Comment 6 for bug 1474534

I have almost the same issue except the dim starts working after 20 seconds. I tried many solutions

Kubuntu 16.04 64-bit

1. Using GUI:
1.1. System Settings >> Energy Saving >> Uncheck Dim screen
1.2. System Settings >> Energy Saving >> Dim screen (360 min)
1.3. Disabling Power Management service: System Settings >> Autostart >> Background Services >> Uncheck Power Management

2. Using command line
2.1. Installing xscreensaver and configure the screensaver duration for longer period or disable it
2.2. xset s off
2.3. xset s noblank -dpms
2.4. Add the following to ~/.kde/share/config/powermanagementprofilesrc
[Battery][RunScript]
idleTime=60000
scriptCommand=/usr/local/bin/batgoverner
scriptPhase=0

[Battery][SuspendSession]
idleTime=3600000
suspendType=2

[LowBattery]
icon=battery-low

[LowBattery][BrightnessControl]
value=30

[LowBattery][DPMSControl]
idleTime=120

[LowBattery][DimDisplay]
idleTime=60000

[LowBattery][HandleButtonEvents]
lidAction=1
powerButtonAction=2

I saw poeple complain this issue since 2013!