Interlaboratory test results comparisons for active and reactive energy meter

The article is dedicated to the organization and performance of bilateral interlaboratory comparisons of test results for active and reactive energy meter. Interlaboratory comparisons of test results are presented. Evaluation of the laboratory test results bias is provided by means of functioning statistics E n criterion. Analysis and conclusions concerning laboratory competence are obtained.


Introduction
Billing electricity meters, technical means of electric energy consumption control and manage- To ensure the accuracy of active and reactive energy consumption measurements during compliance with the requirements of the Technical Regulations assessment [1] , electricity meters are tested in the accredited according to the requirements [2] laboratories. National Accreditation Agency of Ukraine (NAAU) evaluates meeting the requirements of [2] by testing and calibrating laboratories.
This standard requires laboratories to have a quality assurance system for test and/or calibration results.
If this is appropriate, laboratories should monitor their results compared to other laboratories' results.
This monitoring should be planned and reviewed, and include participating in proficiency testing (PT) and interlaboratory comparisons other than proficiency testing.
NAAU considers PT a necessary tool for competency demonstration and maintaining laboratories' technical quality and requires that the laboratories participate in such TPs before and after accreditation [3] . PT is the participants functioning conformity assessment according to the established requirements by means of ILCs [3] . ILCs are the organization, performance, and measurements or tests assessment of the same or similar sample testing by two or several laboratories according to the set requirements [4] .
ILCs are widely used for particular tasks and are more often used at the international level. ILCs aim to assess providing by laboratories specific measurements or tests and constant laboratory activities monitoring, identifying problems and initiating actions for their solving by the laboratories, establishing the efficiency and comparability of test or measurement methods, and identifying differences between laboratories. ILCs guarantee reliable test (measurement) results not only for laboratory and metrological services customers but also for inspection and accreditation bodies and other organizations which set the requirements for laboratories [4] . ILCs are an urgent task for calibrating laboratories.

SE «Ukrmetrteststandart» (Provider) performed
ILCs round № 1 for testing active and reactive energy from December 2022 to January 2023. ILCs were organized according to [2,4] standards on order for test- ILCs program was realized according to requirements [4] . Provider -testing laboratory (TL 1) and Participant -testing laboratory (TL 2) took part in ILCs.
Testing was performed in normal conditions according to [5,6] .
TL 1 applied the direct measurement method during active and reactive energy meter testing. TL 2 also applied the direct measurement method [5,6] .
Measurement uncertainty evaluation in calibration was performed according to requirements [7,8] .
TL 1 provided ILCs results, including measurement uncertainty as a test report. TL 2 provided ILCs test report and measurement uncertainty the same as TL 1. Testing results of the meter as a reference sample (laboratories measurement results bias D lab , their expanded uncertainties U lab and criterion value E n ) are presented in Table 1 and Fig. 2 with symmetrical phase loading ABC with active electric energy measuring (I b = 5 А, U n = ⋅ 3 220 380 / V, PF = 1); in Table 2 and Fig. 3 with one phase loading A with active electric energy measuring ( I b = 5 А, U n = 220 V, PF = 1); in Table 3 and Fig. 4 with sym-  (1), where x TL2 is the measured value provided by TL 2;

ILCs calibration results
x TL1 is the measured value provided by TL 1.
TL 2 measurement results evaluation was carried out using E n criterion calculated by the formula [9,10] : U TL1 is expanded measurement uncertainty calculated by TL 1.