Ground faults on large ampere services are always of the magnitude that the phase OCPD provides suitable protection against ground faults. Which statement best reflects this?

Ground faults on large ampere services are always of the magnitude that the phase OCPD provides suitable protection against ground faults. Which statement best reflects this?

• A. True
• B. False
• C. Sometimes
• D. Not Enough Information

Answer: (B)

Ground-fault current is governed by the impedance of the fault path, not by the phase overcurrent device alone. The phase OCPD protects conductors against excessive current during phase short circuits, but it does not guarantee protection for ground faults. If the path to ground has high impedance, the ground-fault current can be small and may not trip the phase OCPD; conversely, certain configurations can produce larger currents, but there is no assurance that the phase device will always provide suitable protection against ground faults. So the statement isn’t always true—additional ground-fault protection or leakage protection may be needed.

Ground-fault current is governed by the impedance of the fault path, not by the phase overcurrent device alone. The phase OCPD protects conductors against excessive current during phase short circuits, but it does not guarantee protection for ground faults. If the path to ground has high impedance, the ground-fault current can be small and may not trip the phase OCPD; conversely, certain configurations can produce larger currents, but there is no assurance that the phase device will always provide suitable protection against ground faults. So the statement isn’t always true—additional ground-fault protection or leakage protection may be needed.