Do smart meters require an external power cord?

Smart metering meters usually do not require external independent power lines. Their power supply design fully considers reliability, safety, and cost, and mainly supplies power through the following two methods, depending on the application scenario and meter type:

1、 Built in power module: draws power directly from the grid (mainstream solution)

working principle

Smart meters directly draw electricity from the user's power supply line through a built-in power conversion module. For example:

Single phase electric meter: It obtains 220V AC power between the live wire (L) and the neutral wire (N), rectifies, filters, and stabilizes it, and outputs DC power (such as 5V, 12V) to supply power to the internal circuit of the electric meter.

Three phase electricity meter: Choose one phase or a combination from the three-phase lines (A, B, C) to obtain electricity, similar to the principle of single-phase electricity meter.

advantage

No need for additional wiring: directly using the existing power grid for power supply, easy installation, and low cost.

High reliability: As long as the power grid is supplying power normally, the electricity meter can continue to operate. In the event of a power outage (such as a user tripping due to overdue fees), only the measurement will be stopped, but the internal clock and stored data are usually maintained by backup batteries.

Easy maintenance: The power module and electricity meter are designed to be integrated, with a low failure rate and a lifespan synchronized with the electricity meter (up to 10 years or more).

Applicable scenarios

Suitable for the vast majority of residential, commercial, and industrial electricity usage scenarios, especially in areas with well-developed power grid coverage.

2、 Backup power supply: Battery powered (supplementary for special scenarios)

Battery function

When the power grid is cut off, the backup battery provides critical functional support for the electricity meter, including:

Maintain clock: Ensure accurate time recording during power outages to avoid measurement data confusion.

Save data: prevent power outages from causing loss of stored data such as electricity consumption and event records.

Support trip logic: Ensure reliable transmission of relay action signals in case of overdue tripping.

Battery Type

Lithium manganese batteries, such as CR123A and ER14250, have a lifespan of 5-10 years and are suitable for low-temperature environments.

Lithium ion batteries: rechargeable, with a lifespan of 3-5 years, requiring a charging circuit and high cost.

Capacitive energy storage: Some meters use supercapacitors as short-term backup power sources, which have a long lifespan but small capacity.

Applicable scenarios

In areas with unstable power grids, such as remote mountainous areas and frequent power outages, batteries can extend the storage time of electricity meter data.

Critical load measurement: In scenarios such as hospitals and data centers that are sensitive to power outages, it is necessary to ensure measurement continuity.

Prepaid electricity meter: After the overdue payment trips, the battery maintains the status display and remote communication function of the electricity meter.

3、 Special scenario: necessity of external power cord

Although the vast majority of smart meters do not require an external power cord, it may be necessary in the following special circumstances:

Areas without power grid coverage

Solar/wind power supply system: In off grid scenarios (such as remote villages and communication base stations), the electricity meter needs to be connected to the DC power output from the solar controller or wind turbine through an external power line (such as 12V, 24V), and then powered by internal DC-DC conversion.

Diesel generator power supply: In temporary electricity scenarios, the electricity meter may draw power from the output terminal of the generator.

Scenarios with high security requirements

Explosion proof environment: For example, in chemical plants and gas stations, the electric meter needs to adopt an inherently safe design, and the power cord may need to be independently wired to avoid the risk of electric sparks.

Areas with severe electromagnetic interference: such as near high-voltage substations, electricity meters may reduce interference by shielding power lines.

Multi functional integrated electric meter

Some smart meters integrate communication modules (such as 4G, 5G) and sensors (such as temperature and humidity), with high power consumption, and may require external low-voltage DC power supply (such as POE power supply) to enhance stability.

4、 Key considerations in power supply design

Wide voltage range adaptation

The smart meter power module usually supports 85V-265V AC input, compatible with global grid voltage fluctuations, and avoids damage caused by unstable voltage.

low-power design

Adopting efficient switching power supply technology, with a typical power consumption of ≤ 5W (single-phase meter), to reduce the impact of self energy consumption on measurement accuracy.

Safety Certification

The power supply part needs to be certified according to standards such as IEC 62052-11 and GB/T 17215 to ensure that insulation, voltage resistance, and fire resistance meet the standards.

fault protection

Built in overvoltage, overcurrent, and short-circuit protection circuits to prevent power failures from causing fires or meter damage.

5、 Frequently Asked Questions and Answers for Users

Q: Will data be lost after the electricity meter loses power?

A: I won't. The backup battery can maintain data storage and clock operation for several years (depending on battery capacity), and the data will automatically synchronize after the power grid is restored.

Q: Do batteries need to be replaced regularly?

A: Lithium manganese batteries have a longer lifespan (5-10 years), usually equivalent to the lifespan of an electric meter; Lithium ion batteries need to be charged or replaced regularly according to the instructions.

Q: Will the external power cord affect the measurement accuracy?

A: I won't. The power cord and metering circuit are designed independently and have passed electromagnetic compatibility (EMC) testing to ensure no interference.