Method and apparatus for control and detection in resistance grounded electrical systems

A high resistance grounding system, comprising

• a neutral conductor configured to connect to an electrical system that provides three phase AC power of at least about 480 volts to industrial machinery;
• a phase conductor configured to connect to the electrical system;
• a ground connection;
• a neutral grounding resistor having a high resistive impedance connected between the neutral conductor and the ground connection and having a resistance selected to limit the ground fault current flow from the ground through the resistor to the neutral conductor to a value in a range that is substantially equal to or slightly greater than the capacitive charging current of the system, wherein the resistance is selected to provide overvoltage protection such that the electrical system and industrial machinery can be continually operated even in the presence of a ground fault;
• and
• a digital processor configured to determine whether a ground fault has occurred by monitoring an electrical parameter of the high resistance resistor relating to the current flowing from the ground through the high resistance resistor to the neutral conductor;
• wherein the grounding system is configured to allow the electrical system and industrial machinery to be continually operated in the presence of a ground fault.

A ground fault detector system, comprising:

• a neutral grounding resistor connected between the neutral and ground of a monitored electrical system and having a resistance selected to limit the ground fault current flow from the ground through the resistor to the neutral to a value in a range that is substantially equal to or slightly greater than the capacitive charging current of the electrical system, wherein the resistance is selected to provide overvoltage protection such that the electrical system can be continually operated even in the presence of a ground fault;
• a digital detection circuit configured to determine a ground fault condition from an electrical parameter of the resistor relating to the current flow from the ground through the resistor to the neutral;
• a digital communication port configured for communication with an external digital data storage apparatus;
• and
• an external digital data storage apparatus in communication with the digital detection circuit via the digital communication port and configured to receive signals from the digital detection circuit indicating the values of the electrical parameter over a time period.

A ground fault detector system, comprising:

• a neutral grounding resistor connected between the neutral and ground of a monitored electrical system and having a resistance selected to limit the ground fault current flow from the ground through the resistor to the neutral to a value in a range that is substantially equal to or slightly greater than the capacitive charging current of the electrical system, wherein the resistance is selected to provide overvoltage protection such that the electrical system can be continually operated even in the presence of a ground fault;
• a ground input configured to connect to the ground of the monitored electrical system;
• a phase input configured to connect to the phase of the monitored electrical system;
• and
• a detection circuit configured to determine a ground fault condition from an electrical parameter of the resistor and configured to detect a high harmonic condition of the electrical parameter.