reference Standard CTs and VTs, shall, unless its measurement traceability is maintained by radio communication, be verified at an Accredited Laboratory at intervals dependent on the specification(s) but in no case less frequently than at intervals of 24 months.

5.2.2 Reference Standard CTs and VTs shall be calibrated by an Accredited Laboratory at intervals not exceeding 5 years. Where records are made available to the Technical Assurance Agent, which show either a negligible or predictable deviation from previous calibrations, the Technical Assurance Agent may in such a case permit the interval between such calibrations to be increased.

5.3.1 During periods of use of a Reference Standard (i.e. between calibrations at Accredited Laboratories) satisfactory evidence shall be produced and made available to the Technical Assurance Agent to substantiate the stability of that Reference Standard.

6.1.1 AC/DC Transfer Standards shall be maintained at the appropriate Reference Temperature within a tolerance of ±2C.

6.2.1 AC/DC Transfer Standards shall be verified at an Accredited Laboratory at intervals dependent on their specifications but in no case less frequently than at intervals of 24 months.

6.2.2 Where records are made available to the Technical Assurance Agent, which show either negligible or predictable deviation from previous calibrations, the Technical Assurance Agent may in such a case permit the interval between such calibrations to be increased up to an interval of 5 years.

7.1.1 Save in so far as it is necessary to comply with the accuracy requirements of this Code of Practice, AC Transfer Standards need not be maintained at a given temperature.

7.2.1 AC Transfer Standards need not be verified at an Accredited Laboratory provided that they have been calibrated in accordance with 7.2.2 or 7.2.3.

7.2.2 AC Transfer Standards shall be calibrated against Reference Standards or AC/DC Transfer Standards at monthly intervals.

7.2.3 Where records are made available to the Technical Assurance Agent, which show either a negligible or predictable deviation from previous calibrations, the Technical Assurance Agent may in such a case permit the interval between such calibrations to be increased up to an interval of 6 months.

7.3.1 Where any AC Transfer Standard is used for on-site calibration or testing it should be calibrated before and after use. Neither the period from calibration to use nor the period from use to next calibration shall exceed one week.

7.4.1 When an AC Transfer Standard is calibrated and is found to be outside its specification, the reason shall be investigated and the occurrence reported to the Technical Assurance Agent within 3 working days of its discovery. Notification shall be given to the Technical Assurance Agent of the details and results of the investigation. The results of the investigation shall, inter alia, show:-

8.1.1 Save in so far as it is necessary to comply with the accuracy requirements of this Code of Practice, Working Standards need not be maintained at a given temperature.

8.2.1 Working Standards need not be verified at an Accredited Laboratory provided that they have been calibrated in accordance with 8.2.2 or 8.2.3.

8.2.2 Working Standards shall be calibrated against Reference Standards or Transfer Standards at monthly intervals.

8.2.3 Where records are made available to the Technical Assurance Agent, which show either a negligible or predictable deviation from previous calibrations, the Technical Assurance Agent may in such a case permit the interval between such calibrations to be increased up to an interval of 6 months.

9.1.1 This Code of Practice does not require the Standards of any Meter Operator Agent to be maintained or used at any one location.

9.2.1 Reference standards and AC/DC Transfer Standards shall not be Mobile Standards and shall remain in one location as far as possible and only be moved for verification at an Accredited Laboratory.

9.2.2 AC Transfer Standards and Working Standards may be Mobile Standards.

10.3.1 Meters shall be calibrated such that the overall accuracy is within the percentage error limits as defined in Table 1 (for Active Energy Meters) or as appropriate Table 3 (for Reactive Energy Meters). The overall uncertainty of measurement of the calibration shall not exceed the limits specified in Tables 1 or 3 as appropriate.

10.3.2 All initial calibrations of Meters shall be performed in a laboratory or test house (including any Meter manufacturer's works).

10.3.3 The reference conditions for influence quantities and voltage and current balance shall be as in the appropriate Meter specification or for Class 2.0 Active Energy Meters as are set out under the Electricity Act 1989.

10.4.1 Meters shall be on-site accuracy tested to demonstrate that the overall accuracy is within the percentage error limit defined in Table 2 (for Active Energy Meters), or Table 4 (for Reactive Energy Meters). The overall uncertainty of measurement of the on-site accuracy test shall not exceed the limits specified in Table 2 or 4 as appropriate.

10.4.2 For any Active Energy Meter an on-site accuracy test may performed by an injection test or at a prevailing load.

10.4.3 For any Reactive Energy Meter an on-site accuracy test may performed only by an injection test.

10.4.4 If any on-site accuracy test shows that the Meter is outside the required error limits then either:

10.5.1 Reactive Meters with a declared higher accuracy than class 2.0 are only required to meet the limits for class 2.0 Meters as in Tables 3 and 4.

10.5.2 Phase-advanced Reactive hour (PARh) Meters shall be calibrated and on-site accuracy tested in their normal connection configuration. The accuracy limits in Tables 3 and 4 shall apply to PARh Meters.

12.1.1 Initial calibration

12.1.2 Periodic testing

12.2.1 Initial calibration

12.2.2 Periodic Testing

12.3.1 Initial testing

15.1.1 A permanent signed record of each calibration and test of Standards employed in relation to Metering Equipment under this Code of Practice shall be maintained by the Meter Operator Agent.

15.1.2 Such records shall include an overall accuracy and uncertainty of measurement statement for the relevant Standard. Uncertainty should be determined using the current NAMAS directive.

15.1.3 Where Standards are used on-site the overall accuracy and uncertainty measurements shall be as determined in a laboratory.

15.2.1 Each Meter Operator Agent shall ensure that the relevant laboratory or test house makes available on the request of the Technical Assurance Agent all test reports, records and certificates which are required by this Code of Practice for inspection by the Technical Assurance Agent.

15.2.2 The results of all calibrations and on-site accuracy tests performed on Metering Equipment shall be retained as permanent signed records. The Meter Operator Agent shall ensure that such records are made available on request to the Technical Assurance Agent.

15.2.3 Each Meter Operator Agent shall ensure that the relevant records relating to quality assurance procedures in relation to 16 below shall be made available on request to the Technical Assurance Agent.