What is a Smart Meter? Introduction to the Working Principle of Smart Meters

Smart meters are one of the basic devices for data collection of smart grids (especially smart distribution networks). They undertake the tasks of raw energy data collection, measurement and transmission, and are the basis for information integration, analysis and optimization, and information presentation. In addition to the basic power consumption measurement function of traditional electric energy meters, smart meters also have two-way multi-rate metering functions, user-side control functions, and two-way data communication with multiple data transmission modes in order to adapt to the use of smart grids and new energy. Function, anti-theft function and other intelligent functions.

The advanced measurement system and automatic meter reading system built on the basis of smart meters can provide users with more detailed electricity consumption information, so that users can better manage their electricity consumption, so as to save electricity bills and reduce greenhouse gas emissions. Goals: electricity retailers can flexibly formulate time-of-use electricity prices according to user needs, and promote the reform of the electricity market price system; power distribution companies can detect faults more quickly, and respond in a timely manner to strengthen power network control and management.

1. Concept definition of smart meter

The concept of smart meters has been around since the 1990s. When the static meter first appeared in 1993, its price was 10 to 20 times that of the electromechanical meter, so it was mainly used in large users. Later, as the number of electricity meters with remote communication capabilities increased, it was urgent to develop new systems for meter reading and data management. In such systems, metering data is beginning to be opened up to systems such as distribution automation, but these systems are not yet capable of effectively utilizing the relevant data. Likewise, real-time energy consumption data from prepayment meters is rarely used for applications such as energy management or energy-saving measures.

With the advancement of technology, mass-produced static meters can obtain powerful data processing and storage capabilities at a very low cost, which has greatly improved the intelligence level of small consumer meters, and static meters have gradually replaced traditional electromechanical meters. electric meter.

For the understanding of "smart meter", there is no unified concept and no unified international standard in the world. Europe usually adopts the concept of "smart meter", while "smart electric meter" refers specifically to smart meters; the United States is accustomed to adopting the concept of "advanced meter", but the essence is the same. Although "smart meter" is translated as a smart meter or a smart meter, it mainly refers to a smart meter. Different organizations, research institutes and enterprises in the world have given different definitions of "smart meter" in combination with corresponding functional requirements.

1.1 ESMA

The European Smart Metering Alliance (ESMA) defines a smart meter by describing its characteristics:

1.1.1 Automatic processing, transmission, management and use of metering data;

1.1.2 Automatic management of electric meters;

1.1.3 Two-way communication between meters;

1.1.4 Provide timely and valuable energy consumption information to relevant actors within the smart metering system, including energy consumers;

1.1.5 Services that support the improvement of energy utilization efficiency and energy management systems (generation, transmission, distribution, and consumption).

1.2 South Africa Eskom Power Company

Compared with traditional meters, smart meters can provide more consumption information, and can transmit this information to the local server through a specific network at any time, so as to achieve the purpose of metering and billing management. Also includes:

1.2.1 Integrates a variety of advanced technologies;

1.2.2 Real-time or quasi-real-time meter reading;

1.2.3 Detailed load characteristics;

1.2.4 Power outage records;

1.2.5 Power quality monitoring.

1.3 DRAM

Demand Response and Advanced Metering Coalition (DRAM) believes that smart meters should be able to achieve the following functions:

1.3.1 Measure energy usage data in different time periods, including hourly or time periods established by authoritative departments;

1.3.2 Allow power consumers, power companies and service organizations to conduct electricity transactions in various forms of electricity prices;

1.3.3 Provide other data and functions to improve the quality of electric service and solve problems in service.

1.4 Domestic

The smart instrument defined in China is an instrument with a microprocessor as the core, which can store measurement information and can analyze, synthesize and make various judgments on the measurement results in real time. It generally has automatic measurement functions, powerful data processing capabilities, automatic zero adjustment and unit conversion functions, simple fault prompts, human-computer interaction functions, operation panels and displays, and certain artificial intelligence. Usually, the electronic multi-functional energy meter using a microprocessor is defined as a smart meter, and features such as communication functions (carrier, GPRS, ZigBee, etc.), multi-user metering, and specific user (such as electric locomotive) metering are introduced into the smart meter. concept.

Combining various definitions, it can be considered that a smart meter is an intelligent instrument with the core of microprocessor application and network communication technology. / Local communication, real-time data interaction, multiple electricity price billing, remote power supply interruption, power quality monitoring, reading of water and gas heat meters, interaction with users and other functions. The smart metering system built on the basis of smart meters can support the requirements of the smart grid for load management, distributed power access, energy efficiency, grid scheduling, power market transactions, and emission reduction.

2. How smart meters work

A smart meter is an advanced metering device that collects, analyzes and manages electric energy information data based on modern communication technology, computer technology, and measurement technology. The basic principle of the smart meter is: relying on the A/D converter or the metering chip to collect the user's current and voltage in real time, and analyze and process it through the CPU to realize the calculation of forward and reverse, peak and valley or four-quadrant electric energy, and further calculate the power and other content Output via communication, display, etc.

