Engineer:Olivia Chu Tel:+8618761501293 E-mail:olivia.chu@email.acrel.cn

Jiangsu Acrel Electrical MFG Co. Ltd

Abstract: This article expounds the main functions of the traditional IC card prepaid energy meter, analyzes its application advantages and disadvantages; introduces in detail the function expansion of prepaid energy meter after integrating communication technology ,intelligent control technology And promote the practical value, to describe the possible technical development trend of prepaid energy meter.

Keyword:Prepaid energy meter,application,analysis

Electricity charges are the main source of funds for power supply enterprises to maintain production and development, whether they can be charged in time plays an important role in the capital circulation of power supply enterprises. Due to the "use electricity first, pay later" electricity consumption model for many years, the wide-ranging electricity user base and the technical means of on-site power outage and power rationing, as well as the incompatibility of supporting regulations with the market economy, It directly leads to the huge risk of power supply enterprises in charging electricity charges, manpower, financial resources, and operational pressure have been poured into it over the years. In this context, in order to better adapt to the reform of the power system, prepaid electricity meters have been widely used.

Due to the immature application of the early core related communication technology, the compatibility of the system has become an important obstacle affecting the popularization and application of the remote automatic meter reading system for electric energy metering management, especially the compatibility of the communication protocol and the inconsistency of the manufacturing standard. Under the environment at that time, the IC card type prepaid energy meter had no choice but to avoid the application bottleneck of communication technology.

1.I Card Type Prepaid Energy Meter

1.1 Main function

1.1.1 Metering function: single phase metering active energy; save historical power, and has the function of power freezing.

1.1.2 Multi-tariff function: Programmable setting time period, multiple tariffs. The timing clock has a temperature compensation function.

1.1.3 Communication function: with RS485 interface and an infrared communication interface. The RS485 interface is generally electrically isolated from the inside of the meter and has an anti-AC 220V access protection design

1.1.4. Display function: LCD display, the button can automatically cycle display, the interface show such as the remaining amount, total power, current electricity price and so on.

1.1.5. Information copy-back power purchase function: one meter one card, that is, one meter can only correspond to one IC card. When the card is inserted for power transmission, the electricity consumption information in the meter is automatically copied back to the IC card; when electricity is purchased again, the information in the card is automatically written into the computer for archiving and data verification.

1.1.6. Meter recharging reminder function: Generally, there are display alarm and power failure alarm, also increase the function of cutting off the load .

1.1.7. Overload control function: By setting the power threshold, it can realize the power-off control of overload at load side. The power-off time can be set in two ways: immediate power-off and delayed power-off. The power can be restored by pressing the button or inserting the card.

1.1.8. Prepaid control function: the meter realizes the management method of purchasing electricity first and then using electricity. When there is no electricity charge in the meter, the load switch in the meter will automatically cut off the load power supply. After charging the meter, the meter will re-close to restore the load power supply function. With the continuous improvement, the overdraft function has been added, which can allow moderate overdraft according to the actual situation. The overdraft can be set. After the overdraft is completed, the meter will be powered off, and the overdraft part will be automatically charged and subtracted when the meter is recharged next time.

1.1.9. Anti-hoarding power function: Due to the macro-control of the electricity price policy, in order to prevent excessive power (amount) from being charged into the meter, the customer is restricted from charging too much power (amount) at one time by setting the hoarding power threshold in the meter.

10. Security protection function: Generally, CPU card technology is used for system security design. The security authentication of the CPU card electric energy meter and the CPU card is completed through the ESAM module in the energy meter. The MCU of the CPU card energy meter only plays the role of data transmission during the authentication process, and does not participate in data encryption and decryption. When selling electricity, through a series of key authentication tests, operations such as the confirmation of the power purchase card, the permission to write information on the power purchase card, and the permission to write back the binary file erasure can be realized.

1.2 Main Advantage

1.2.1 Improve meter reading efficiency and accuracy. Through the RS485 interface and infrared communication interface, the corresponding handheld meter reading device can be used for on-site batch transcription. This has a very important effect on the current situation that the number of energy meters managed by power supply enterprises has increased sharply.

