Energy meters are calibrated based on the energy meter accuracy class. The energy meter accuracy class is based on measurement accuracy in the electrical industry, which is a critical task as accurate measurement results are critical for the design, installation, maintenance, and repair of electrical systems. Whether in power systems, industrial automation, communications, and information technology or in household electrical equipment, precise measurements are required to ensure system stability and safety. The following article will introduce the relevant content of energy meter accuracy class in the electrical industry through several aspects.

1. What is Energy meter accuracy?

Energy meter accuracy refers to the difference between the result obtained by the measuring instrument and the actual value when the measurement is made. Energy meter accuracy class is one of the most important factors in various types of instruments, especially in fields that involve high-precision measurements, such as medical, industrial, and scientific research.

Measures of precision are usually calculated by standard deviation. Standard deviation is the difference between the mean of the sample data and the true value. The smaller the value, the higher the accuracy of the instrument, because the measured results are closer to the real value.

Here is the energy meter accuracy class according to IEC (International Electrotechnical Commission) and MID (Measuring Instruments Directive) classes only.

The actually available accuracy classes are for active energy meters:

class 2 energy meter (IEC 62053-21) equivalent to class A (MID EN 50470-3)

class 1 energy meter (IEC 62053-21) equivalent to class B (MID EN 50470-3)

Class 0.5 S energy meter (IEC 62052-22) equivalent to class C (MID EN 50470-3)

class 0.2 energy meter (IEC 62052-22)

For reactive energy meters:

Class 3 energy meter (IEC 62053-23)

Class 2 energy meter (IEC 62053-23)

Class 1 energy meter (IEC 62053-24)

Class 1 S energy meter (IEC 62053-24)

Class 0.5 S energy meter (IEC 62053-24)

2. What does the energy meter accuracy class with the letter “S” mean?

In the power system, electric energy is an important energy source, and the measurement accuracy of electric energy is related to the rational development, use, and distribution of benefits of energy. In order to ensure the accuracy of electric energy measurement, the power systems of various countries have formulated corresponding electric energy measurement standards. In China, the electric energy measurement standard is GB/T 17215.321-2008 “Electric Energy Measurement Accuracy of Electric Energy Meters”.

The energy meter accuracy class is divided into several grades, including 0.5, 1, 2, and S grades. Among them, S-level is the highest level of accuracy, and its accuracy index requirements are the most stringent, which can realize the very accurate measurement of electric energy. The test requirements for S-level accuracy of electric meters are as follows:

The error of the meter on the calibration point is not more than 0.1%;

Within the rated load range, the error of the meter does not exceed 0.1%;

The instantaneous error of the meter does not exceed 0.2%.

In addition to the ability to accurately measure electrical energy, the S-level accuracy of the energy meter also has good anti-interference performance. There are various interference sources in the power grid, such as electromagnetic interference, electromagnetic wave interference, voltage interference, etc. These interference sources will have a negative impact on the measurement accuracy of the meter. S-class energy meters have excellent anti-interference performance, can work normally and maintain measurement accuracy, and can guarantee energy meter accuracy even in strong electromagnetic interference environments.

 3. What are the factors that affect the energy meter accuracy?

4 Factors Affecting Energy Meter Accuracy

Temperature: The temperature of the environment in which the electric meter is used has a great influence on its accuracy. Too high or too low ambient temperature will lead to inaccurate measurement of the meter.

Power supply voltage: The energy meter accuracy is also affected by the power supply voltage. An unstable power supply voltage will increase the measurement error of the electric meter, and long-term use may also affect the life of the energy meter.

Power frequency: Variations in power frequency can also affect the energy meter accuracy. Unstable power supply frequency, especially when there are problems such as harmonics in the power supply system, will lead to measurement deviations of electric meters.

Factors of the energy meter itself: The quality, design, and manufacturing process of the meter itself will also affect its accuracy. Meters with poor quality will have measurement errors, and energy meters with unreasonable design and manufacturing processes will also affect the energy meter accuracy.

4. What is the calibration method for energy meter accuracy?

In order to ensure the accuracy and accuracy of the energy meter, it needs to be calibrated regularly. Verification methods include the following:

Direct comparison method: compare the meter to be calibrated with the standard meter to judge its error.

Standard resistance method: By using standard resistance for calibration, the error of the meter can be judged.

Standard voltage method: By using standard voltage for calibration, the error of the meter can be judged.

Standard current method: By using standard current for calibration, the error of the meter is judged.

It should be noted that before the calibration, it is necessary to ensure the accuracy and stability of the standard ammeter, standard resistance, standard voltage, standard current, and other equipment, so as not to affect the calibration results of the ammeter.

As a conclusion, the energy meter accuracy is very important to the calculation of power metering and tariffs. It is affected by factors such as temperature, power supply voltage, and power frequency. Regular calibration is required during use. Calibration methods include the direct comparison method, standard resistance method, standard voltage method, and standard current method, etc. Attention should be paid to the accuracy and stability of standard equipment.