The composition and working principle of electronic smart meters are very different from traditional inductive meters.

Inductive meters are mainly composed of aluminum discs, current and voltage coils, permanent magnets and other components. The electronic smart meter is mainly composed of electronic components. Its working principle is to first sample the user's power supply voltage and current in real time, and then use a dedicated electric energy meter integrated circuit to process the sampled voltage and current signals and convert them into The pulse output proportional to the electric energy is finally processed and controlled by the single-chip microcomputer to display the pulse as power consumption and output it.

Usually we call the number of pulses sent by the A/D converter when the smart meter measures one kilowatt-hour of electricity as the pulse constant. For smart meters, this is a relatively important constant because the A/D converter The number of pulses sent will directly determine the measurement accuracy of the meter.

3. Classification of smart meters

Smart watt-hour meters can be roughly divided into two categories: electromechanical and all-electronic in structure.

3.1 Mechatronics

Electromechanical integration, that is, adding certain parts to the original mechanical watt-hour meter so that it can not only complete the required functions, but also reduce the cost and be easy to install. On the basis of changing the national measurement standard, the sensor device is installed to become a smart meter with electrical pulse output at the same time as the mechanical measurement, so that the electronic counting and mechanical counting are synchronized, and its measurement accuracy is generally not lower than that of the mechanical counting meter. Degree meter. This design scheme adopts the mature technology of the original induction watch, and is mostly used for the transformation of old watches.

3.2 Fully electronic

The all-electronic type adopts electronic devices with integrated circuits as the core from measurement to data processing, thus canceling the long-term use of mechanical parts on the meter. Compared with the electromechanical integrated meter, the meter is smaller in size, more reliable, and more accurate. , The power consumption is reduced, and the production process is greatly improved. It does not have to be produced in a professional meter factory in the original sense, and will eventually replace the meter with mechanical parts.

4. Functional characteristics of smart meters

4.1 Reliability

The accuracy remains unchanged for a long time, no need for rotation calibration, no installation and transportation effects, etc.

4.2 Accuracy

Wide range, wide power factor, sensitive start, etc.

4.3 Function

Functions such as centralized meter reading, multi-tariff, prepayment, electricity theft prevention, and Internet access service requirements can be implemented.

4.4 Cost performance

High performance-to-price ratio, reserved expansion functions, less affected by price increases of raw materials, etc.

4.5 Alarm reminder When the remaining power is less than the alarm power, the meter will always display the remaining power to remind the user to purchase electricity; Buy electricity in time.

4.6 Data protection

Data protection adopts all-solid-state integrated circuit technology, and the data can be kept for more than 10 years after power failure.

4.7 Automatic power off

When the remaining power in the energy meter is zero, the energy meter will automatically trip and interrupt the power supply. At this time, the user should purchase electricity in time.

4.8 Write back function

The energy card can write back the user's accumulated power consumption, remaining power, and zero-crossing power to the electricity sales system to facilitate statistical management by the management department.

4.9 User sampling function

The power sales software can provide data for random inspection of electricity consumption and provide a user sequence for priority random inspection upon request.

4.10 Battery Query

Insert the IC card to display the total power purchase, the number of power purchases, the last power purchase, the accumulated power consumption, and the remaining power in sequence.

4.11 Overvoltage Protection

When the actual power load exceeds the set value, the meter will automatically cut off the power, insert the user card, and restore the power supply.

5. Main applications of smart meters

5.1 Billing and accounting

Accurate and real-time fee settlement information processing can be realized through smart meters, which simplifies the complicated process of accounting processing in the past. In the electricity market environment, dispatchers can switch energy retailers more timely and conveniently, and even fully automatic switching can be achieved in the future. At the same time, users can also obtain more accurate and timely energy consumption information and accounting information.

5.2 Distribution Network State Estimation

The power flow distribution information on the distribution network side is inaccurate, mainly because the information is comprehensively processed based on the network model, load estimates, and measurement information on the high-voltage side of the substation. By adding measurement nodes on the user side, more accurate load and network loss information will be obtained, thereby avoiding overload of power equipment and deterioration of power quality. By integrating a large amount of measurement data, the prediction of the unknown state and the verification of the accuracy of the measurement data can be realized.

5.3 Power quality and power supply reliability monitoring

The use of smart meters can monitor the power quality and power supply status in real time, so as to respond to user complaints in a timely and accurate manner, and take measures in advance to prevent the occurrence of power quality problems. There are gaps in the real-time and effectiveness of the traditional power quality analysis methods.

5.4 Load analysis, modeling and forecasting

Water, gas, and heat energy consumption data collected by smart meters can be used for load analysis and forecasting. By comprehensively analyzing the above information, load characteristics, and time changes, the total energy consumption and peak demand can be estimated and predicted. This information will provide convenience to users, energy retailers and distribution network dispatchers, promote rational electricity consumption, energy saving and consumption reduction, and optimize power grid planning and dispatching.

