Instrument inspection, calibration, and measurement report

Instrument inspection, calibration, and measurement report

Calibration Regulations for Electric Energy Meters

1、 Scope of application

This regulation is applicable to the calibration, subsequent calibration, and in-service inspection of various AC energy meters with a rated frequency of 50Hz or 60Hz, used in trade settlement, industrial metrology, energy management, and other fields. Including direct and indirect induction type energy meters, electronic energy meters, and smart energy meters.

2、 Reference files

1. GB/T 17215.321-2008: Special Requirements for AC Measuring Equipment Part 21: Static Active Energy Meters (Class 1 and 2)

2. GB/T 17215.322-2008: Special Requirements for AC Measuring Equipment Part 22: Static Active Energy Meters (0.2S and 0.5S Levels)

3. JJG 596-2012: Verification Regulations for Electronic AC Energy Meters

4. JJF 1071-2010: Rules for Writing National Metrology Calibration Standards

3、 Terminology and definitions

1. Energy meter: an instrument used to measure the energy consumed during a certain time interval and display the measurement results in numerical or pointer form.

2. Basic error: The error of the electric energy meter determined under reference conditions.

3. Starting current: The minimum current value that can cause the energy meter to start and continuously record.

4. Creep: When there is no current in the current circuit of the energy meter and the voltage applied to the voltage circuit is 115% of the rated value, the test output of the energy meter should not generate more than one pulse.

4、 Measurement characteristics

1. Basic error limit: Under different load currents and power factors, the basic error of the electric energy meter should not exceed the error limit specified in Table 1.

|Accuracy level | Power factor | 0.05Ib | 0.1Ib | 0.2Ib (0.5In) and above|

|---|---|---|---|---|

|0.2S|1.0|±0.4%|±0.3%|±0.2%|

|0.2S|0.5L|±0.5%|±0.4%|±0.3%|

|0.5S|1.0|±0.7%|±0.5%|±0.5%|

|0.5S|0.5L|±1.0%|±0.7%|±0.7%|

|1.0|1.0|±1.5%|±1.0%|±1.0%|

|1.0|0.5L|±2.5%|±1.5%|±1.5%|

|2.0|1.0|±2.5%|±2.0%|±2.0%|

|2.0|0.5L|±4.0%|±2.5%|±2.5%|

Instrument inspection, calibration, and measurement report

2. Starting current: The minimum current value that the energy meter can start and continuously record at the reference voltage and frequency should not exceed the value specified in Table 2.

|Accuracy level | Direct access | Indirect access|

|---|---|---|

|0.2S、0.5S|0.001Ib|0.0005In|

|1.0、2.0|0.002Ib|0.001In|

3. Creep: There is no current in the current circuit, and a reference voltage of 115% is applied to the voltage circuit. The test output of the energy meter should not generate more than one pulse within the specified time limit.

5、 Calibration conditions

1. Environmental conditions: temperature (23 ± 2) ℃; Relative humidity 45% -75%; There should be no strong electromagnetic fields, mechanical vibrations, or impacts that affect the measurement in the surrounding area.

2. Calibration equipment

Standard energy meter: The accuracy level should be at least two levels higher than the calibrated energy meter and should be within the validity period. If the calibrated energy meter is at level 0.5, the standard energy meter should be at level 0.05 or above.

Standard transformer: The transformation ratio error and phase error meet the requirements and are used in conjunction with standard and calibrated energy meters.

Verification device: The stability of output voltage and current, adjustment fineness and other performance indicators should meet the calibration requirements.

6、 Calibration Items and Methods

（1） Appearance and logo inspection

1. Appearance: Check that the shell of the electric energy meter is not damaged or deformed, the display screen is clear and complete, the button operation is flexible, and the wiring terminals are not loose or oxidized.

2. Marking: When viewing the nameplate of the electric energy meter, the name, model, manufacturer name, license mark and number for manufacturing measuring instruments, product standard, serial number, manufacturing year, reference voltage, reference current, maximum current, instrument constant, accuracy level, measurement unit and other information should be marked.

（2） Insulation resistance test

1. Testing equipment: using an insulation resistance meter with an output voltage of 500V.

2. Test location: Conduct tests between the voltage circuit and the current circuit, as well as between each circuit and the casing.

3. Testing method: Connect the output terminal of the insulation resistance meter to the tested part, apply a 500V DC voltage for 1 minute, and then read the insulation resistance value, which should not be less than 5M Ω.

（3） Communication voltage withstand test

1. Testing equipment: AC voltage withstand test device, with an output frequency of 50Hz and a sine wave voltage waveform.

2. Test location: Same as the insulation resistance test location.

3. Testing method: Apply the specified test voltage to the above areas, such as 2kV for basic insulation and 4kV for reinforced insulation, for a duration of 1 minute. During the test, there should be no abnormal phenomena such as breakdown or flashover.

（4） Basic error calibration

1. Wiring method: According to the type of energy meter and calibration equipment, correctly connect the standard energy meter, standard transformer, and calibrated energy meter to ensure that the wiring is firm and error free.

2. Test point selection: Select multiple load current points at different power factors (1.0, 0.5L, etc.), such as 0.05Ib, 0.1Ib, 0.2Ib (0.5In), 1.0Ib (In), Imax, etc.

3. Testing steps: Adjust the output voltage and current of the calibration device to the set values. After stabilization, read the readings of the standard energy meter and the calibrated energy meter, and calculate the error of the calibrated energy meter. Each test point is measured three times and the average value is taken as the measurement result for that point. The error calculation formula is: \ \ text {error} (\ \%)=\ \ frac {W-x - W-n} {W-n} \ \ times 100 \ \%, where W-x is the calibrated energy representation value and W-n is the standard energy representation value.

（5） Start the experiment

1. Experimental conditions: Under the reference voltage and reference frequency, the current circuit is activated with a starting current.

2. Test method: Observe whether the electric energy meter starts and continuously records within the specified time, which is generally 60 seconds.

（6） Stealth test

1. Test conditions: There is no current in the current circuit, and a reference voltage of 115% is applied to the voltage circuit.

2. Test method: Observe whether the test output of the electric energy meter generates more than one pulse within a specified time (such as 60 seconds).

7、 Calibration result processing

1. Calibration certificate: A qualified electric energy meter shall be calibrated and a calibration certificate shall be issued. The certificate shall include information about the electric energy meter, calibration items, calibration results, calibration date, calibration personnel, calibration unit, etc. The calibration results should provide the measurement values, error values, and conclusions on whether they meet the metrological characteristics requirements for each calibration item.

2. Calibration report: For electricity meters that fail calibration, a calibration report should be issued. The report should provide detailed information on the non-conforming items and measurement results, as well as an analysis of the reasons for the non-conforming items and recommendations. Unqualified energy meters should be repaired or replaced, and recalibration is required after repair.

8、 Return time interval

In general, the interval for recalibration of electric energy meters is 1-3 years. For electric energy meters that are used in harsh environments, frequently used, or require high measurement accuracy, the interval for recalibration can be appropriately shortened; For electric energy meters with good stability and low frequency of use, the interval for recalibration can be appropriately extended after evaluation, but not exceeding 5 years at most. If any abnormal phenomena are found in the electric energy meter during use, it should be calibrated in a timely manner.