What does the integral of reactive power over time measure?

The integral of reactive power over time measures reactive energy. Reactive power, measured in volt-amperes reactive (VAR), represents the power that alternates between the source and the load, not doing any real work but instead sustaining the electric and magnetic fields in the system. By integrating reactive power over time, you quantify how much reactive power has been used or produced during a specific period, which is termed reactive energy, typically measured in volt-amperes reactive-hours (VARh).

This concept is crucial in understanding the behavior of electrical systems, particularly in AC circuits where reactive components like inductors and capacitors are present. Reactive energy is essential for the operation of many electrical devices, but it does not translate to actual work done in the way that active power does. In power system analysis and operation, managing reactive energy is vital for maintaining system stability, voltage levels, and overall efficiency.