I have updated to the latest bios now and set limit for battery charge to 80% in bios. But still the battery is charged up to 100%. This problem has appeared some updates ago, probably of KDE Plasma.
After bios update also I reinstalled tlpui but once again setting standby mode and waking up the PC ends into a blackscreen. Only hard shut down helps for restart.
There is definitely something wrong with the power management of KDE Plasma.