The purpose of this specification is to define the limits of error variation of measuring instruments under the influence of self-heating effects and their test methods. Specific error variation limits are set for Class 1 (Level 1) and Class 2 (Level 2) smart meters for different current strengths and power factors.
test step
Warm-up phase: First, the voltage circuits are powered under reference voltage conditions. This process should last at least 2 hours for class 1 smart meters and 0.5 hours for class 2 smart meters.
Current loading: Subsequently, the maximum rated current is quickly applied to the current loop without an initial current, and recording of the smart meter's error begins immediately.
Error monitoring: From the moment the current is applied, the instrument error shall be measured immediately at a power factor of 1 and the change in error over time shall be continuously monitored and an error change curve plotted. The entire test shall be maintained for at least one hour to ensure that the error fluctuation does not exceed 0.2 percent for any 20 consecutive minutes during this period.
Repeat Test: All the above steps should also be repeated at a power factor of 0.5 (inductive load condition) to fully evaluate the smart meter performance.
Cable requirements
The length of the cable used to connect the test equipment should be fixed at 1 smart meter, and its cross-sectional area should be designed in such a way that the current density is maintained at a constant level between 3.2 A/mm² and 4 A/mm², thus guaranteeing the validity and accuracy of the test results.
Key points
According to the provisions of Table 4, the increase in measurement error due to the self-heating phenomenon must be strictly controlled within the limits to ensure that the measurement data is true and reliable.
Through these detailed test procedures, we are able to accurately evaluate the effects of self-heating that the measuring instruments may experience in the actual working environment, and thus provide a more accurate measurement service. At the same time, this series of rigorous test standards reflects our high commitment to product quality and customer satisfaction.
