Skip to main content

Greenbyte Documentation

Lost Production to String Downtime (Combiner Box)

Lost Production to String Downtime (Combiner Box) returns the total estimated loss due to strings that are not producing for a combiner box.

The loss is calculated by comparing each String DC Normalized Current with the Reference Current Normalized for the combiner box. The calculation is based on the assumption that all String DC Normalized Currents connected to one combiner box should perform similarly, and if a string is not producing anything while the other strings are, the loss is allocated to Lost Production to String Downtime.

This calculation also exists on the inverter level, where the downtime losses on the combiner box level are accumulated to the parent inverter, see Lost Production to String Downtime (Inverter).

Technology

Solar

Remarks

Required signals:

The result of this calculation is not available for the current date before the sunset at the site in question.

No loss will be allocated to the combiner box if all strings on the combiner box are simultaneously not producing. This is a result of the assumption that all String DC Normalized Currents connected to one combiner box should perform similarly.

Equation
Lost_Production_to_String_Downtime__Combiner_Box__-_Equation_1.png

Where:

LPistring

is the lost production for string i

Cistring

is the rating of string i (in Ampere)

IDCNorm,reference

is the Reference Current Normalized for the combiner box

IiDCNorm

is the String DC Normalized Current for string i

V

is voltage

T

is the device resolution in hours

The lost production for each string is calculated as described by the equation above. To avoid including losses due to short-lived differences between the string outputs, for example, due to clouds passing or temporary data discrepancy, the lost production for each string is filtered. The filter removes losses that are not present for a large part of the day (sunrise to sunset).

The lost production for string i is then categorized as lost production to downtime or performance, depending on if the string is producing.

  • If the string is not producing anything at all, the loss for this string is accounted for as Lost Production to String Downtime.

  • If the string is producing, though less than the reference, the loss for this string is accounted for as Lost Production to String Performance.

Lost_Production_to_String_Downtime__Combiner_Box__-_Equation_2.png
Lost_Production_to_String_Downtime__Combiner_Box__-_Equation_3.png

The total Lost Production to String Downtime is calculated by summing the loss from the individual strings.

Lost_Production_to_String_Downtime__Combiner_Box__-_Equation_4.png
Inputs
Lost_Production_to_String_Downtime__Combiner_Box__-_Inputs.png
Usage Example
Lost_Production_to_String_Downtime__Combiner_Box__-_Usage_Example.png