The Solar Plant Subsystem includes the Main Substation Unit, Peripheral Substation Units and String Combiner Boxes.
Main Substation Unit – MSSU
The MSSU is the heart of the Solar Plant Subsystem, installed in the main substation. It is connected to a variety of equipment that measure, monitor and control any desired parameter to networked intelligent devices along with various sensors and actuators. In detail:
- It gathers all necessary data, pre-processes and forwards the results over a network connection to the centralized Control Center servers.
- It may optionally undertake tasks relevant to the handling of the IP connection.
- It integrates with the alarm system to collect security events.
The MSSU is a modular system built around an embedded processor and various I/O units consisting of:
- An industrial computer based on a x86 or ARM processor
- An available number of I/O units that offer dedicated connectors to terminate I/O channels from the plant
- Interfaces that include analogue inputs and outputs, digital inputs and outputs, pulse inputs, serial and Ethernet interfaces
Peripheral Substation Unit – PSSU
A PSSU is optionally installed in each peripheral substation or inverter skid to extend the monitored signals. In detail:
- Just like the MSSU, the PSSU can be connected to a variety of measuring, monitoring and controlling equipment as well as various sensors and actuators.
- Together with the MSSU, the PSSU gathers all necessary data and pre-processes and forwards the results over the network connection to the centralized Control Center.
String Combiner Box – SCB
The Inaccess SCB monitors each individual string so as to achieve the best possible yield of the solar plant. The SCB is designed to be used in solar plants with central inverters in order to monitor and pin point malfunctions at photovoltaic string level. In addition, the SCB offers fused DC inputs, an output switch, SPDs and electronic equipment for string current monitoring. Main features include:
- Combines 8, 12, 16 or 24 PV strings
- Up to 1000V DC in measurement side
- Integrated DC load disconnector
- Integrated surge protection with monitored state
- 0-13.7A channel measurement range
- 1KHz sampling with on-board averaging
- Internal temperature measurement
- MODBUS over RS485 communication
- IP66 rated polycarbonate enclosure