1.2.2 Effectively solve the problem of arrears. Significantly reduced operating costs for electricity bill collection, and Enhanced security of electricity fee collection

1.2.3 Alleviate the contradiction of payment difficulties. With the large increase in the number of customers and relatively concentrated payment time slots, the traditional charging model is very easy to cause payment congestion. The application of prepaid energy meters has greatly reduced the pressure on counter charges and service risks.

1.3 Problems in the application

1.3.1 Poor anti-attack ability. The loss and damage of the IC card, especially its open IC card read and write ports are vulnerable to external attacks. It is difficult to obtain evidence after being attacked and cause the failure of the internal control system, and it is very easy to have electricity disputes.

1.3.2 Management is difficult. Due to the suddenness and randomness of IC card power purchase, the power supply department has increased the pressure of selling power. At the same time, in order to ensure data security, smart CPU cards are widely used at present. Its COS system and dynamic key authentication ensure data security, but also increase the management workload of the power management department at the same time. Moreover, the multi-link demonstration increases the occurrence of unexpected failures.

1.3.3 The adaptability of electricity price policy adjustment is not strong. The electricity price has been determined and written into the prepaid energy meter when purchasing electricity. Since the electricity price stored in the IC card prepaid energy meter cannot be adjusted in real time, each price adjustment adds a lot of workload to the power supply company,Customers are also prone to question.

1.3.4 Data collection is not timely. It cannot reflect the customer's electricity consumption status in real time, cannot effectively monitor electricity theft, and cannot meet the real-time management needs of electricity management automation

1.3.5 The function scalability of the power purchase method is not high. The prepayment system using IC cards as the data transmission medium is not easy to form an effective linkage with telephone banking, online banking and other electricity purchase methods. Customers often purchase electricity at electricity sales outlets with cards, which reduces the service quality of electricity marketing and increases the workload of power supply companies. Therefore, in order to solve the problems and drawbacks in the actual application of IC card prepaid energy meters,The compatibility problem of the communication system is solved. The breakthrough of the bottleneck of the core related technology provides a vast space that may be unimaginable for the remote application of prepaid energy meters.

2 Integration of prepaid energy meter and remote meter reading system

2.1 The basic communication methods in the remote meter reading system mainly include optical fiber communication, telephone line communication, RS485 bus, TV cable, Internet, power line carrier communication, instrument bus, satellite communication, GPRS and CDMA, etc. All kinds of communication methods have their advantages and disadvantages and their applicable aspects. Combined with the industry characteristics of power supply enterprises and the practical application of low-voltage power line carrier spread spectrum, frequency hopping, forwarding and relaying (the carrier meter can be dynamically set as a router or transponder by the local concentrator through the power line) technology and special chips’ practical application .At present,the low-voltage of remote automatic meter reading The system mostly adopts the power line carrier centralized meter reading method + GPRS remote transmission + prepaid energy meter series of technical solutions .

2.2 System structure power line carrier centralized meter reading system is composed of centralized reading master stations, collectors, concentrators, meters and other equipment. According to the site conditions, a dedicated network is established, and the meter reading, control and management of electricity consumption are carried out through software. The system consists of three physical layers and two link layers. The data collection of the master station adopts a star structure, that is, one power consumption management center is the management layer to multiple concentrators; the master station is connected to the data concentrator through the GPRS network; The collectors are connected through low-voltage power lines, the collectors are installed in the meter box, and the collectors and customer energy meters are connected in parallel through the RS485 interface to form the customer layer.

2.3 System features

2.3.1 Adopt PLC (power line carrier) communication method: effective use of power grid topology structure, easy construction.

2.3.2 Basic data group: all customers included in the centralized copying system can be selected for copying (point copying, full copying), multi-point copying to form a basic data group, and various analyzes (line loss, multiple rate, load, etc.), To meet the needs of various intelligent management of customers.

2.3.3 Combination of software and hardware: The system design fully considers the needs and convenience of users. On the basis of fixed hardware, all system function compensation, management modification, and operation addition (remote control power) are all completed by the background software.

