What is the principle of smart meter overdue tripping?

The principle of smart meter overdue tripping is mainly based on four core links: electricity monitoring, cost calculation, balance comparison, and tripping control, combined with hardware protection and software logic, to achieve automated power-off function. The following are the specific principles and processes:

1、 Electricity monitoring and data collection

Real time electricity consumption record

Smart meters use built-in current transformers (CTs) and voltage sampling circuits to monitor the current and voltage values of users' electricity consumption in real time, and calculate instantaneous power (power=voltage x current).

For example, when a household uses electricity, the electricity meter will continuously record the power consumption of devices such as air conditioners and refrigerators, and accumulate it into the total electricity consumption (unit: kilowatt hour, kWh).

Data Storage and Updating

The electricity meter stores the collected electricity consumption data in its internal memory and updates the remaining electricity or electricity balance periodically (such as every minute).

Remaining power=Initial recharge power - Used power;

If the prepaid model is adopted, the remaining electricity fee is equal to the initial recharge amount minus (the amount of electricity used multiplied by the unit price).

2、 Cost calculation and balance comparison

Ladder electricity price adaptation

Some smart meters support tiered pricing function, which calculates fees based on electricity consumption segments. For example:

First tier: 0-200kWh, unit price of 0.5 yuan/kWh;

Second tier: 201-400kWh, with a unit price of 0.7 yuan/kWh;

The electricity meter will automatically switch the unit price based on real-time electricity consumption to ensure accurate cost calculation.

Balance threshold setting

Users or power suppliers can preset trip thresholds (such as remaining electricity costs ≤ 10 yuan or remaining power ≤ 5kWh). When the balance is below the threshold, the electricity meter triggers a warning or trips.

Warning method: The electricity meter screen displays "insufficient balance", the buzzer sounds an alarm, or a reminder is sent through SMS/APP push.

3、 Trip control mechanism

Hardware trip structure

The smart meter integrates a trip relay (electromagnetic or electronic) internally, and its control circuit is connected to the main chip. When the balance is insufficient, the main chip sends a trip signal and the relay acts to cut off the circuit.

Electromagnetic relay: It disconnects the circuit by attracting and closing the contacts with an electromagnet, with a fast response speed (in milliseconds).

Electronic relay: using semiconductor devices (such as thyristors) to control on and off, with no mechanical wear and longer lifespan.

Software Logic Process

Step 1: The electricity meter continuously monitors the remaining power/electricity bill and compares it with the threshold.

Step 2: If the balance is ≤ the threshold, enter the "warning stage" and trigger the sound and light reminder.

Step 3: If the user fails to recharge in a timely manner and the balance continues to drop to the "trip value" (usually 0 or lower), the main chip of the electricity meter outputs a trip command.

Step 4: The relay activates to cut off the user's power supply, and the meter screen displays the words "tripped" or "overdue".

Anti misoperation trip design

Delay tripping: Some meters are equipped with a delay function (such as a 30 minute delay tripping when the balance is 0) to avoid frequent power outages caused by short-term insufficient balance.

Anti interference protection: By using software filtering algorithms to eliminate the interference of instantaneous voltage fluctuations or data acquisition errors, it prevents false tripping.

4、 Power restoration and data synchronization

Automatically restore power after recharging

After users recharge online (Alipay, WeChat) or offline (business hall), the power supply system sends the recharge information to the electricity meter through the communication module (such as 4G, NB IoT).

After receiving the recharge instruction, the electricity meter updates the remaining power/electricity fee and controls the relay to close, restoring power supply.

If there is a communication failure, some meters support "local power restoration": users can manually restore power by pressing the power restoration button on the meter (ensuring that the balance has been updated).

Data synchronization and reconciliation

After each recharge or trip of the electricity meter, the data will be uploaded to the power supply company's backend system to ensure that the user account matches the electricity meter data.

If abnormal data is found (such as the meter showing recharged but not recorded by the system), the system will trigger a manual verification process.

5、 Security and Compliance Assurance

encrypted communication

The data transmission between the electricity meter and the power supply system adopts encryption protocols (such as AES, RSA) to prevent hackers from tampering with the balance or sending false trip instructions.

Mandatory standard compliance

Smart meters need to be certified by national metrology departments (such as China CCC certification and EU MID certification) to ensure that the tripping logic and measurement accuracy meet standards (such as error ≤± 1%).

User permission management

Only the power supply company or authorized personnel can remotely control the meter tripping through the backend system, and users cannot modify the tripping threshold or force the power to be restored on their own.

The physical tripping mechanism of the electric meter needs to have anti pry design to avoid illegal closing.