Reactive power is the AC power that moves back and forth between electric and magnetic fields in a network. Measured in VARs, it does not deliver useful work like real power, but it is essential for keeping voltage within a stable range and for supporting motors, transformers, filters, and converter equipment.
In cyber security, reactive power matters because attackers often target the controls and telemetry that manage voltage and power factor. Unauthorized switching of capacitor banks, inverter setpoints, or filter banks can push a grid toward under- or over-voltage conditions. Spoofed sensor data can hide that change from operators. Defenders watch reactive power flows for anomalies, compare them with active power and voltage readings, and use SCADA alarms to spot manipulation early.