The string combiner box is primarily used for combining the electrical outputs of multiple strings of solar panels into a single high-value DC output, while the String monitoring box is used to monitor the performance of individual strings and provides real-time details and the operational status of each string/ array.

A typical string combiner box comprises of DC breaker, fuses for each string, surge protection devices, and connection devices so that they can act as a junction box for combining all string outputs. A typical string monitoring box includes a string monitoring controller unit, with integrated sensors like current sensors, voltage sensors, and temperature sensors depending on the parameters we need to monitor, and communication interfaces for data transmission (to SCADA). Ths String Monitoring units are connected to central Solar SCADA either through Hardwired communication cables or wireless technologies.

Typical parameters that can be measured from Solar SCADA include the following:

1. Weather Conditions
   1. Ambient Air temperature near the array field
   2. Control room temperature
   3. Wind speed and direction at the level of array plane
   4. Humidity
2. Solar Parameters
   1. Solar radiation incidental to array plane
   2. PV array output – Voltage, Current and Power
   3. String Voltage and Current
   4. Solar irradiation
   5. Temperature of solar panels
3. Inverter side
   1. DC voltage at the input of inverters
   2. AC output – Voltage, Current, Power, Frequency, PF
   3. MPPT Efficiency
   4. Inverter efficiency, status and fault detection
   5. Inverter status and alarm
4. Power Quality
   1. Harmonic Distortion
   2. Voltage Fluctuations
5. Grid Connection Parameters
   1. Energy delivered to the Grid in kWh
   2. Synchronization details
   3. Grid Voltage
   4. Grid Frequency and Phase
   5. Power at 11kV terminal
6. Communication status with field instruments and other relevant components