Analysis of Common Operational Fault Causes in Smart Electricity Meters

With the continuous development of smart grids, smart electricity meters are being increasingly widely applied, and various types of operational faults in smart meters are frequently encountered in energy measurement work. This paper analyzes the causes of smart meter failures and proposes corresponding solutions, using several actual operational fault cases as examples.

1. Black Screen
A black screen refers to a powered meter with no display, which is the most commonly occurring fault in field-operating smart meters. Upon removing and testing such faulty meters, it is found that the capacitor at position C2 on the DCDC sub-board is damaged, the voltage regulator chip on the power supply board is blown, or the UN neutral wire has detached. The causes of this black screen fault are analyzed as follows: instantaneous overvoltage on the circuit (such as lightning strikes or power grid fluctuations) or high-order harmonics generated by complex operating environments can damage capacitors and blow out voltage regulator chips; improper operation not following the manufacturing process can result in poor soldering or neutral wire detachment.

2. Garbled Display
Garbled display refers to the phenomenon where the LCD screen of a smart electricity meter shows missing strokes. Possible causes include poor soldering at the LCD pins or the meter being installed outdoors and exposed to prolonged high-temperature solar radiation. For instance, a company's three-phase smart meter displayed the total forward active energy as 702,610.88 kWh, peak period energy as 700,451.96 kWh, peak-time energy as 700,987.42 kWh, flat-rate energy as 700,551.59 kWh, and off-peak energy as 700,619.91 kWh. Under normal conditions, total forward active energy should equal the sum of peak, peak-time, flat-rate, and off-peak energies. However, this equation did not hold for this meter. The last eight digits of the barcode displayed on the LCD were 75517684, whereas those on the nameplate were 05517684.

This indicates that the LCD display had missing strokes—where the digit "0" was incorrectly displayed as "7," confirming a garbled display fault. When the meter was read on-site using a handheld meter reader, the total forward active energy was recorded as 002,610.88 kWh, peak energy as 000,451.96 kWh, peak-time energy as 000,987.42 kWh, flat-rate energy as 000,551.59 kWh, and off-peak energy as 000,619.91 kWh. The sum of the individual period readings matched the total, further confirming the garbled display diagnosis. The primary cause of this fault was determined to be prolonged exposure to high-temperature solar radiation due to the meter's outdoor installation.

3. Inability to Read Energy Data
This fault typically refers to the appearance of the "←" symbol (indicating reverse power flow) in the lower-left corner of the LCD screen, with the total forward active energy reading as zero and the reverse active energy showing a non-zero value. Investigation revealed that the main cause was incorrect meter wiring, and the actual energy consumption equaled the reverse active energy reading. After correcting the wiring error, the meter resumed normal operation.

4. Battery Under-Voltage
Single-phase and three-phase smart electricity meters are equipped with internal clock batteries that power the internal clock chip. Three-phase meters also have a battery for power-off meter reading, located behind the programming door on the meter panel. When a battery under-voltage fault occurs, the meter’s alarm light remains constantly lit, and a low-power symbol appears on the LCD. On-site handling involves removing the seal from the panel door, opening the door, taking out the battery, and measuring the voltage between its positive and negative terminals using a DC voltmeter. If the voltage meets specifications, the battery should be reinstalled and repositioned to ensure good contact; if the voltage is below the rated value, the battery must be replaced.

5. Fast Registering (Over-registering)
A user’s single-phase smart meter showed a sudden increase in energy reading. On-site testing with a calibration instrument showed the meter was within acceptable error limits. Laboratory testing after removal also confirmed the meter met standards, but the pre-calibration reading was 4,505.21 kWh and the post-calibration reading was 4,512.32 kWh—indicating 7.111 kWh was recorded during the test, whereas a typical single-phase meter test consumes only about 1 kWh. This confirmed the fault of "fast registering."
Analysis revealed that the CPU supply voltage was significantly higher than the designed 5V, causing abnormal read/write operations on the I2C bus. Further inspection of the power supply circuit identified a damaged capacitor C2. Possible causes of capacitor damage include instantaneous high voltages from grid fluctuations or lightning strikes, and high-order harmonics from complex electrical environments.

6. Comprehensive Analysis
Smart electricity meters are multifunctional devices that extend beyond basic energy measurement to include information storage and processing, real-time monitoring, automatic control, and data interaction. They meet the needs of energy measurement, marketing management, and customer service. However, their primary function remains accurate energy measurement, which must be both precise and stable. Therefore, in addition to fully utilizing energy acquisition systems to monitor the operational status and abnormal events of smart meters, it is essential to analyze the root causes of meter failures and actively implement improvement measures.

Based on the analysis of operational fault cases, the main causes of meter failures are summarized as follows:

(1) Environmental influences, including electromagnetic interference, harmonics, high voltage, lightning strikes, electrostatic discharge, excessive temperature and humidity, high-frequency electromagnetic fields, and electrical fast transient (EFT) pulses.

(2) Poor component quality, including batteries, CPUs, LCD screens, relays, varistors, capacitors, metering chips, voltage regulators, clock chips, crystals, 485 optocoupler diodes, and carrier communication modules.

(3) Software faults, including system crashes, sudden changes in energy display, and clock errors.

(4) Workmanship issues, including substandard welding techniques by meter manufacturers (leading to cold or loose solder joints) and incorrect wiring during installation by power supply companies.

To address these failure causes, the following measures can be taken:

(1) Strengthen component selection to ensure smart meters operate reliably even under extreme environmental conditions.

(2) Enhance software testing to improve the software's error prevention and anti-interference capabilities.

(3) Improve quality supervision of workmanship, effectively monitoring and evaluating both internal assembly quality and on-site installation practices.