Electric Energy Meter Verification Equipment Common Fault Analysis Strategy

1. INTRODUCTION Electric energy meter is a national mandatory measurement and measurement instrument. Its accuracy is directly related to the interests of millions of households. The electric energy meter verification device is used to verify whether the electric energy meter is accurate and reliable. Now, the verification devices used in measurement verification agencies and enterprises are mostly electronic products. It is difficult to repair them. However, as long as the cause of failure is carefully analyzed and summarized, some common faults can be solved by themselves.

2. Verification device working principle Under the control of the computer or keyboard, the program-controlled power supply provides the voltage and current required by the calibration meter and the standard energy meter; the standard meter sends the power energy pulse to the error calculation unit, and the error calculation unit acquires the data at the same time. Table pulse and calculate the error, the error calculated by the electric energy comparison method is displayed locally and sent to the computer for display and processing by the control center; the control center mainly completes the query error, monitors the output of the control voltage and current, displays the voltage, current, and power, processing Keys and other work; At the same time, the collected data is selected to the computer for display processing, verification of the working principle of the device shown in Figure 1.

3. Common fault analysis and processing methods 3.1 Faults in current and voltage 3.1.1 Faults in large-current output alarm Fault analysis: When the test current range is 30 (100) A three-phase energy meter, the current output is 100% Normal, when the test point is switched to 300%, the device alarms, prompting current alarm. Most of these phenomena are fault phenomena caused by excessive contact resistance of the current loop and a certain point contact in the current loop.

Troubleshooting: cut the current to the alarm position, and then adjust the potentiometer to make the current amplitude about 40%, to see if the current alarm, if it is normal, it can be caused by the poor contact of the current loop, you can find the current output line and Whether the current line of the table body is loose and rust oxidation occurs. According to the specific situation, the sanded paper can be used to polish the oxidation part so that the contact part is good, or replace the thick connection wire and tighten the loose bolt. The above treatment can completely solve the alarm problem of high current.

3.1.2 Failure analysis of a fault with no output current in one stall: In the verification work, it was found that when the 5(20)A meter was tested, the current was 0, the power was about 0.3, and the verification device did not alarm. It is found that there is no output in one gear of the current, which may be a problem with the control relay of a certain gear, or a problem with the shift register CD4094 and the driver chip 1413 of the control relay. Most of these phenomena occur when the power is being verified. Table, when the voltage and current are rising, caused by sudden power failure.

Troubleshooting: After finding such a fault, you can test whether the other current gear position is working properly. If it is normal, you can use the multimeter's DC voltage level to measure the current. If the protection diode 4007 of the gear drive coil has a DC voltage of about 24V, If it is normal, it can be concluded that the relay is bad, there is no DC voltage or is not normal, there may be a problem with the driver chip 1413, and the driver chip 1413 of the control relay may be replaced. If it is still not enough, the shift register CD4094 can be replaced. In the processing of such phenomena, it is found that the driver chip 1413 is most likely to be damaged.

3.1.3 Analysis of faults with no output voltage in one gear or all gears: When verifying a three-phase three-wire mechanical energy meter of 380V, it is found that there is no voltage output and cannot be verified normally. A three-phase four-wire energy meter. Most of the voltage alarms are caused by incorrect wiring of the energy meter. It is possible to check whether the wiring of the meter is correct. No output is caused by damage to the voltage output relay.

Troubleshooting: This type of fault is related to the voltage output short-circuit protection of the verification device. If the fault is removed, the output voltage can be restored to normal use. The voltage wiring should be connected to the voltage terminal of the energy meter. As long as the wiring is correct, such failures rarely occur. No output voltage failure, you can find the voltage output relay and voltage gear control relay whether there is a DC voltage 24V, and the related drive chip 1413 and shift register CD4094.

3.1.4 Failure Analysis of Voltage and Current Output Abnormalities and Large Change in Amplitude Faults: During the calibration process, an unexpected power failure occurs, and then 60% of the voltage and current are displayed when the verification device is used, and the display is still not displayed. Stable phenomenon. This kind of failure occurs mostly because the power supply voltage is low or the fluctuation is large and the three-terminal integrated voltage regulator block 7815, 7915 of the test power supply compensation part is related to the capacity of the large-capacity capacitor of the power amplifier.

Troubleshooting: The voltage and current output is abnormal. If the power supply quality is poor or the voltage is low, an automatic regulated power supply can be configured. The problem of selecting a regulated power supply of 1500W to 2000W can be solved. The three-terminal integrated voltage regulator block 7815 and 7915 can use the multimeter's DC voltage range to test whether the regulator's input and output are normal. Under normal circumstances, 7815 input DC 20V output 15V, 7915 DC input -20V output -15V.

