Posted on 24 July 2019
For communication between the meter and the upper level systems HES / MDMS, various wired and wireless technologies are used, the most popular are: PLC, RF, 3GPP. The continuous development of technologies for smart metering of electricity and the requirements for the volume of transmitted data and the frequency of their collection makes the choice of the necessary technology rather difficult.
In North America, wireless communications technology is the most common, while power lines (PLC) dominate Europe and the Asia-Pacific region. The third alternative is cellular networks (3GPP), which were used for some full-scale projects.
If we consider some EU countries, the distribution of key communication interfaces used in smart energy metering systems is as follows: Austria -70% PLC, 30% 3GPP, Czech Republic - 99% PLC, 1% 3GPP; Estonia - 90% PLC, 10% 3GPP; Finland - 30% PLC, 60% 3GPP; 10% RF; in France, Italy, Spain, Latvia, Poland, the dominant technology is PLC.
PLC is a very powerful and functional system for communication between the data concentrator and the meter. But like any system, PLC has both advantages and disadvantages.
• Ease of use.
• Low installation and operating costs. It does not require laying a separate cable, if there is a power line, then there is also a communication channel with the meter.
• Registration of equipment as radio frequency is not required.
• Provides a mechanism to suppress the signal in a given range.
• Sensitivity to interference generated by low-quality consumer equipment.
RF is a flexible and convenient radio system designed to transmit data from meters that are difficult to access. Information is collected from the meters due to the wireless data transfer technology RF-mesh, which allows you to receive and transmit data on energy consumption.
• Reduced operating and maintenance costs.
• No wired lines from metering devices to data collection equipment.
• Reading data from devices installed in hard to reach places.
• The minimum number of settings, but, nevertheless, can be flexibly adapted to a wide range of tasks.
Disadvantages of RF-mesh:
• Limited frequency resource.
• Organization of placement of access points in the maximum proximity to subscribers.
• Providing round-the-clock power supply.
To get the best coverage and combine the advantages of PLC and RF technologies, ADD GRUP offers a hybrid solution based on the new STMicroelectronics development. This solution allows you to improve data collection and make it more reliable. If one of the systems fails for any reason, an automatic switch to the other will occur. In addition, the hybrid solution can be used in more countries, as each country has different requirements for power grids.
ADDAX Hybrid (PLC+RF) solution is based on open standards and provides for seamless integration into ADDAX AMI. The protocol stack is presented below:
5. Application Layer
4. Transport Layer
3. Network Layer
2. Data Link Layer
G3-PLC + RF 6LoWPAN
G3-PLC + RF MAC
1. Physical Layer
G3-PLC + RF PHY
The lower layers are based on G3-PLC specification. The G3-PLC data link layer is adapted for hybrid network.
The physical layer for PLC supports CENELEC A and FCC frequency bands. The band to be used as well as tone mask can be configured as required.
The physical layer for RF supports a large set of bands – from 430 to 1000 MHz. This covers all popular license-free bands for worldwide markets: 433 MHz, 868 MHz and 915 MHz.
The main goal of the 6LoWPAN adaptation layer is to optimize the transmission of IPv6 packets over low-power and noisy networks.
The IPv6 layer provides for devices addressing, while UDP is used as a lightweight transport protocol.
The top layer in the communication profile is DLMS/COSEM application layer. It provides services to establish a logical connection between the client and the server(s). It also provides the xDLMS messaging services to access attributes and methods of the COSEM interface objects.
Every meter has PLC or RF, or PLC+RF connectivity to other meters. The route is built hop-to-hop, selecting between the best channel. The channel selection is dynamically adjusted based on media status. This provides for better meters availability in any conditions.
Security features are implemented at several layers. AES-128 based encryption and authentication, defined in G3-PLC specification, is used at data link layer. At application layer the security architecture is based on the DLMS concepts. AES-GCM-128 (Galois/Counter Mode with AES-128) Security Suite ID: 0 is implemented for data encryption and authentication, and key transport methods.
An add-on to the last mile communications for AMI system, the solution features a RF-based consumer interface. This interface doesn’t require any additional hardware on meter side. A point-to-point communication between the meter and Customer Interface Unit is used. This feature is used for enabling the consumer to read the actual data from pole mounted meters.
Advantages of a hybrid solution
Since large utilities serve different territories, including hard-to-reach and interference areas, it became necessary to create a hybrid solution that would include a combination of PLC and RF systems. Joining 2 systems in one solution gives many advantages, including:
• Improving the reliability of data collection.
• High interference immunity.
• Reducing the cost of operation and maintenance of equipment.
• High speed data transfer.
• High security.
Combining all the advantages of PLC and RF systems into one system makes the hybrid solution from ADD GRUP the optimal choice for many purposes. Such a system can help improve the performance, reliability, capacity and scalability of the network, which leads to additional savings during system exploitation.