In the KDE Control Centre, in the Laptop Battery, Power Control tab, there is the option "Don't act if LAV is>". I'd guess that this prevents the power saving mode from starting if the CPU is loaded. But what does "LAV" mean and what are the units?
Load average (i.e. how occupied is your CPU with handling the running processes?).
Have a look at uptime command to get a feeling how these values look like. The three are standing for the load average of the last 1 minute, last 5 minutes and the last 15 minutes.