Power or voltage oscillation damping in a power transmission system

A device for providing improved control of power or voltage oscillation damping in a power transmission system, comprising:

• a magnitude obtaining element configured to obtain an instantaneous magnitude of a signal (|ΔP|) representing an oscillation deviating from steady state quantities in at least one element of the power transmission system, ΔP being an oscillatory component of a system operation reflecting signal (P), which P reflects a measured power property of the at least one system element,
• a slope investigating element configured to determine the rate of change of the signal and,
• a first processing block comprising an integrating element configured to integrate the instantaneous magnitude with an integrating factor that is based on the determined rate of change, said first processing block being further configured to form a phase compensation angle based on the integrated instantaneous magnitude in a damping control signal generating unit in order to provide power or voltage oscillation damping of the system.