Ungrounded power system overview
This system varies from country to country, including some applications where this system is mandated, such as hospital and the naval applications. This system is typically used in instances where the unavailability of power could result in lost production or incur significant downtime costs. Other potential applications are when there is a need to minimize the risk of fire and explosion. Lastly, this system is chosen in certain cases because it can facilitate preventive and corrective maintenance operations.
The system transformer’s neutral is isolated from earth, or there is a high impedance between the neutral and earth, while the electrical load frames are earthed. This isolates the transformer and the load such that if the first fault occurs there is no loop for shorting current to flow, allowing the system to continue to operate normally without hazard to people and equipment. This system must have very low network capacitance to ensure that the first fault current cannot generate significant voltage. However, the faulty circuit must be detected and repaired before a second fault occurs. Because this system can tolerate an initial fault, maintenance operations can be improved and carried out in a safe and convenient manner.