# In brief how to calculate mismatch? Part 2

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Hello again,

You guys have just developped a very atractive tool to calculate mismatch at a glance it looks impressive, but i need to understand it in order to use it correctly. I have a couple of questions: We have in the old tool mismatch in Current & Voltage, what kind of mismatch does this tool calculate? In label 2 it shows voltage mismatch, which is the same as the old tool right? In the last label it appears 2 more results: Average power loss...is this only ohmic loss?? and the other mismatch itself...is this only mismatch among strings? all this detailed study refers to STRING mismatch right?

So, summing up, we have 3 mismatches, 2 of them are calculated in the old tool and one with the new (strings). The new tool also gives academic examples of explanation of phenomenom of mismtach and calculates voltage mismatch (but this is redundant as the old tool also calculates it). Am i right? am i missing something for taking advantage of these tools?

Many thanx Best R

Jose

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• 2 weeks later...

The old tool concerns mismatch between individual modules.

For the current, the mismatch is mainly due to the worst current module in each string.

For the voltage, the differences in voltage add-up for each module, this means that if you have a given RMS distribution for all modules, the voltage difference for a full string will statistically be RMS / sqrt(n), where n is the number of modules in series. So the mismatch in voltage between strings is much lower.

The new tool aims to evaluate the mismatch in voltage between strings.

When dealing with string voltages, the average power loss due to the mismatch is the difference between the sum of the MPP powers of each string, and the effective resulting voltage when mixing the I/V curves. Here no effect of the "worst" string: the mismatch loss is much lower. These voltage mismatches may be due to:

- RMS values of individual modules (evaluated in the previous tool),

- Array temperature differences,

- Wiring resistances of different string lengths.

This tool tries to give ways for the evaluation of realistic wiring resistances according to the tables layout and inverters position.

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Thank you André, i was a little bit wrong!. Anyway...in the new tool it exists 2 results, one direct (voltage mismath between strings) and at the end it says "wires and results" and then it says another mismatch result, which is different to the first i mention, what this result stand for? should we sum or additionate both?