Ground-fault protection for direct current circuits

A ground fault detection system for detecting ground faults in a power transmission circuit for powering a load with direct-current power, the system comprising:

• a common mode union, wherein a first portion of the common mode union is connected to a positive source of a power supply and a second portion of the common mode union is connected to a negative source of the power supply, wherein:
• the positive source has a more positive terminal and a more negative terminal, and the negative source has a more negative terminal and a more positive terminal;
• and
• the first portion of the common mode union is attached to the more negative terminal of the positive source and the second portion of the common mode union is attached to the more positive terminal of the negative source;
• a power supply symmetry circuit connected to the common mode union, wherein the power supply symmetry circuit is configured to generate a symmetry signal indicative of a symmetry of voltages in the power transmission circuit;
• an offset threshold comparator circuit configured to receive the symmetry signal, wherein the offset threshold comparator circuit is further configured to compare the symmetry signal from the power supply symmetry circuit to a threshold voltage value and generate a ground-fault signal indicating a ground fault when the symmetry signal exceeds the threshold voltage value;
• and
• a local load control circuit configured to receive the ground fault signal, wherein the local load control circuit is further configured to remove power from the load based on the received ground-fault signal.

A ground fault detection system for detecting ground faults in a power transmission circuit powering a load, the system comprising:

• a common mode union, wherein a first portion of the common mode union is connected to a positive source of a power supply and a second portion of the common mode union is connected to a negative source of the power supply, wherein:
• the positive source has a more positive terminal and a more negative terminal, and the negative source has a more negative terminal and a more positive terminal;
• and
• the first portion of the common mode union is attached to the more negative terminal of the positive source and the second portion of the common mode union is attached to the more positive terminal of the negative source;
• a power supply symmetry circuit connected to the common mode union, wherein the power supply symmetry circuit is configured to detect symmetry of voltages in a power transmission circuit;
• an offset threshold comparator circuit connected to the power supply symmetry circuit and configured to receive a signal from the power supply symmetry circuit, wherein the offset threshold comparator circuit is further configured to compare the signal from the power supply symmetry circuit to a threshold voltage value and generate a ground-fault signal indicating a ground fault when the signal from the power supply symmetry circuit exceeds the threshold voltage value;
• an over-current detection circuit connected to the common mode union, the over-current detection circuit configured to detect an over-current event;
• an over-voltage detection circuit connected to the power transmission circuit, the over-voltage detection circuit configured to detect an over-voltage event;
• and
• a local load control circuit configured to receive a signal from the offset threshold comparator circuit, a signal from the over-current detection circuit, and a signal from the over-voltage detection circuit, wherein the local load control circuit is further configured to open the power transmission circuit based on the received signals.