100 led string to 2 X 50 led stings
We're expecting a wiring configuration something like this.







simulate this circuit &ndash; Schematic created using CircuitLab

(Don't mind the numbers on the LEDs.)

Your comments on the original post don't quite add up.


You can see on the schematic above that we have three wires to the first two LEDs and then five and then three again. This matches your description except that you say it returns to three wires after 25 LEDs. As this isn't the mid-point of the string it doesn't make sense unless the pattern repeats as shown below.








simulate this circuit

Here we have eight strings of 12 or 13 LEDs. Four strings are wired in parallel on each circuit. This makes a bit more sense as 31 V should be about enough to power 12 or 13 white LEDs.

Have another look at your lights and see if the wires to 3 to first two lights, then 5 for a while, then 3 for two lights, then 5 ...

If this is the case we should be able to cut wherever there are three wires. We need some more information from you.