What should the additional grounding point of a service transformer be connected to?

The additional grounding point of a service transformer should ideally be connected to a high impedance grounded neutral system. In a high impedance grounding setup, the neutral is connected to ground through a resistor or reactance, which limits the ground fault current to a low level. This approach enhances safety and minimizes equipment damage because it allows for fault detection while maintaining system stability during a ground fault.

By connecting the grounding point this way, the protection devices can operate correctly without tripping unnecessarily from transient over-voltages or minor ground faults. This method is particularly beneficial in systems where continuity of service is essential, such as in critical infrastructure. Furthermore, a high impedance system helps to prevent severe voltage rises during a fault condition, thereby protecting both the transformer and the associated electrical equipment.

In contrast, options that suggest connecting directly to ground without impedance or to a low impedance system can result in higher fault currents that may pose safety hazards and increase the risk of equipment damage. Hence, the choice of connecting to a high impedance grounded neutral system is optimal for effectively managing ground faults while maintaining the system's operational integrity.