In a 3-phase, 3-wire delta service, what is the required ampacity of the grounded conductor?

In a 3-phase, 3-wire delta service, the grounded conductor plays an important role in providing a return path for fault currents and ensuring system stability. The requirement that the grounded conductor must not be less than the ampacity of the ungrounded conductors is crucial to prevent overheating and potential failure during normal operating conditions or fault scenarios.

When a fault occurs in a delta system, the grounded conductor is responsible for carrying fault current back to the supply, which can be significant. If the grounded conductor is undersized compared to the ungrounded conductors, it may not be able to handle the fault current effectively, leading to overheating and possible damage. Therefore, the grounding conductor must have an ampacity that is equal to or greater than that of the ungrounded conductors to ensure safety and reliability.

This requirement aligns with the principles of grounding and bonding, which aim to enhance the safety of electrical systems. Having an appropriately sized grounded conductor provides a robust means of earthing, allowing for effective fault current management and reducing the risk of electric shock or fire.