Systems and methods for measuring the integrity of insulation components in energized or de-energized electrical systems. Using a digital modulation/demodulation system, an active monitoring system adds a modulated high frequency signal to an injected signal and demodulates the resulting signal to provide voltages and currents that are measured and used to determine the capacitances and power factors of the insulation components. Systems may be used for on-line detection and measurement of power factor and capacitance of electrical equipment such as transformers, reactors, and condenser type bushings. The present disclosure is especially applicable to the electrical power industry.