Oh, I just saw that you want to run 15m. For PoE, I would recommend a Cat.7 cable like this:
Lindy network cable (15m, S/FTP, Cat. 7). You should not have any problems with this.
Cat.5 cables are also more reliable at this length than Cat.6 because their wire cross-section is larger.
Normally it looks like this.
Cat.5 : AWG24/23 0.205 /0.258 mm²
Cat.6 : AWG26 0,129 mm²
Cat.7: AWG23/22 0.258 /0.326 mm²
The Cat.6 cable may be too narrow.
Greetings John