Ground fault sensor

A ground fault detector for connection in a pair of electrical power lines and comprising:

• a switch connected in series in one of said lines;
• actuating means in the form of a piezo-electric element of the kind that changes dimensions when subjected to an electric field for actuating said switch;
• electrically chargeable means chargeable to create an electric field in said piezo-electric element sufficient for rendering said actuating means operable to actuate said switch;
• charging means responsive to differences between the electrical state of the lines of said pair of lines for charging said electrically chargeable means;
• and
• means for discharging said electrically chargeable means at a selected discharge rate.

A ground fault detector for connection in a pair of electrical power lines and comprising:

• a switch connected in series in one of said lines;
• actuating means in the form of a piezo-electric element of the kind that changes dimensions when subjected to an electric field for actuating said switch;
• electrically chargeable means chargeable to create an electric field in said piezo-electric element sufficient for rendering said actuating means operable to actuate said switch;
• charging means responsive to differences between the electrical state of the lines of said pair of lines for charging said electrically chargeable means;
• said charging means comprising means for converting alternating electrical differentials in the state of said lines to unidirectional electrical current and in which said piezo-electric element is a multimorph;
• and
• a time delay discharge resistor connected in parallel with said multimorph.

A ground fault detector for connection in power conductors extending from a source of electrical power at one of which conductors includes a switch connected in series therewith, comprising:

• a multimorph responsive to currents applied thereto as an incident to imbalance in said conductors to charge its physical dimensions;
• means responsive to such change in physical dimensions for actuating said switch;
• and
• means for discharging said multimporph at a selected rate whereby said switch is reactuated following a time interval.

The method of protecting persons who come in contact with the hot side of a pair of electrical power conductors and ground which comprises the steps of:

• a. measuring and comparing the electrical state of the conductors of said pair;
• b. altering the electrical charge of a multimorph upon finding a differential in the electrical state of said conductors;
• c. opening said hot side when the charge on said multimorph exceeds a selected magnitude;
• d. discharging said multimorph at a selected rate such that its charge falls below said selected magnitude and reclosing said hot side;
• and
• e. reopening said hot side if, at the time of reclosing, there is a differential in the electrical state of said conductors.

A ground fault detector for connection in a pair of electrical power lines and comprising:

• interruption means for interrupting said power lines;
• actuating means of a kind that changes dimensions when subjected to an electrically created field for actuating said interrupting means;
• field creating means for creating a field electrically to render said actuating means operable to actuate said interruption means;
• means responsive to differences between the electrical state of said power lines for rendering said field creating means effective to create a field;
• means for dissipating said electrically created field;
• said actuating means being effective to reactivate said interrupting means to terminate interruption of said power lines upon dissipation of said field;
• and
• means for dissipating said electrically created field sufficiently to reactuate said actuating means after a selected time delay.