2.3.4 It has the advantages of convenient installation, high reliability, good safety and strong maintainability. At the same time, the project cost is low, the system maintenance is simple, and the operation cost is low.

2.4 Application of main functions

The remote prepayment energy meter cooperates with the power consumption management system to realize functions such as remote meter reading, remote prepayment, electricity theft prevention, and load management.

2.4.1 Remote meter reading

The master station can perform random meter reading, and judge whether the on-site energy meter is faulty or whether the customer's electricity consumption is abnormal according to the read-back data. The main station can also read the meter according to the meter reading routine, and transmit the read back data to the power marketing management information system for electricity cost calculation. At the same time, the master station can also make the electric energy meter regularly report the field data information through remote setting.

2.4.2 remote prepaid

Customers can purchase electricity in various forms to effectively avoid payment peaks. When the remaining amount in the customer's meter is 0, the meter outputs a trip signal to make the internal relay or the external load control switch act to cut off the power, avoiding the behavior of arrears. The remote prepayment method is safe and reliable, avoiding failures such as non-reading of the card and information errors due to the transmission of information through the IC card. At the same time, when the electricity price is adjusted, the electricity price parameters in the on-site energy meter can be modified in batches in a timely manner through the master station, so as to ensure that the electricity price parameters in the on-site energy meter are synchronized with the price adjustment.

2.4.3 Anti-stealing

When the parameters of the on-site electric energy meter change or there are failures such as loss of voltage, current loss, and wrong wiring, the electric energy meter can be automatically reported to the main station. Go to the site for an inspection. This function can effectively steal electricity and prevent problems before they happen.

2.4.4 load management

The master station can collect the voltage, current, power, electricity and other data of the on-site energy meter for load analysis and management. According to the current data, the load curve can be drawn to monitor the change of the electricity load. According to the voltage data, the voltage qualification rate can be calculated. By setting the active power limit in the energy meter, control the customer's overload power consumption.

2.5 gain analysis

2.5.1 Due to the use of remote meter reading, a large number of manpower costs for meter readers can be saved. At the same time, errors in manual meter reading can be avoided, and meter faults can be found in time, thereby improving service levels.

2.5.2 Due to the implementation of pre-payment, the arrears have been greatly reduced, the recovery rate of electricity charges has been improved, and the operating costs of on-site restoration of electricity in the recovery management of electricity charges have been reduced.

2.5.3 Since the on-line monitoring of the operation status of the on-site electric energy meter can be carried out, it can effectively prevent electricity theft and reduce the unknown loss of electricity.

2.5.4 Due to the automatic load control, the occurrence of overload meter burning is eliminated, at the same time, the phenomenon that customers do not perform time-of-use electricity price and power rate assessment due to underreporting power consumption capacity is avoided.

3. Acrel Prepaid products application scenario

3.1 Function

Prepaid meter electricity charge collection, control, arrears trip; provide post-payment management module; energy consumption analysis module;

Collection of rent and property fees, and arrears;

Shared electricity charges in public areas;

Access to meter reading and metering in public areas and substations;

Prepayment + building energy consumption, classified and sub-item energy measurement integrated system;

Centralized financial management and control of property/real estate groups, separate authority for sub-properties;

The wireless solution is easy to modify and easy to debug

4. Product Selection

5. Conclusion

Although many disadvantages of traditional prepaid energy meters are becoming more and more prominent that they cannot meet the needs of modern electricity management, in the short term, especially in regions where the customer base is relatively dispersed, there is still a certain degree of application. On the other hand, with the continuous development of society, prepaid energy meters will be more closely integrated with communication technology and intelligent control technology (for example, remote prepaid energy meters based on mobile communication technology may completely replace traditional IC card prepaid energy meters. scope of application of the energy meter). For prepaid energy meters, it is an inevitable technological development trend to have the function of "remote real-time intelligent control" in order to expand into a larger world. For power supply enterprises, the popularization and application of the "remote real-time intelligent control" function will also be able to continuously improve the management level and service quality of daily electricity consumption.

References:

[1] Acrel Enterprise Microgrid Design and Application Manual. Version 2022.05