Ground faults are a common cause of a tripped or faulty circuit breaker. If you ever turn on a breaker and immediately hear a loud pop or see smoke coming from it, you probably just experienced a ground fault.
A ground fault is when a hot wire touches a grounded metal portion of your electrical system. For example, when a cable’s insulation has been damaged and the copper shows through; it can ground fault to the metal rigid conduit it was installed in. When a hot wire is damaged and touches the grounded metal; you will experience a ground fault, which trips the circuit breaker and makes a loud pop depending on the amperage.
In short (no pun intended), the electricity travels to the ground (usually your conduit) instead of to your appliances or equipment. This issue is usually caused by a lack of maintenance or the age of your electrical system. It may also be caused by a pinched wire, which could mean the wire was installed improperly.
We’ve experienced this on older systems that have poor condition wire where the insulation is dry rotted. The solution almost always requires re-wiring or wire replacement depending on the root cause.
The simplest way to diagnose a ground fault is with a continuity test. Specifically from your hot wires to the ground/conduit. If you have continuity between your ground/conduit and your ungrounded conductors, this means there is a ground fault present.
The next step, especially on a large industrial application, is to conduct a megger test. This will verify any voltage leaks in the wiring where the insulation is damaged. If you are having large voltage leaks, then the wire will need to be replaced.
In summary, ground faults can be extremely dangerous and should be treated with caution. Always test ANY electrical equipment thoroughly before energizing. Especially when dealing with high amperage or old/damaged wiring.
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