Patent ID: 8310105

Claim:
A protective, anti-islanding device for use with one or more electrical grid-interactive generators and comprising; (i) a means of periodically perturbing or attempting to disturb the stability, balance, voltage, frequency or line-to-line phase-relationships of an electrical grid at a point of common coupling, with respect to power transfer between a grid-interactive generator, an electrical grid source and a grid-connected load, (ii) a means of observing an effect of said perturbing or attempting to disturb stability, balance, voltage, frequency or line-to-line phase-relationships of said electrical grid, (iii) a means of determining if said effect of perturbing or attempting to disturb said stability, balance, voltage, frequency or line-to-line phase-relationships of said electrical grid is characteristic of and therefore indicates an islanding condition or more succinctly, if said effect of perturbing or attempting to disturb said stability, balance, voltage, frequency or line-to-line phase-relationships of said electrical grid indicates that the electrical grid-interactive generator is supplying the grid-connected load in the absence of the electrical grid source, and (iv) a means of disconnecting the electrical grid-interactive generator from said point of common coupling or a means of shutting down the electrical grid-interactive generator if an islanding condition is determined and where said means of perturbing or attempting to disturb said stability, balance, voltage, frequency or line-to-line phase-relationships of the electrical grid further comprises a controllable switch, a reactive load in series with the switch, and a control circuit where said control circuit further comprises a means of periodically issuing commands to close said switch to couple said reactive load at said point of common coupling for some period of time.