String Box SB 15-15 / SB 15-08
PART OF THE MONITORING SYSTEM FOR PHOTOVOLTAIC POWER PLANTS
A String Box SB 15-15or SB 15-08 is employed for paralleling of up to 15 strings of a photovoltaic array and measuring of the single string currents. Therefore, it has to be connected between the photovoltaic modules and the central inverter. The integrated microcontroller-based measuring card processes the measured current values and has one input for the common DC-voltage. The measuring data are provided over CANinterface or Ethernet-port.
One of the highlights of the String Box is the test function of the measuring card. When pressing the test button, a defined test current flows through all current sensors in order to to check their functionality. Another highlight is the zero-current detection. If all string currents are less than 2 % of the rated value, a LED signalises, that any fuse disconnector can be opened without the risk of arc flash.
The String Box is protected by fuses in the positive and negative current path of each string. A common surge arrester comprising class 1 and class 2 protections is also installed. The plastic housing complies with IP66 and is therefore also suitable for outdoor installation. The string box is available with a number of nn ≤ 15 inputs and in two current ratings: 15 A (SB nn-15) and 8 A (SB nn-08).
A whole Monitoring System consists at least of one
String Box SB 15-15 or SB 15-08 and the Helios
Systems analysis software “String Monitoring” on a
PC under Windows XP. Additional string boxes can
be integrated according to the customers needs.
Communication between String Boxes and PC is
either realised by Ethernet or by CAN-bus. The latter
requires an additional Helios Systems CAN-MUX
card but allows longer distances between the
components and is therefore adequate for large
photovoltaic power plants. CAN-MUX card,
industrial PC and peripherals, integrated in a
common housing called “Communication Cabinet”,
are also available as a turnkey solution from Helios
Systems.
The String Box is the elementary building block of the Helios Systems Monitoring System, because it allows a closer look on every single string current—essential for a detailed analysis of the performance of your photovoltaic power plant—without any compromise in safety!
Ordering information
The type number has the following format: SB nn-aa
‘nn’ defines the number of inputs (nn = 01...15)
‘aa’ defines the maximum PV string current (aa = 08 or 15):
Example: To get a String Box with 9 inputs and a rated current of 15 Amps, please order a SB 09-15.
TECHNIAL DATA OF THE STRING BOX SB 15-15 / SB 15-08
Electrical Data
| Maximum PV voltage | 1000 VDC | |
| Maximum number of strings | 15 | Individual lower number on request. |
| Maximum PV string current | 15 ADC / 8 ADC | SB 15-15 / SB 15-08 |
| Rated supply voltage | 18 -75 VDC | Typical 48 VDC |
| Rated supply power | 5 W | |
| Communication interface | CAN or Ethernet | |
| Maximum CAN-bus length | 800 m | per bus line |
| Maximum Number of Boxes | 25 | per bus line |
| Maximum Ethernet length (Cu) | 100 m | per segment (Over voltage protection necessary.) |
| Maximum Ethernet length (LWL) | 20 km | per segment |
General Data
| Ambient temperature | -25 °C...45 °C | No direct sun irradiation allowed. |
| Maximum altitude | 2000 m above sea level | without derating |
| Cooling type | Convection | |
| Protection class | IP66 | |
| Dimensions (H × W × D) | 590 mm × 260 mm × 700 mm | |
| Weight | approx. 20 kg | |
| Colour of cabinet | RAL7035 | Different colours on request. |
| EMI | Complies EN61000-6-2, EN61000-6-4 | |
| CE-conformity | Complies |
Features
| Over current and short circuit | Fuses in every positive and negative current path |
| protection | Touch screen with numerical and graphical display |
| Overvoltage protection | Class 1 and 2 surge arrester with monitor function |
| Arc protection | Test button allows to verify zero current condition for fuse removal. |
Options
| • Various mounting accessories for walls and pylons |
