If the ground conductor runs through the zero-sequence CT with current carrying conductors, what is the likely outcome?

When the ground conductor runs through the zero-sequence current transformer (CT) along with current-carrying conductors, an issue arises where ground fault protection may not function as intended. The zero-sequence CT is designed to sense the difference in current between the phase conductors and the ground conductor to detect ground faults. If the ground conductor is included with the phase conductors, the CT measures the combined current, potentially leading to misinterpretation.

In a typical situation, the ground fault protection function relies on the CT to detect an imbalance in current, which indicates that some current is leaking to ground, a sign of a ground fault. However, if the ground conductor is not separated and runs together with the phase conductors, it may result in no net imbalance being detected by the CT during actual ground fault conditions. Thus, without the ability to accurately sense ground fault currents, the ground fault protection won't function correctly.

This understanding means that if the ground conductor is improperly positioned within the zero-sequence CT, it essentially nullifies the mechanism that should alert the system to a fault condition, leading to inadequate protective measures against ground faults.