Today, we'd like to introduce a national invention patent—an online verification method for digital energy meters. This patent was applied for by the State Grid Chongqing Electric Power Research Institute and was granted authorization on December 25, 2018.
Content Description
This invention relates to the field of electricity meter calibration equipment, and in particular to an online calibration method for digital electricity meters.
Background of the Invention
Currently, the national investment in the construction of digital substations is continuously increasing, and the demand for digital substation energy meters is also increasing. The application of electronic voltage and current transformers and intelligent primary equipment has made digital energy meters with voltage and current signals input via Ethernet digital signals based on the IEC61850 protocol an important device for energy metering in digital substations.
Although some domestic research institutions have developed corresponding calibration equipment, the calibration methods and devices vary widely and are not standardized, and their technical specifications are not yet clearly defined. In digital substations, electronic instrument transformers output IEC61850-9-1 digital signal frames. Digital energy meters receive these frames and directly perform mathematical calculations to determine the electrical energy. In traditional substations, electromagnetic instrument transformers output analog voltage and current signals, which the energy meter converts into digital values to calculate the electrical energy. The principles and interface methods of electronic instrument transformers and digital energy meters have undergone fundamental changes. Currently, there are no specific verification regulations for digital energy meters. Therefore, in practical engineering applications, the verification of digital energy meters generally refers to the accuracy verification of electronic multi-functional energy meters at the load point as specified in JJG596 "Verification Regulations for Electronic Multi-functional Energy Meters". Existing verification methods have significant drawbacks. During verification, voltage and current signals need to be separately led out from the merging unit to a reserved verification interface, and then connected to a small switch. The signal entering the energy meter from the merging unit is then pulled out and connected to the fiber optic converter. However, the digital energy meter will lose signal and stop metering during the operation of the converter, resulting in metering loss.
Therefore, an online verification method for digital energy meters is needed.
Summary of the Invention
The purpose of this invention is to provide an online verification method for digital energy meters.
Flowchart of the online verification method for digital energy meters of the present invention
The objective of this invention is achieved through the following technical solution: This invention provides an online verification method for digital energy meters, comprising the following steps: S1: setting an energy meter terminal interface and a reserved verification interface on the digital energy meter; S2: connecting one end of the fiber optic converter to the digital energy meter terminal interface, connecting the other end of the fiber optic converter to a merging unit for sampling the current and voltage values of the digital energy meter, and transmitting the current and voltage values of the digital energy meter to the data processing module.
S3: Connect one end of the fiber optic converter to the reserved verification interface, and the other end of the fiber optic converter to the calibrator. Sample the current and voltage values of the calibrator and transmit the current and voltage values of the calibrator to the data processing module. S4: Calculate the measurement error of the digital energy meter through the data processor in the data processing module. S5: Output the measurement error.
The measurement error is achieved through the following steps:
S41: Calculate the active and reactive power of the digital energy meter based on the current and voltage values of the digital energy meter;
S42: Calculate the active and reactive power of the calibrator based on the calibrator's current and voltage values;
S43: Calculate the difference in active power between the digital energy meter and the calibrator respectively; calculate the difference in reactive power between the digital energy meter and the calibrator respectively.
S44: Determine whether the difference between active power and reactive power is greater than the preset threshold at the same time. If so, determine that the digital energy meter to be tested is abnormal.
S45: If not, then the digital energy meter to be tested is normal, and the active power difference and reactive power difference are output.
The preset threshold is between 0.1% and 0.3% of the active and reactive power of the calibrator.
Due to the adoption of the above technical solution, the present invention has the following advantages: The non-destructive on-site verification device for digital energy meters provided by the present invention overcomes the verification drawbacks of existing verification devices. By transmitting the voltage and current signals led out from the merging unit to the reserved verification interface, and then transmitting them to the verification instrument through the fiber optic converter, the on-site error verification of the digital energy meter without interruption of operation is realized, avoiding the measurement loss caused by the loss of signal and the cessation of measurement during the verification process of the digital energy meter.
Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained from the following description and claims.
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