5.5 Power Demand Side Response

Demand-side response means controlling user load and distributed generation through electricity prices. It includes price control and load direct control. Price control generally includes time-of-use electricity prices, real-time electricity prices, and emergency peak electricity prices to meet the needs of regular electricity, short-term electricity, and peak electricity consumption, respectively. In direct load control, the network dispatcher usually realizes the connection and disconnection of loads through remote commands according to network conditions.

5.6 Energy Efficiency Monitoring and Management

By feeding back the energy consumption information provided by the smart meter to the user, the user can be prompted to reduce energy consumption or change the way of energy utilization. For families equipped with distributed power generation equipment, it can also provide users with reasonable power generation and power consumption schemes to maximize the benefits of users.

5.7 User energy management

Through the information provided by the smart meter, a user energy management system can be built on it, so as to provide energy management services for different users (residential users, commercial users, industrial users, etc.), and meet the indoor environment control (temperature, humidity, lighting, etc. ) while reducing energy consumption as much as possible to achieve the goal of reducing emissions.

5.8 Energy saving

Provide users with real-time energy consumption data, promote users to adjust their electricity consumption habits, and detect abnormal energy consumption caused by equipment failures in a timely manner. Based on the technology provided by smart meters, power companies, equipment suppliers and other market participants can provide users with new products and services, such as different types of time-of-use network electricity prices, electricity contracts with repurchase, spot price electricity contract etc.

5.9 Smart Home

Smart home refers to the connection of different devices, machines and other energy-consuming equipment in the home in a network, and controls according to the needs and behavior of residents, outdoor temperature and other parameters. It can realize the interconnection of heating, alarm, lighting, ventilation and other systems, so as to realize the remote control of home automation and home appliances and other equipment.

5.10 Preventive maintenance and failure analysis

The measurement function of smart meters helps to realize the preventive maintenance of distribution network components, energy meters, and user equipment, such as detecting voltage waveform distortion, harmonics, and imbalances caused by power electronic equipment failures and ground faults. The measurement data can also help the grid and users analyze grid component failures and network losses.

5.11 Prepaid

Compared with the traditional prepayment method, the smart meter can provide a lower cost, more flexible and friendly prepayment method.

5.12 Meter Management

Meter management includes: asset management of installed meters; maintenance of meter information database; regular access to meters; ensuring the normal installation and operation of meters; confirming the location of meter storage and correctness of user information, etc.

5.13 Load remote control

The overall connection and disconnection of the load can be realized through the smart meter, and some users can also be controlled, so as to cooperate with the dispatching department to realize power control; at the same time, the user can also realize the remote control of the specific load through the controllable switch.

5.14 Detection of illegal electricity use

The smart meter can detect events such as the opening of the meter box, the change of the wiring, and the update of the meter software, so as to detect electricity theft in time. For areas with a high incidence of electricity theft, potential electricity theft can also be detected in time by comparing the data of the master meter with the data of all the meters below it.

5.15 Others

Smart meters can provide users with value-added services such as grid faults, power outages, power quality, energy consumption, energy efficiency information, and recommended power consumption schemes, which improves the competition and efficiency of the energy market, and provides a solution for applications such as frequency, voltage, and reactive power control. Technical conditions.

6. Benefits of smart meters

6.1 Benefits for energy users

Smart meters can provide users with more accurate and timely accounting information; use accurate electricity records to enable users to better participate in the electricity market and benefit from flexible electricity demand; feedback on user energy consumption information and Energy automation systems; enhanced personal and equipment safety through better power quality and fault management, etc.

6.2 Revenues of power companies

The smart metering system based on smart meters can provide simple and efficient solutions for commercial applications such as metering, settlement, user service, state estimation, fault management, and power quality. Benefit from power quality, power flow and fault monitoring, and load management of the distribution network. The system can detect and solve existing problems in time, improve the efficiency of power outage management and user services, avoid damage to low-voltage distribution transformers caused by temporary overload, and provide energy consumption data for EMS and other systems.

6.3 Benefits of electricity market

The use of controllable distributed energy will provide new retail products for the electricity market, increasing the flexibility of rapid changes in market prices, thereby enhancing the competitiveness of the electricity market and the reliability of functional applications. Reduced market risk for electricity suppliers due to improved responsiveness to price peaks and reduction of extremely high price peaks. Data mining technology based on databases such as smart metering data and user data can help electricity retailers better understand customer needs and provide more targeted products. Improved load predictability further reduces costs and risks for retailers.

6.4 Social and Environmental Benefits

Smart metering systems have the potential to increase the energy efficiency of energy suppliers and end users. Timely and accurate energy consumption data feedback will enable users, home automation systems and suppliers to react quickly and focus on the most efficient measures. In addition to the direct energy-saving effect, the access of a large number of small and controllable energy sources has also promoted the promotion of efficient power generation methods such as renewable energy and combined heat and power generation.

6.5 Benefits of water, steam, heat and other applications

Smart meters can provide power supply for communication of water, steam, heat and other meters, and share remote communication channels to reduce communication costs. Aggregating measurement data from various energy forms can also help analyze and improve overall energy efficiency.