Sumitomo Electric Develops PLC String Monitoring Unit for 1,500 V DC Solar Power Plants

Sumitomo Electric Industries, Ltd. is now open for orders for a power line communication (PLC)*¹string monitoring unit it has developed for 1,500 V DC solar power plants. This monitoring unit is scheduled to begin shipping in July 2018 to solar power plants in Japan and abroad.

Under the feed-in tariff (FIT)*²for renewable energy, the price for generated electricity has recently been decreasing. Against this backdrop, an increasing number of solar power plant construction projects have been designed at 1,500 V DC to reduce the installation cost. Compared with the previously dominant 1,000 V DC designs, 1,500 V DC designs reduce component and member quantity required and promises a lower installation cost through the use of more panels per string.*³

In line with this trend, Sumitomo Electric has developed a PLC string monitoring unit compatible with 1,500 V DC, in addition to the previous product tailored for 1,000 V designs. This product monitors each string to determine whether the solar power plant is operating properly and detects faults. The slave units of the product monitor strings, while the master unit collects data, with the communication between them being based on Sumitomo Electric's superior PLC technology. Advantages of this configuration include: ① Use of an existing power line for communication eliminates the need for additional installation of a communication line, reducing the overall cost and ②The wired system ensures stable communications. Consequently, this product enables the construction of 1,500 V DC solar power plants equipped with monitoring functions at a more reasonable cost.

Additionally, Sumitomo Electric plans to make this product compliant with International Electrotechnical Commission (IEC) standards*⁴for use at solar power plants in IEC member countries.

Product Features

1. Compatible with 1,500 V DC power plants
2. Installable in various combiner boxes due to versatile design (two vertically stacked or separately installed boards)
3. Covers up to 20 strings and is suitable at sites with various string designs
4. Stable data communication due to PLC, which is specifically highly lightning resistant, and Sumitomo Electric's proprietary noise immunity design
5. Compliance with IEC standards planned for use in IEC member countries

*1 Power line communication (PLC): A technology designed to use a power line as a communication channel. Sumitomo Electric's PLC products use low-frequency PLC technology at frequencies not higher than 450 kHz. String current measurement data signals are added to a DC line.

*2 Feed-in tariff (FIT) for renewable energy: Under this scheme, the national government forces power companies to purchase electricity generated from renewable energy sources at a fixed price for a fixed period. The FIT commenced in July 2012.

*3 String: A minimum configuration unit of series-connected photovoltaic panels.

*4 International Electrotechnical Commission (IEC) standards: International standards in electric and electronic technology fields established by the International Electrotechnical Commission (IEC). There are 83 IEC member countries (as of April 2017).