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Newsletter "SEI NEWS" 2014

Home > Company Information > SEI WORLD > Back number > Vol.441

[Newsletter "SEI WORLD" Vol.441]

Power Line Communication (PLC)-Based Real-Time Mega-Solar Monitoring System

Initial installation defects, long-term degradation and malfunctions in solar panels cause decreases in generated or sold electricity. Since current mega-solar systems comprise tens of thousands to hundreds of thousands of panels, it is difficult to identify degraded panels from decreases in total generated electricity. Therefore, demand is high for an inexpensive monitoring system that can be installed easily and that accurately monitors each panel for generated electricity in real time.

As a solution to this situation, Sumitomo Electric has commercialized a mega-solar monitoring system, using the PLC technology that employs, as a communication medium, high-voltage DC power cables rated at 600 V to 1 kV or higher incorporated in mega-solar systems. For the commercialization of this system, Yurtec Corporation provided us with support and cooperation.

Under high DC voltage or heavy power noise conditions, the PLC technology had not yet been commercialized. However, the proprietary PLC technology developed by Sumitomo Electric and incorporated in the present monitoring system transmits information accurately without a hitch even in a heavy noise environment generated by high-capacity power conditioners used specifically with mega-solar systems.

■What is PLC?

Power line communication (PLC) technology uses existing power lines as communication lines, enabling data transmission without the need to install an additional communication line.

 
Example monitoring system configuration (500 kW system, 10 slave units)   PLC terminal installed in existing connection box

Feature 1: Requires no additional wiring for communication

The monitoring system places a PLC-based slave unit in a connection box. Current and solar voltage data measured on individual strings*1 are sent to the monitor unit via an existing power line. Consequently, no additional wiring is needed for communication purposes. Moreover, since power required to operate slave units is supplied from the solar power line, no mains cord is required.

Feature 2: Usable with existing mega-solar systems

The monitoring system is compatible with clamped current sensors as well as with the penetrating type. Sensors, slave units, and the master unit can be added to an existing system without the need to modify the existing mega-solar equipment.

Feature 3: Resists noise and lightning surges

Drawing on our years of experience in PLC technology, the monitoring system exhibits high communication performance against power supply noise and is fully protected from lightning surges.

Feature 4: Outperforms other systems in cost

Slave units 160 mm x 130 mm x 50 mm in size and 500 g in weight are small enough to be installed in a connection box, requiring no extra outdoor enclosure. The master unit can be further downsized, although depending on the installation location and method. It is possible to reduce installation costs since the monitoring system can be installed easily whether with an existing or newly-installed mega-solar system.

*1:String
A row of series-connected photovoltaic panels
*2:Lightning surge
Overvoltage and overcurrent generated by lightning strikes

 

Power System R&D Center

 
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