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A primer on power line communication

Posted: 02 Jan 2012     Print Version  Bookmark and Share

Keywords:Power line communication  cables  Narrowband  Broadband 

Talking about applications, PLC has made Load Control a reality in many EU Countries. Home appliances like washing machine, dryer, dishwasher, oven and stove, refrigerator, freezer, air conditioner and water heater, talk to the Smart Meter, (Refer to previous section for details) which gathers information of peak pricing hours from the utility through PLC. The appliances can then switch OFF/ON according to the price variations. This is a win-win situation for the consumer who saves on the electricity bill, and the utility, which can better manage peak demands. PLC also enables appliance monitoring and HVAC control – leading to further energy awareness and savings.

Home automation potentially focuses on the following applications:

 • Lighting
 • Appliance/Device Diagnostics and Monitoring
 • Security Access
 • AMI
 • Home health monitoring

In a sample home area network, the sensors on the appliance side are connected to the Monitor via the Power Line. Any changes on the appliance end will be reflected on the LCD Display, which can be viewed and changed as required. Consumers will literally have control of their entire house at their fingertips.

PLC is a considerably more effective in home networks. HAN being realised by Wireless/Zigbee, will need new infrastructure to be installed. Moreover, penetrating physical barriers like walls within one floor, or reaching out to different floors is a challenge for Wireless. Wireless networks often face performance issues, like mentioned in the previous section, due to RF interference caused by devices like microwave oven, cordless phones or even Bluetooth devices at home. PLC on the other hand can reach out to every node connected via the power line. It converts virtually every socket in one?s home into an access point, in many ways incorporating the best of wired and wireless communication.

Vehicle-to-grid communication
Plug in electric vehicles (BEVs and PHEVs) communicate with the power grid, both, to charge itself and to deliver electricity into the grid. Different versions of V2G would include a Fuel-cell vehicle, a battery powered vehicle or a solar vehicle. In all cases, the vehicle provides power to the grid at peak load conditions and charges itself at night, when the demand is low. A variety of data like vehicle identification, current battery status, maximum allowed charge current and number of phases, charging times (e.g. delayed charging start) and overall 'charged' electricity amount with associated costs is needs to be exchanged with the EVSE (Electric Vehicle Supply Equipment).

PLC has a distinct advantage here because an unambiguous physical association between the vehicle and a specific EVSE can be established—this aids in authentication and security. This is clearly something that is not possible to accomplish with wireless solutions even if short range. PLC further connects the EVSE to the meter ('re' for unit of measurement) and the smart grid. This technology is still in its infancy with no existing standards but promises to be an exciting trend to watch out for in the next decade.

Other applications
In order to give readers a glimpse of the enormous potential of PLC in the energy consumption market, 2 applications will be dealt with in detail. PLC in data centre power distribution networks, and PLC in Lighting.

Smart power in data centres
The problem: With the rise of cloud computing and internet services, data centres and collocation facilities continue to show consistent double digit growth. Data centre downtime is completely unacceptable due to loss of revenue and reputation that it causes. Such downtime is primarily caused by UPS battery failure, UPS overloading, and circuit breaker failure. Another critical concern for data centres is energy efficiency of devices because of rising unit electricity costs and additional cooling costs. Simultaneously, companies who outsource their computing requirements want access to all performance metrics of their systems including power at various levels. Adding communication between devices is a challenge, because wireless cannot work reliably in the data centre environment while wired communication would exacerbate the problem of cable clutter.

Consider traditional power distribution architecture in a data centre – a highly simplified diagram is shown in figure 2 for the purpose of understanding.

Figure 2: Power distribution topology in a typical data centre.

AC supply from the grid first flows through the Uninterruptible Power Supply (UPS), then the Power Distribution Unit (PDU), then converted to DC power at the Power Supply Unit (PSU) and then finally to a Server, Switch, Network storage device or in general, a network device. In such configurations with redundant power provisioning, UPS load rarely exceeds 30% of its rated capacity. This is largely because the power topology down-stream from a UPS is not clearly visible at the UPS – it is difficult to trace which/how many Network Devices are connected to that UPS.

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