3.2 Check the electronic table error over fault fault phenomenon analysis: verification found that a range is 5 (20) A, a constant of 1600 single-phase electronic energy meter error is about 4% error over tolerance. The occurrence of this phenomenon depends on whether the error is a serious overshoot or a small range of overshoot. This is crucial to the solution of the problem. Serious overshoot may be caused by improper voltage selection or by the problem of the meter itself. The out-of-tolerance can basically exclude the cause of the verification device, which is mostly caused by the error of the meter itself.

Troubleshooting: In case of serious overage, you can check whether the wiring of the verification device and the electronic watch is correct. If it is correct, the error is still bad, you can replace a piece of qualified electronic meter to test it. If the error is normal, you can conclude that the electronic meter has a problem. The small range of error error may be due to the fact that the error of the table is not good or the power factor is unbalanced. Usually, the problem of the verification device can be excluded.

3.3 Faults in the Communication Section 3.3.1 Fault Analysis in Communication with Computers: In the process of using the computer's verification software to check the meter, the phenomenon that the error of the meter is not read out suddenly occurs, and then the software is shut down and the computer is restarted. Not solved. The communication between the verification device and the computer is through RS232 to realize the communication function. There are three communication lines: RXD, TXD and GND. You can use serial debugging assistants and other debugging tools to determine the serial port fault. Sometimes the serial port of the computer works abnormally, which may cause abnormal communication with the verification device.

Troubleshooting: Phenomenon can be considered from two aspects, the first is whether the serial line is connected, the second is whether the hardware line is connected correctly, if you can use the serial port debugging assistant, send the voltage and current request command, normal should be able to receive the voltage The hexadecimal data of the electric current, should pay attention to the baud rate when the operation should set up with the verification device.

3.3.2 Fault Analysis with Keyboard Communication Abnormal Fault Analysis: The verification device that was used normally in the previous day. After the meter is connected, the voltage and current are raised with the keyboard. No response, and the verification software of the computer can be used normally after verification. phenomenon. The phenomenon is characterized by the keyboard can not control the verification device, you can check the keyboard +5 V power supply and GND is normal, and gradually determine whether the keyboard itself is working, then check the MCU RXD and TXD is connected, you can use a multimeter diode test test connection Whether to connect.

Troubleshooting: First determine the working status of the keyboard, if not normal can see whether the power supply is +5V, but this type of phenomenon is mostly RXD and TXD connection bad connection, or due to broken, you can use a multimeter to measure the connection of the connection State, the connection is normal, the problem can be solved.

3.4 Analysis of the standard table after the inspection of the power meter error serious over fault fault phenomenon analysis: the standard table inspection before the verification device can be used normally, after the standard table submitted to the verification device installed, check the three-phase four-wire table is found in the error About 60%, but also for a piece of the same meter error in about 62%, should be the standard table wiring error. Since the standard table is sent to the verification device after installation, the current terminal of the standard meter needs to be connected to the current secondary output line of the test power supply, and the voltage terminal of the standard meter should also be connected to the voltage terminal of the test power supply. , And the three phases of the voltage and current cannot be interchanged, and the wiring of the pulse output, and the wrong connection may lead to fault phenomena such as the verification device and the error being seriously bad.



Troubleshooting: Since it is a failure phenomenon that occurs after the inspection of the standard table, the connection of the standard table should be carefully identified before the inspection of the standard table, and this type of failure can be avoided.

4. Routine Maintenance Precautions 4.1 After the device is used, turn off the power switch, remove the voltage cable, and short-circuit the current terminal.

4.2 Maintain the cleanliness and temperature and humidity of the verification room. It is best to add a dust cover when the verification device is not in use.

4.3 If you do not use it for a long period of time, keep it on at least once a week.

5. Conclusion In summary, although the power meter verification device types are various, the basic principle is the same. If you are familiar with the working principle and internal circuits, you can basically eliminate the failure of the energy meter verification device in a timely and accurate manner.

References [1] Machinery Industry Occupational Skill Identification Guidance Center. Electrical Instrument Repair [M]. Beijing: Mechanical Industry Press, 2003.

[2] Ma Ruisong, et al. Metrological verification procedures for AC energy meter verification devices [M]. Beijing: General Administration of Quality Supervision, Inspection and Quarantine, 2006.

[3] Peng et al. Verification and maintenance of AC energy meter verification device [M]. Beijing: China Measurement Press, 1997.

About the author: Zhong Hua (1978—), Male, Hengyang, Hunan, Engineer of Metrology Test Verification Institute, Loudi City, Hunan Province, Research direction: metrological verification and management.