In order to understand how to set up a G3 PLC network, and how it differentiates from PLAN PLC installations, one should know how the network set up with the current PLAN technology takes place.
PLAN (IEC 62056-61)
With a PLAN PLC, the data concentrator (DC) initialises every communication in the network and all communication takes place between the DC and device. When the DC is turned off there is no communication. The unique device identification is the system title that consists of the serial number and a supplier ID. Every device repeats each message as many times as the DC commands, and every device can join a PLAN network, even if not desired by the operator.
In a PLAN PLC network, there is one DC per one transformer station. In case of a cross talk situation, where a DC in a transformer station “sees” another DC, there may be issues as the devices recognize both DCs.
G3 (ITU G.9903)
With a G3 PLC, the DC acts as the PAN coordinator. New devices actively search for a PAN coordinator by sending so-called beacon requests. MAC address serves as the unique device identification, as derived from the Ethernet. Based on a pre-defined key, the DC (or the connected system) decides if a device is allowed to join the network. Only then a device can become an active device in the network. It is possible to have more than one DC’s per transformer station and to build up two or more logically separated networks under a single transformer station.
Communication in the G3 network follows the routing principle whereby messages are only repeated by devices that are part of the route between sender and destination. Each device in the network can communicate with any other device in the network or even devices outside of the G3 network, utilizing Ipv6 addressing. Multiple messages at the same time can be sent around different parts of the network. To prevent collisions, every device follows a strict “listen before talk” mechanism.
To make it happen
Before deploying a G3 PLC network, it’s important to make sure that all devices have a pre-shared key and corresponding tuple of MAC addresses so that the system can identify them. A unique ID is needed also for DC’s (or Gateways) for network identification and for addressing from outside of the network via IPv6.
The rollout of G3 devices usually starts from ‘inside out’ – meters closest to DC’s first - in order to have the required device density quite from the beginning. Mass installations are usually carried out in two phases: during the first phase, the meters are installed with no specific focus on communications performance. Typically, 98% of meters communicate as planned after this first phase. The target of the second step is to increase the communications rate to 100%, and this clean up work requires specific expertise and tools that show the neighbour topology information with related signal and noise level over a frequency range.Because of its OFDM modulation characteristics combined with advanced forward error correction, the G3 is exceptionally reliable in real world scenarios. This minimizes the clean-up and maintenance effort.
I would be happy to get your comments and/or experiences on PLC installations.
