The actual inspection of the electric energy meter sent by the manufacturer is mainly carried out from the following aspects.
Namely: five aspects: mechanical requirements, climatic conditions that can be adapted, electrical requirements, electromagnetic compatibility, and accuracy requirements.
These five aspects are clearly defined in the national standard "Class 1 and Class 2 Static AC Active Energy Meter" (GB/T17215-1998).
Some of the test and inspection items in the regulations are generally conditional inspections by municipal and county-level power supply enterprises, but there are quite a few projects that do not yet have conditional inspections. The following will give a brief description of the places to be noted and the solutions.
The vast majority of the mechanical requirements can be checked by visual inspection and simple test methods. Such as: four-proof (anti-shock; anti-high temperature; anti-flame spread; anti-solid foreign objects, dust and water entry); lead seal is convenient and reliable (only after the lead seal is damaged can you touch the internal parts of the instrument); the terminal should have enough Insulation characteristics and mechanical strength; the structure and assembly of the watch case should be able to ensure that the non-permanent deformation does not hinder the normal operation of the instrument; the nameplate, wiring diagram, terminal signs meet the requirements, etc. These requirements are the basic requirements to ensure the safe operation of the energy meter, and can be observed and identified based on experience. Selection must not be ignored. In particular, the terminal block should be made of flame retardant materials, such as injection type phenolic resin; when the shell is made of ABS engineering plastics, it should be checked whether it is flame retardant; the shell must not have obvious deformation affecting the sealing characteristics and the relative displacement of internal components.
Accuracy requirements include inspections of changes in current and power factor, voltage changes, frequency changes, start-up tests, creeping tests, and word-travel tests. Generally, city-level and county-level power supply companies can perform inspections. Electronic energy meters generally have better linearity within the load range specified by the regulations, but the actual accurate calculation of the load range of meters from different manufacturers is very different. Because the actual load current on site changes frequently, the load can be accurately calculated The wider the range, the better the load characteristics of the table. In some rural areas, power grid voltage fluctuations are relatively large. Pay attention to check the error of the energy meter under the condition of the voltage fluctuation limit. Especially the light load error at low voltage and whether the power meter is strong. Check the DC power supply voltage in the meter can not fall below the working voltage of the calculator and chip, the ripple of the DC power supply can not increase significantly.
Accuracy requirements also include, such as harmonics, external magnetic induction, high-frequency electromagnetic field effects, etc. Generally, city-level and county-level power supply enterprises do not have the conditions for inspection, so please ask the provincial electric power laboratory for inspection.
Power consumption check for electrical requirements, including voltage lines and current lines. After measuring the voltage, current and load impedance of the energy meter with a transformer calibrator, calculate the power consumption of the energy meter at the rated voltage and rated current. This method is both accurate and convenient; the effects of power supply, voltage drop and short-term interruption, and self-heating can be simulated on the calibration table of the energy meter; short-term overcurrent will affect the inspection, and it is more difficult to strictly follow the definition of the regulations. Under 2 times the maximum current, gradually extend the time to detect the temperature rise (current terminal and sampling resistance) and error of the energy meter. This can understand the damage degree of the energy meter after overload.
In order to prevent the voltage of a certain phase from being burned out due to the imbalance of the load after the neutral point of the low-voltage power supply line is disconnected, the input voltage of the single-phase electricity meter is raised to 420V. After 4 hours, the rated voltage Check the energy meter under voltage should be qualified
(Someone should be on duty during the test, pay attention to safety, and immediately turn off the power to check for any abnormalities).
Climatic conditions and electromagnetic compatibility characteristics:
Both of these are important for electronic energy meters. In particular, the electromagnetic compatibility characteristics have a very serious impact on electronic energy meters, and the tables with poor electromagnetic compatibility characteristics often have "crash", "flying characters" and other phenomena in the field operation, and even the internal electronic components are damaged. This is an important characteristic of electronic energy meters that is different from mechanical energy meters. There are 5 items in the EMC test, namely: electrostatic discharge test, high-frequency electromagnetic field test, electrical fast transient burst test, surge test, and radio interference suppression test. Among them, the surge and pulse group are relatively close to some transient conditions in the power grid. It is recommended that conditional prefecture-level and county-level power supply companies purchase corresponding equipment and conduct spot checks on the energy meter.
In addition, it should be noted that due to the mechanical calculators of electronic watches, the card word problem has not been fundamentally solved in principle. Mainly through the selection of a good manufacturing process calculator and strict selection when entering the factory to ensure the quality of the whole meter. Therefore, pay special attention to the quality of the calculator. The stepper motor is shielded to prevent electromagnetic interference. The shell uses aluminum alloy brackets, fine gears, no burrs, materials that are not easily deformed, self-lubricating characteristics, strong magnetic characteristics of the stepper motor, and precise processing, which can reduce the problem of card words. Pay attention to carefully check and understand. The second is to carry out the word check. In order to more strictly assess the quality of the calculator and ensure that the energy meter installed on the site can be calculated correctly within the voltage allowable range, it is recommended to use the lowest (not considering transient) voltage that may occur in the local power grid for the word walk test.
Spot check of the energy meter in operation
The above inspection still cannot fully guarantee that there will be no problems after the energy meter is installed in the power grid. Therefore, after installation and operation for a period of time, spot checks must be carried out. The time interval and ratio of spot checks can be determined according to the quality of the energy meter in operation. The same batch of energy meters from the same manufacturer, with small failure rate, small error change and high qualification rate, can reduce the proportion of random inspection and the time interval of random inspection. Under normal circumstances, the sampling rate of the first-selected manufacturer's products within six months cannot be less than 5%. The rate of spot checks within one year cannot be less than 10%. If the quality is stable and the error variation is small, the proportion of spot checks can be reduced, but at least 1% must be spot-checked each year to monitor the changes in the quality of the energy meter over time. Extend the selection of the purchase of the energy meter to the entire use process, and further improve the purchase level by monitoring the situation in use.
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