Editorial by Txetxu Arzuaga, ZIV Metering BU Development Manager
Telecommunication networks is one of the most important factor for assuring a successful Advanced Metering Infrastructure. The choice of the appropriate technology is not an easy decision for electricity distribution companies. Several questions arise. For example, should distribution companies rely their AMI deployments on private telecommunication networks our should they pay for the telecommunication services that public network carriers start to tailor for them? Even more important to that, is this telecommunication network only for transporting the data generated by the smart electricity meters or should they think in a more generic telecommunication network that is deployed to convey additional services, such as telecontrol or automation data to be generated by a new generation of smart devices to be installed along the medium voltage (MV) and low voltage (LV) grid?
Many Utilities have decided their deployments should rely on private networks in different grid segments. Powerline technologies such as PRIME (http://www.prime-alliance.org) are very good examples on how a multiservice telecommunication network can be deployed along the low voltage grid (the last mile) to provide data services for any smart device, such as the smart meters, that are plugged to the LV grid. For instance, there are many urban and underground distribution grids around the globe, where large MV/LV transformers (300kVA to 500kVA) may have to well over 8 LV feeders serving several hundreds of customers connected along the LV feeders and LV branches. PRIME telecommunication networks show very good performance, in terms of throughput and availability, in such a grid topology. The same is also true in rural distribution grids, that also benefit from the PRIME technology. In this case, MV/LV transformers are smaller (50kVA) and normally pole mounted, being the LV distribution grid overhead.
PRIME is one of the best baseline technologies for deploying telecommunication networks for LV grids, but the deployment of a private telecommunication network for smart grid services should also look at the MV grid segment. In the case of MV grids, many urban installations across the world are underground looped networks (providing added system reliability) and rural installations are overhead non-looped networks. In all cases, each MV secondary substation hosts an independent PRIME subnetwork that provides data services to all smart devices plugged to the LV grid, but in many cases just from the substation to the smart meters. The challenge is to connect all above PRIME subnetworks to the backbone. For high density urban MV grids, either fiber optics or MV powerline communications can provide the requested high throughput (over 10 Mbps).
In the case of rural MV grids, where a pole mounted small MV/LV transformer feeds a reduced number of customers (<50), wireless medium range (5 – 10 km) private networks can support architectures where PRIME, as a decision of the utility, is not going to be used in MV communications. These wireless technologies, based on standard protocols such as IEEE 802.15.4g (using the available frequency bands 868 MHz (EU), 915 MHz (USA), 2.4 GHz ISM bands (worldwide)) and RPL (IPv6 Routing Protocol for Low-Power and Lossy Networks) can be an interesting technology to create a RF mesh networks that interconnect, or connect, all the PRIME subnetworks to the backbone.
The baseline technology that will assure the interoperability between PRIME subnetworks, in the LV grid, and RF mesh networks in the MV grid is the IPv6 protocol. PRIME IPv6 convergence layer provides an efficient method for transferring IPv6 packets over the PRIME network. By default, the PRIME Base Node, that manages the LV telecommunication network, will act as a IPv6 router between the PRIME subnetwork and the RF mesh network. Real hybrid RF and PLC networks will be possible thanks to PRIME IPv6 routers.