Abstract: A digital voltage detector uses a running average to detect utility service disturbances in real time. An isolation transformer taps the main electrical AC power supply line and provides an analog voltage waveform to a system controller. The analog waveform is sampled digitally in real time, and the samples are squared to create respective instantaneous squared voltage values. A running average is kept of the instantaneous squared voltage values for a preselected period of time, preferably one half-cycle for the main power supply waveform. The running average is compared to a preselected under-voltage threshold value and a preselected over-voltage threshold value, and a disturbance detection signal is generated if the running average violates either threshold value. The disturbance detection signal is preferably used to activate a standby electrical AC power supply, and contemporaneously to disable the main electric AC power supply.

Abstract: An electric load levelling system includes a plurality of individual modules for storing and supplying AC electrical power. Each module is preferably contained within a separate enclosure and includes a plurality of individual electrochemical storage cells for storing DC electrical energy. Each enclosure includes a power conversion mechanism for converting input AC power for storage in the enclosed DC cells, and output DC power from the cells to AC for supply to an input/output line. The system is capable of storing electrical energy during periods of off-peak demand, and outputting such stored energy during periods of peak demand. The individual modules function as an "AC battery" having an AC input and output, and are adapted for mass production and ease of interchangeability.